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muscles
remain attached to its deep surface. The remnant of the embryonic left siderably in size. It may be larger on one side than on the other, some-
umbilical vein forms the round ligament of the liver. The obliterated times absent on one or both sides, or rarely doubled.
umbilical arteries form the medial umbilical ligaments on the under-
surface of the anterior abdominal wall and are covered by the medial Vascular supply Pyramidalis is supplied by branches of the inferior
umbilical folds. The partially obliterated remains of the urachus persist epigastric artery. A small artery frequently crosses the midline posterior
as the median umbilical ligament and fold. Both congenital and to the belly of the muscle to anastomose with the contralateral vessel.
acquired umbilical hernias are common; most childhood umbilical
hernias close spontaneously and do not require surgical repair. The Innervation Pyramidalis is usually supplied by the terminal branches
umbilicus is the most common site for laparoscopic access to the peri- of the subcostal nerve, the ventral ramus of T12, but it may be inner-
toneal cavity. vated wholly or in part by fibres from L1 travelling in the subcostal or
ilioinguinal nerves (Tokita 2006).
divarication of the recti
Actions Pyramidalis contributes to tensing the lower linea alba but
Thinning and widening of the linea alba in the upper abdomen may
is of doubtful physiological significance.
occur, most commonly as a result of pregnancy, obesity or chronic
straining (Akram and Matzen 2014). Abdominal viscera protrude
beneath the thinned tissue as a broad midline bulge, particularly when External oblique
intra-abdominal pressure is raised, and the recti become widely sepa- Attachments External oblique is the largest and most superficial of
rated or divaricated. This state is not true herniation because all the
the three anterolateral abdominal muscles (Fig. 61.11). It curves around
layers of the abdominal wall in the region are intact.
the lateral and anterior parts of the abdomen and is attached to the
external surfaces and inferior borders of the lower eight ribs. The attach-
Pyramidalis
ments rapidly become muscular and interdigitate with the lower fibres
Attachments Pyramidalis is a triangular muscle that lies in front of of serratus anterior and latissimus dorsi along an oblique line that
the lower part of rectus abdominis within the rectus sheath. It is attached extends downwards and backwards. The upper attachments are close to
by tendinous fibres to the anterosuperior margin of the pubis and to the cartilages of the corresponding ribs, the middle ones arise from the
ligamentous fibres in front of the symphysis. The muscle diminishes in ribs at some distance from their cartilages, and the lowest are close to
size as it runs upwards, and ends in a pointed apex that is attached the apex of the cartilage of the twelfth rib. The fibres of external oblique
medially to the linea alba. This attachment often lies midway between diverge as they pass to their lower attachments. Those from the lower
the umbilicus and pubis, but may occur higher. The muscle varies con- two ribs pass nearly vertically downwards and attach to the anterior half
Fig. 61.11 The left anterolateral
abdominal wall muscles.
Pectoralis major
Serratus anterior
Latissimus dorsi
Linea alba
Rectus sheath, anterior layer
External oblique
Tendinous intersections
Linea semilunaris
External oblique aponeurosis Lumbar triangle
Crest of ilium
Anterior superior iliac spine
Gluteus medius
Inguinal ligament
Gluteus maximus
Superficial inguinal ring
Spermatic cord
Tensor fasciae latae
Femoral fascia | 1,496 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Anterior AbdominAl wAll
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or more of the outer lip of the iliac crest. The middle and upper fibres Innervation Internal oblique is innervated by the terminal branches
pass downwards and forwards, and end in the anterior aponeurosis, of the lower five intercostal nerves and the subcostal nerve from the
whose fibres cross the midline (see above). The junction between ventral rami of the lower six thoracic spinal nerves. In addition, it
muscle and aponeurosis extends along a vertical line from the ninth receives a small contribution from the iliohypogastric and ilioinguinal
costal cartilage to just below the level of the umbilicus; muscle fibres nerves derived from the ventral ramus of the first lumbar spinal nerve.
do not usually descend beyond a line from the anterior superior iliac
spine to the umbilicus. External oblique has a free posterior border. Actions Internal oblique contributes to the maintenance of abdomi-
The inguinal ligament is formed by the inferior margin of the nal tone, increasing intra-abdominal pressure, and lateral flexion of the
aponeu rosis of external oblique extending between the anterior supe- trunk against resistance.
rior iliac spine and the pubic tubercle. The fibres of the aponeurosis of
Transversus abdominis
external oblique are not parallel to the long axis of the inguinal liga-
ment; they approach the ligament obliquely at an angle of 10–20° and Attachments Transversus abdominis is the deepest of the anterola-
then turn medially to run along the ligament to reach the pubic tubercle teral abdominal muscles (Fig. 61.12). It is attached to the iliopectineal
(Lytle 1974). The deepest fibres of the aponeurosis spread out postero- arch deep to the lateral third of the inguinal ligament, the anterior two-
medially to insert into the pectineal line. thirds of the inner lip of the anterior segment of the iliac crest, the
The upper and lower rib attachments of the muscle may be absent. thoracolumbar fascia between the iliac crest and the twelfth rib, and the
Digitations or even the entire muscle may be duplicated. The upper internal aspects of the lower six costal cartilages. The costal attachments
attachments of the muscle are sometimes continuous with pectoralis interdigitate with those of the diaphragm. The muscle ends anteriorly
major or serratus anterior. in an aponeurosis; the lower fibres of the aponeurosis curve downwards
and medially, together with those of the aponeurosis of internal oblique,
Vascular supply External oblique is mainly supplied by branches and insert into the pubic crest and pectineal line to form the conjoint
from the lower posterior intercostal and subcostal arteries above and tendon. A few muscle fibres may run from the lower border of trans-
the deep circumflex iliac artery below. There are additional smaller versus abdominis to the inguinal ligament and reinforce the interfoveo-
contributions (Schlenz et al 1999). lar ligament (see above). The remainder of the aponeurosis passes
medially and the fibres decussate at, and blend with, the linea alba. The
Innervation External oblique is innervated by the terminal branches upper costal and anterior iliac fibres of transversus abdominis are short
of the lower five intercostal nerves and the subcostal nerve from the and the thoracolumbar fibres are the longest. Near the xiphoid process,
ventral rami of the lower six thoracic spinal nerves. the aponeurosis is formed only a few centimetres from the linea alba
and so the muscular part of transversus abdominis extends behind
Actions External oblique contributes to the maintenance of abdomi- rectus abdominis into the posterior layer of the rectus sheath. The
nal tone, increasing intra-abdominal pressure, and lateral flexion of the medial edge of the muscle, at the origin of the aponeurosis, curves
trunk against resistance. downwards and laterally, and is furthest from the lateral edge of the
rectus sheath at the level of the umbilicus. It then curves downwards
inguinal ligament and medially towards the superficial inguinal ring.
The inguinal ligament is the thick lower border of the aponeurosis of Occasional defects may occur in the lower muscular and aponeurotic
external oblique that stretches between the anterior superior iliac spine parts of both internal oblique and transversus abdominis. The two
and the pubic tubercle. Its medial half is curled in on itself, forming muscles are sometimes fused and, rarely, transversus abdominis may be
the gutter-like ‘floor’ of the inguinal canal. The ligament is not exactly absent.
linear but has an inferior and an anterior convexity. At its lower border,
it is fused with the fascia lata. Laterally, it is fused with the iliopsoas Vascular supply Transversus abdominis is supplied by branches
fascia (Lytle 1974). At the medial end of the inguinal ligament, near from the lower posterior intercostal and subcostal arteries, the superior
its site of attachment to the pubic tubercle, some of its fibres extend and inferior epigastric arteries, the superficial and deep circumflex iliac
posteriorly and laterally to attach to the pectineal line, forming the arteries and the posterior lumbar arteries.
triangular, shelf-like lacunar ligament. Other fibres pass upwards and
medially behind the superficial inguinal ring and external oblique Innervation Transversus abdominis is innervated by the terminal
aponeurosis to join the rectus sheath and linea alba; these constitute branches of the lower five intercostal nerves, the subcostal nerve and
the reflected part of the inguinal ligament (Tubbs et al 2009). Fibres the iliohypogastric and ilioinguinal nerves. These arise from the ventral
from both sides decussate in the linea alba. rami of the lower six thoracic and first lumbar spinal nerves.
Internal oblique Actions Transversus abdominis contributes mainly to the mainte-
Attachments Internal oblique lies deep to external oblique for most nance of abdominal tone and increasing intra-abdominal pressure.
of its course (see Fig. 61.6). It is thinner and less bulky than external
Conjoint tendon
oblique. Its fibres are traditionally stated to arise from the lateral two-
thirds of the inguinal ligament but, in fact, arise from the corresponding The conjoint tendon is formed from the lower fibres of internal oblique
length of a slightly deeper structure known as the iliopectineal arch and the lower part of the aponeurosis of transversus abdominis. It is
(Acland 2008), a thickened band of iliopsoas fascia that passes down- attached to the pubic crest and extends to a variable extent along the
wards and medially from the anterior superior iliac spine to the ilio- pectineal line (see Fig. 61.16). It descends behind the superficial
pectineal eminence of the hip bone. Further laterally, internal oblique inguinal ring and acts to strengthen the medial portion of the posterior
is attached to the anterior two-thirds of the iliac crest deep to the attach- wall of the inguinal canal. Medially, the upper fibres of the tendon fuse
ment of external oblique. Posteriorly, some fibres are attached to the with the anterior wall of the rectus sheath, and laterally, some fibres
thoracolumbar fascia. The fibres originating from the posterior end of may blend with the interfoveolar ligament.
the iliac attachment pass obliquely upwards and are attached to the Cremaster
inferior borders and tips of the lower three or four ribs and their carti-
Attachments Cremaster consists of loosely arranged muscle fasciculi
lages. Here, the attachments merge with those of the internal intercostal
lying along the spermatic cord or round ligament of the uterus. It is
muscles. The uppermost fibres form a short, free superior border. The
variable in thickness but thickest in young men. Together with connec-
fibres from the anterior end of the iliac crest diverge and end in the
tive tissue, it forms an incomplete coating around the spermatic cord,
anterior aponeurosis, which gradually broadens from below upwards.
known as the cremasteric fascia, which extends down around the testis
The uppermost part of the aponeurosis is attached to the cartilages
deep to the external spermatic fascia. The muscle consists of a lateral
of the seventh, eighth and ninth ribs. The fibres that originate adjacent
part that arises mainly from the inferomedial border of internal oblique
to the inguinal ligament arch downwards and medially across the sper-
and transversus abdominis but also has attachments to the middle of
matic cord in the male and the round ligament of the uterus in the
the inguinal ligament, and a medial part attached to the pubic tubercle,
female. They become tendinous, fuse with the corresponding part of
lateral pubic crest and the lower border of transversus abdominis;
the aponeurosis of transversus abdominis, and attach to the pubic crest
this part is variably developed, and may be absent (Shafik 1977). The
and medial part of the pectineal line, forming the conjoint tendon.
longitudinal muscle fibres spread out over the spermatic cord as it
approaches the superficial inguinal ring. Cremaster is composed of both
Vascular supply Internal oblique is mainly supplied by branches
striated and smooth muscle fibre bundles (Kayalioglu et al 2008).
from the lower posterior intercostal and subcostal arteries, the inferior
epigastric artery, and the deep circumflex iliac artery. There are several Vascular supply Cremaster is supplied by the cremasteric artery, a
smaller contributions (Yang et al 2003). branch of the inferior epigastric artery. | 1,497 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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muscles
Fig. 61.12 The left transversus
abdominis. The aponeurosis of
transversus abdominis fuses into
the posterior layer of the rectus
Serratus anterior sheath above the arcuate line. The
position of the lateral border of
Latissimus dorsi rectus abdominis is shown by the
dotted white line.
Cut edge of posterior lamina of
aponeurosis of internal oblique
Posterior lamina of sheath Thoracolumbar fascia
of rectus abdominis
Transversus abdominis
Cut edge of aponeurosis of
internal oblique
Arcuate line
Cut edge of internal oblique
Transversalis fascia
Cut edge of aponeurosis
Rectus abdominis (cut) of external oblique
Anterior superior iliac spine
Cut edge of aponeurosis
of external oblique
Inguinal ligament
Transversalis fascia
Spermatic cord
Innervation Cremaster is innervated by the genital branch of the
genitofemoral nerve, derived from the first and second lumbar spinal
nerves.
Actions Cremaster pulls the testis up towards the superficial inguinal
ring. Although it contains striated muscle fibres, it is not usually under
voluntary control. Stroking the skin of the medial side of the thigh
evokes a reflex contraction of the muscle, the cremasteric reflex, which
is most pronounced in boys. It may represent a protective reflex. The
cremaster may also have a role in testicular thermoregulation since it is
activated by the cold.
Inguinal canal
The inguinal canal is a natural passageway between the muscle layers Intercrural fibres
Cutaneous
of the anterior abdominal wall in the region of the groin (Figs 61.13–
neurovascular Inguinal ligament
61.15; see Figs 76.15, 76.16). Its size and form vary with age, and
bundles
although it is present in both sexes, it is best developed in the male.
The canal is an oblique tunnel, with deep (internal) and superficial
(external) openings or rings. It transmits the spermatic cord in males, Superficial Cut edge of skin
the round ligament of the uterus in females, and the ilioinguinal nerve inguinal and superficial
in both sexes. ring fascia
Spermatic
Superficial inguinal ring cord
The superficial inguinal ring is a hiatus in the aponeurosis of external Femoral sheath
Superficial
oblique, just above and lateral to the crest of the pubis. The ring is
inguinal
actually triangular, with its apex pointing laterally towards the anterior lymph nodes Femoral branch
of genitofemoral
superior iliac spine. Although it varies in size, it does not usually extend
nerve
laterally beyond the medial third of the inguinal ligament. The ring is
Superficial
smaller in the female. The base of the triangular opening lies along the Long (great)
dorsal vein
crest of the pubis. Its sides are the lateral and medial crura of the of penis saphenous vein
opening in the aponeurosis. The lateral crus is stronger and is attached
to the pubic tubercle. The medial crus is thinner and its fibres attach to
the front of the pubic symphysis and interlace with those from the
opposite side. A few intercrural fibres arch above the apex of the super- Fig. 61.13 Superficial structures of the inguinal region and lower part of
ficial inguinal ring (see Fig. 61.13). Some fibres from the external the anterior abdominal wall on the left side. | 1,498 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Anterior AbdominAl wAll
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noitCeS
Aponeurosis of Inferior epigastric
transversus abdominis vessels
Cut edge of
Deep inguinal ring
Cut edge of rectus internal oblique
abdominis
Cremaster
Spermatic
cord
Internal oblique
Reflected part
of inguinal
Iliohypogastric
ligament
nerve
Anterior
Ilioinguinal nerve
superior
Dorsal nerve Femoral canal iliac spine
of penis Femoral vein
Dorsal artery Femoral artery
of penis
Deep dorsal
vein of penis Femoral branch Inguinal ligament
of genitofemoral
Superficial
dorsal vein nerve Iliacus
of penis Long saphenous
vein (tributary) Femoral nerve
Femoral artery
Femoral vein
Fig. 61.14 Dissection of the regions shown in Figure 61.13, with part of
external oblique removed. Psoas major
Femoral canal
Ischium
Pubis
Interfoveolar ligament
Pubic
Transversalis fascia
tubercle
Conjoint tendon
Internal oblique
Transversalis Fig. 61.16 Deep structures of the inguinal canal. The aponeurosis of
fascia external oblique has been removed. For clarity, the fibres of internal
Transversus oblique and rectus abdominis have been divided, and the structures
Spermatic
abdominis passing posteroinferiorly to the inguinal ligament have been excluded.
cord
Deep circumflex
Conjoint tendon
iliac artery,
Inguinal ascending branch
ligament, Inferior epigastric
reflected part vessels (running in boundaries
medial border of The inguinal canal slants obliquely downwards and medially, parallel
Dorsal nerve deep ring)
to and just above the medial part of the inguinal ligament. It extends
of penis
Femoral canal from the deep to the superficial inguinal rings; the length depends on
Dorsal artery the age of the individual, but in the adult is between 3 and 6 cm long.
Femoral vein
of penis The canal is bounded anteriorly by skin, superficial fascia and the
Femoral artery
aponeurosis of external oblique. In its lateral third, the anterior wall is
Deep dorsal
vein of penis reinforced by the muscular fibres of the internal oblique just above their
origin from the iliopectineal arch. Posteriorly lie the reflected inguinal
Spermatic Genitofemoral ligament, the conjoint tendon and the transversalis fascia, which sepa-
cord nerve, rate it from extraperitoneal connective tissue and peritoneum. Superi-
femoral branch
orly lie the arched fibres of internal oblique and transversus abdominis,
Superficial
dorsal vein forming the conjoint tendon medially. Inferiorly is the union of the
of penis transversalis fascia with the inguinal ligament and, at the medial end,
the lacunar ligament.
Fig. 61.15 Dissection of the inguinal region and lower part of the anterior In the newborn, the deep and superficial rings are nearly superim-
abdominal wall on the left side, with parts of external and internal oblique posed and the canal is extremely short. In infants undergoing inguinal
muscles removed. hernia repair, the canal is only about 1 cm long (Parnis et al 1997). As
a child grows, the anterior abdominal wall muscles develop further,
causing the positions of the rings to separate and the canal to lengthen.
oblique aponeurosis and its overlying fascia continue downwards from The canal becomes progressively more oblique so that, by adulthood,
the crura of the ring over the spermatic cord, and form the delicate it has separate anterior and posterior walls, creating a ‘shutter’ effect. At
external spermatic fascia; consequently, the ‘ring’ appears less of a dis- the superficial ring and medial end of the anterior wall, where the canal
crete opening in the living. is weakest, the posterior wall is strengthened by the conjoint tendon
and reflected inguinal ligament. Increases in intra-abdominal pressure
deep inguinal ring transmitted to the posterior wall of the canal are resisted by contraction
The deep inguinal ring is an opening in the transversalis fascia, approxi- of the three anterolateral abdominal wall muscles. The fibres of internal
mately midway between the anterior superior iliac spine and the pubic oblique and transversus abdominis, which form the conjoint tendon,
symphysis, and about 1 cm above the inguinal ligament (Hale et al are constantly active in standing; this activity increases during episodes
2010). It is oval, with a roughly vertical long axis. Its size varies between of increased intra-abdominal pressure.
individuals but it is usually 1–2 cm wide in adults and larger in the male.
It is related above to the arched lower margin of transversus abdominis relations
and medially to the interfoveolar ligament (see Fig. 61.16). The inferior The inferior epigastric vessels are important medial relations of the deep
epigastric vessels run in the medial border of the deep inguinal ring. inguinal ring (Fig. 61.16). They lie on the transversalis fascia as they
Traction on the fascial ring exerted by contraction of internal oblique ascend obliquely behind the conjoint tendon to enter the rectus sheath.
may narrow the opening when intra-abdominal pressure is increased. The inguinal triangle (of Hesselbach) is an important clinical landmark | 1,499 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Hernias of the anterior abdominal wall
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related to the posterior wall of the inguinal canal and is best appreciated Clinical features of inguinal hernias
by examining the inguinal canal region from within the abdomen
(see Fig. 61.3). The triangle is bounded inferiorly by the medial third
Indirect inguinal hernias often descend from lateral to medial, follow-
of the inguinal ligament, medially by the lower lateral border of rectus
ing the path of the inguinal canal, whereas direct inguinal hernias tend
abdominis, and laterally by the inferior epigastric vessels.
to protrude more directly anteriorly. With the hernia reduced, pressure
applied over the region of the deep inguinal ring may prevent the
lacunar ligament
appearance of an indirect hernia on standing or straining, but distin-
The lacunar ligament is a triangular band of fibrous tissue lying mainly
guishing an indirect from a direct inguinal hernia by clinical examina-
posterior to the medial end of the inguinal ligament. It measures
tion alone is not reliable (Ralphs et al 1980, Tromp et al 2014). Direct
approximately 2 cm from base to apex and is a little larger in the male.
hernias are more likely to have a wide neck, making strangulation less
It is formed from fibres of the medial end of the inguinal ligament
likely.
together with fibres from the fascia lata of the thigh, which join
the medial end of the inguinal ligament from below (Lytle 1974). The
inguinal fibres run posteriorly and laterally to the medial end of the
UMBILICAL HERNIA
pectineal line and are continuous with the pectineal fascia. They form
a near-horizontal, triangular sheet with a curved lateral border, which
forms the medial border of the femoral canal. The apex of the triangle The most extreme variety of umbilical hernia is known as an ompha-
is attached to the pubic tubercle. A strong fibrous band, the pectineal locele or exomphalos, a congenital malformation in which abdominal
ligament, extends laterally along the pectineal line from the pectineal viscera, covered by a membrane, protrude through a wide umbilical
attachment of the lacunar ligament (Faure et al 2001). defect (Fig. 61.17). The defect arises from a failure of closure of the
umbilical ring after return of the herniated midgut loop in the embryo.
Myofascial flaps and component separation The most common variety of umbilical hernia is caused by a weakness
of the umbilical scar tissue, and is often seen in babies, especially those
of African descent. The vast majority of these will close spontaneously
during early childhood. Most umbilical hernias in adults are acquired
Available with the Gray’s Anatomy e-book
as a result of stretching of the supporting umbilical fascia and are due
to obesity and chronically increased intra-abdominal pressure (e.g.
from multiple pregnancies or ascites).
HERNIAS OF THE ANTERIOR ABDOMINAL WALL
A wide range of anterior abdominal wall hernias are described. These FEMORAL HERNIA
include inguinal, umbilical, incisional, para-umbilical, femoral, and
rarer types such as Spigelian hernias (Larson and Farley 2002; Dabbas The femoral sheath is continuous with the transversalis fascia anteriorly
et al 2011). and the iliopsoas fascia posteriorly (p. 1338). The medial compartment
of the sheath is the femoral canal, which typically contains lymphatics
embedded in loose adipose connective tissue. The opening of the canal
INGUINAL HERNIA
is the femoral ring, bounded anteriorly by the inguinal ligament, pos-
teriorly by the pectineal ligament, medially by the crescentic lateral
Although the inguinal canal is arranged such that the weaknesses in the
margin of the lacunar ligament and laterally by the femoral vein. A
anterior abdominal wall caused by the deep and superficial inguinal
femoral hernia protrudes through the femoral ring, which is normally
rings are supported, the region is a common site of herniation, particu-
closed by a femoral septum of extraperitoneal tissue, and is therefore a
larly in males. An inguinal hernia involves the protrusion of a viscus
site of potential weakness. In females, the ring is relatively wider and
through the tissues of the inguinal region of the abdominal wall.
changes during pregnancy, which helps to explain why femoral hernias
Indirect inguinal hernia account for about 20% of all groin hernias in women but less than 1%
of groin hernias in men (Whalen et al 2011). The ring also widens with
advancing age. Variations in the attachment of the pectineal part of the
An indirect inguinal hernia arises through the deep inguinal ring lateral
lacunar ligament may also be a factor.
to the inferior epigastric vessels. Many indirect hernias are related to the
When a tongue of omentum or a loop of intestine bulges through
abnormal persistence of a patent processus vaginalis, a tube-like exten-
the ring, it pushes out a hernial sac of peritoneum that is covered by
sion of peritoneum through the inguinal canal that is present during
extraperitoneal tissue (the femoral septum) and descends within the
normal development and normally becomes occluded after birth
femoral canal to the saphenous opening. It is prevented from descend-
(p. 1215). Others are acquired as a result of progressive weakening of
ing further by the configuration of the femoral sheath and by the attach-
the posterior wall of the inguinal canal in the region of the deep
ment of fascia to the inferior rim of the saphenous opening. The hernial
inguinal ring. The hernia may pass through the deep ring or may expand
sac hence turns forwards, stretching the cribriform fascia and curving
the deep ring such that it is no longer a clear entity. Small indirect
upwards over the inguinal ligament within the subcutaneous tissues.
hernias lie below and lateral to the fibres of the conjoint tendon, but
While in the canal, the hernia is usually small because it is contained
larger hernias often distort and thin the tendon superiorly. Small indi-
by the surrounding tissues, but it enlarges as it expands into the subcu-
rect hernias that do not protrude beyond the inguinal canal are covered
taneous tissues.
by the same inner layers as the spermatic cord: namely, the internal
The small size of some femoral hernias explains why they can be
spermatic fascia and cremaster. If the hernia extends through the super-
easily missed on examination, particularly in the obese. They are also
ficial inguinal ring, it is also covered by external spermatic fascia. In much more prone to strangulation than inguinal hernias (Whalen et al
hernias related to a persistent fully patent processus vaginalis, the
2011). The site of strangulation varies: it may be at the neck of the
hernia contents may descend as far as the tunica vaginalis anterior to hernial sac, or at the saphenous opening, but is most often at the junc-
the testis. In many individuals with a partial or fully patent processus
tion of the falciform margin of the saphenous opening with the free
vaginalis, an indirect hernia will manifest in childhood, but in others,
edge of the pectineal part of the inguinal ligament. When the lacunar
an actual hernia into the potential sac may not develop until adult life,
ligament is being divided to release the neck of the hernia, care must
often as a consequence of increased intra-abdominal pressure or sudden
be taken to avoid or control an aberrant obturator artery (see above).
muscular strain.
The pubic tubercle can be a useful landmark when attempting to
distinguish an inguinal from a femoral hernia; a femoral hernia lies
Direct inguinal hernia below and lateral to this landmark, whilst an inguinal hernia is above.
However, clinical differentiation of groin hernias can be relatively unre-
A direct inguinal hernia arises medial to the inferior epigastric vessels. liable (Hair et al 2001), prompting the use of imaging in suspected
Direct hernias are always caused by an acquired weakness of the cases (Whalen et al 2011).
posterior wall of the inguinal canal (see Fig. 61.3B); as they enlarge,
they frequently extend through the anterior wall of the inguinal
canal or superficial inguinal ring, becoming covered by external sper- SPIGELIAN HERNIA
matic fascia in the process. A direct inguinal hernia may closely resem-
ble an indirect hernia and can be difficult to distinguish on clinical A Spigelian hernia is a protrusion of preperitoneal fat or a peritoneal
examination. sac through a congenital or acquired defect in the abdominal wall in | 1,500 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Anterior abdominal wall
1081.e1
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The goal of repairing massive ventral hernias lies in reapproximation
of the rectus sheath, thereby restoring anatomy and maximizing the
physiological potential of the abdominal wall. However, large fascial
defects often will not permit primary reapproximation without undue
tension. Many techniques have been developed that utilize the layered
nature of the abdominal wall musculature, allowing additional mobi-
lization of the fascial edges by ‘releasing’ incisions in myofascial layers
(Rosen 2011). This section reviews some of the more common tech-
niques. These repairs are often reinforced with synthetic or biopros-
thetic mesh applied in various ways: onlay (superficial to the fascia),
sublay (within the myofascial layers) or underlay (beneath the fascia
and exposed to intraperitoneal contents).
The Ramirez technique, originally described in 1990, refers to bilat-
eral release of the external oblique muscles, which can potentially
provide up to 10 cm, 20 cm and 8 cm of medial mobilization at the
upper, mid and lower abdomen, respectively (Ramirez et al 1990). A
disadvantage of this technique is that, in order to access and isolate the
external oblique muscles lateral to the linea semilunaris from a midline
incision, large subcutaneous flaps must be raised. This process neces-
A
sitates ligation of perforating vessels that supply the overlying subcuta-
neous tissue, rendering the flaps vulnerable to ischaemia, necrosis and
infection. In an attempt to overcome this limitation, an endoscopic
technique was developed to access the same myofascial layer through
smaller, lateral incisions. This technique obviates the need for large
subcutaneous flaps, a compromised blood supply, and the creation of
a large dead space for potential seroma formation. While reducing the
likelihood of wound necrosis and infection, the endoscopic technique
also reduces the maximum medial advancement by 1–2 cm on each
side. When release of the external oblique layer is insufficient, an addi-
tional 2–4 cm of fascial advancement can be gained by simultaneous
release of the posterior rectus sheath.
Often, the posterior rectus sheath can be incised independently of
external oblique release, allowing access to the retromuscular space and
providing several other options for medial advancement. The tradi-
tional Rives–Stoppa–Wantz technique, developed in the 1970s, involves
incising the posterior rectus sheath just lateral to the linea alba, allow-
ing a retromuscular dissection to the lateral edge of the rectus sheath.
If this does not gain sufficient medial advancement, further extension
can be obtained by release of transversus abdominis (Novitsky et al
2012). The posterior rectus sheath can be incised again 1–2 cm medial
to the linea semilunaris, safely preserving the laterally perforating neu-
rovascular bundles. This release exposes the underlying transversus
abdominis. Delicate transection of this muscle at its most medial inser-
tion allows access to a plane beneath transversus abdominis and super-
ficial to the transversalis fascia, preperitoneal fat and peritoneum. This
plane of dissection can be extended laterally to psoas major, inferiorly
to the space of Retzius, and superiorly beneath the diaphragm. The
same preperitoneal plane can be entered directly at the linea alba and
allows for lateral dissection, but does not provide the benefit of any
fascial advancement/release.
In addition to the medial mobilization of fascia aided by myofascial
flaps and component separations, these myofascial planes allow for
mesh reinforcement with extensive overlap without exposure to intra-
peritoneal contents (Heller et al 2012).
B
Fig. 61.17 A, A neonatal exomphalos. B, A persistent umbilical hernia in a
child. (A, B, Courtesy of Professor Mark Stringer.) | 1,501 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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the region of the intersection of the linea semilunaris with the arcuate 1995). There is currently little consensus among surgeons as to the
line (Skandalakis et al 2006, Larson and Farley 2002). Below this level, optimum method of repairing a large incisional hernia and numerous
the aponeuroses of external and internal oblique and transversus techniques are described (Cassar and Munro 2002). Needless to say, an
abdominis pass anterior to rectus abdominis and the posterior rectus understanding of abdominal wall anatomy is paramount to providing
sheath ends. A Spigelian hernia is an interstitial hernia in that the hernia a durable repair without compromising physiological function.
passes through a defect in the transversus and internal oblique aponeu-
roses but remains deep to the overlying external oblique aponeurosis.
Bonus e-book images and table
It is frequently associated with diagnostic delay.
INCISIONAL HERNIA Fig. 61.17 A, A neonatal exomphalos. B, A persistent umbilical
hernia in a child.
Incisional hernias now comprise as many as 20% of all anterior abdom-
inal wall hernias. This complication of abdominal laparotomy incisions Table 61.1 Distances of superior and deep inferior epigastric
is due to technical failures, wound infection, and patient-related factors arteries from midline.
such as obesity, medical comorbidities and old age (Carlson et al
KEY REFERENCES
Carlson MA, Ludwig KA, Condon RE 1995 Ventral hernia and other com- A description of the novel technique for posterior component separation,
plications of 1,000 midline incisions. South Med J 88:450–3. which was associated with a low perioperative morbidity and a low
A summary of the outcomes in 1079 consecutive clean or clean- recurrence rate. Overall, transversus abdominis release may be an important
contaminated midline abdominal incisions closed with running 0-loop nylon addition to the armamentarium of surgeons undertaking major abdominal
suture after both elective and emergency operations done between 1984 and wall reconstructions.
1991.
Ramirez OM, Ruas E, Dellon AL 1990 ‘Components separation’ method for
Cassar K, Munro A 2002 Surgical treatment of incisional hernia. Br J Surg closure of abdominal wall defects: an anatomic and clinical study. Plast
89:534–45. Reconstr Surg 86:519–26.
A review that compares the long-term recurrence rates of open primary Closure of large abdominal wall defects usually requires the transposition of
repair with open mesh and laparoscopic repair, citing the inadequacy of remote myocutaneous flaps or free-tissue transfers. The purpose of this study
open primary repair. was to determine if separation of the muscle components of the abdominal
wall would allow mobilization of each unit over a greater distance than is
El-Mrakby HH, Milner RH 2002 The vascular anatomy of the lower anterior
possible by mobilization of the entire abdominal wall as a block.
abdominal wall: a microdissection study on the deep inferior epigastric
vessels and the perforator branches. Plast Reconstr Surg 109:539–43; Rosen MJ 2011 Atlas of abdominal wall reconstruction. Philadelphia,
discussion 44–7. London: Saunders.
An account of how the deep inferior epigastric artery provides the main A text that summarizes the relevant anatomy of the abdominal wall,
blood supply to the lower abdominal wall. Microdissection of the artery, its relating this to techniques for abdominal wall reconstructions.
main branches and the perforator vessels was undertaken in 20 cadavers
Saber AA, Meslemani AM, Davis R et al 2004 Safety zones for anterior
and the findings summarized.
abdominal wall entry during laparoscopy: a CT scan mapping of
Heller L, McNichols CH, Ramirez OM 2012 Component separations. Semin epigastric vessels. Ann Surg 239:182–5.
Plast Surg 26:25–8. Trauma to abdominal wall blood vessels occurs in 0.2–2% of laparoscopic
A description of how, since its original description, the components procedures. Both superficial and deep abdominal wall vessels are at risk. The
separation technique underwent multiple modifications with the ultimate superficial vessels may be located by transillumination; however, the deep
goal of decreasing the morbidity associated with the traditional procedure. epigastric vessels cannot be effectively located by transillumination and, thus,
The extensive subcutaneous lateral dissection had been associated with other techniques should be used to minimize the risk of injury to these vessels.
ischaemia of the midline skin edges, wound dehiscence, infection and This study utilizes CT scans to map the pathway of the epigastric vessels.
seroma. Although the current trend is to proceed with minimally invasive
Skandalakis PN, Zoras O, Skandalakis JE et al 2006 Spigelian hernia: surgi-
component separation and to reinforce the fascia with mesh, the basic
cal anatomy, embryology, and technique of repair. Am Surg 72:42–8.
principles of the techniques, as described by Ramirez et al in 1990, have not
An account of Spigelian hernia (1–2% of all hernias), the protrusion of
changed over the years.
preperitoneal fat, peritoneal sac or organ(s) through a congenital or acquired
Larson DW, Farley DR 2002 Spigelian hernias: repair and outcome for 81 defect in the Spigelian aponeurosis (i.e. the aponeurosis of the transverse
patients. World J Surg 26:1277–81. abdominal muscle limited by the linea semilunaris laterally and the lateral
An account of Spigelian hernia, a rare partial abdominal wall defect. The edge of the rectus muscle medially). Mostly, these hernias lie in the ‘Spigelian
frequent lack of physical findings, along with vague associated abdominal hernia belt’, a transverse 6 cm-wide zone above the interspinal plane; lower
complaints, makes the diagnosis elusive. A retrospective review of Mayo hernias are rare and should be differentiated from direct inguinal or
Clinic patients was performed to find all patients who had undergone supravescical hernias. Although named after Adriaan van der Spieghel, the
surgical repair of a Spigelian hernia from 1976 to 1997. semilunar line (linea Spigeli) was only described by Spieghel in 1645. Josef
Klinkosch first defined the Spigelian hernia as a defect in the semilunar line
Novitsky YW, Elliott HL, Orenstein SB et al 2012 Transversus abdominis
in 1764. Defects in the aponeurosis of transverse abdominal muscle (mainly
muscle release: a novel approach to posterior component separation
under the arcuate line and more often in obese individuals) have been
during complex abdominal wall reconstruction. Am J Surg 204:
considered as the principal aetiological factor.
709–16. | 1,502 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Anterior abdominal wall
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Acland RD 2008 The inguinal ligament and its lateral attachments: correct- Naraynsingh V, Maharaj R, Dan D et al 2012 Strong linea alba: myth or
ing an anatomical error. Clin Anat 21:55–61. reality? Med Hypotheses 78:291–2.
Akram J, Matzen SH 2014 Rectus abdominis diastasis. J Plast Surg Hand Surg Norton-Old KJ, Schache AG, Barker PJ et al 2013 Anatomical and mechani-
48:163–9. cal relationship between the proximal attachment of adductor longus
Carlson MA, Ludwig KA, Condon RE 1995 Ventral hernia and other com- and the distal rectus sheath. Clin Anat 26:522–30.
plications of 1,000 midline incisions. South Med J 88:450–3. Novitsky YW, Elliott HL, Orenstein SB et al 2012 Transversus abdominis
A summary of the outcomes in 1079 consecutive clean or clean- muscle release: a novel approach to posterior component separation
contaminated midline abdominal incisions closed with running 0-loop nylon during complex abdominal wall reconstruction. Am J Surg 204:
suture after both elective and emergency operations done between 1984 and 709–16.
1991. A description of the novel technique for posterior component separation,
which was associated with a low perioperative morbidity and a low
Cassar K, Munro A 2002 Surgical treatment of incisional hernia. Br J Surg
recurrence rate. Overall, transversus abdominis release may be an important
89:534–45.
addition to the armamentarium of surgeons undertaking major abdominal
A review that compares the long-term recurrence rates of open primary
wall reconstructions.
repair with open mesh and laparoscopic repair, citing the inadequacy of
open primary repair. Pai MM, Krishnamurthy A, Prabhu LV et al 2009 Variability in the origin of
the obturator artery. Clinics (Sao Paulo) 64:897–901.
Chopra J, Rani A, Rani A et al 2011 Re-evaluation of superficial fascia of
anterior abdominal wall: a computed tomographic study. Surg Radiol Parnis SJ, Roberts JP, Hutson JM 1997 Anatomical landmarks of the inguinal
Anat 33:843–9. canal in prepubescent children. Aust N Z J Surg 67:335–7.
Dabbas N, Adams K, Pearson K et al 2011 Frequency of abdominal wall Ralphs DN, Brain AJ, Grundy DJ et al 1980 How accurately can direct and
hernias: is classical teaching out of date? JRSM Short Rep 2:5. indirect inguinal hernias be distinguished? Br Med J 280:1039–40.
El-Mrakby HH, Milner RH 2002 The vascular anatomy of the lower anterior Ramirez OM, Ruas E, Dellon AL 1990 ‘Components separation’ method for
abdominal wall: a microdissection study on the deep inferior epigastric closure of abdominal wall defects: an anatomic and clinical study. Plast
vessels and the perforator branches. Plast Reconstr Surg 109:539–43; Reconstr Surg 86:519–26.
discussion 44–7. Closure of large abdominal wall defects usually requires the transposition of
An account of how the deep inferior epigastric artery provides the main remote myocutaneous flaps or free-tissue transfers. The purpose of this study
blood supply to the lower abdominal wall. Microdissection of the artery, its was to determine if separation of the muscle components of the abdominal
main branches and the perforator vessels was undertaken in 20 cadavers wall would allow mobilization of each unit over a greater distance than is
and the findings summarized. possible by mobilization of the entire abdominal wall as a block.
Fathi AH, Soltanian H, Saber AA 2012 Surgical anatomy and morphologic Rath AM, Attali P, Dumas JL et al 1996 The abdominal linea alba: an
variations of umbilical structures. Am Surg 78:540–4. anatomo-radiologic and biomechanical study. Surg Radiol Anat 18:
281–8.
Faure JP, Hauet T, Scepi M et al 2001 The pectineal ligament: anatomical
study and surgical applications. Surg Radiol Anat 23:237–42 Rizk NN 1980 A new description of the anterior abdominal wall in man
and mammals. J Anat 131:373–85.
Hair A, Paterson C, O’Dwyer PJ 2001 Diagnosis of a femoral hernia in the
elective setting. J R Coll Surg Edinb 46:117–18. Rosen MJ 2011 Atlas of abdominal wall reconstruction. Philadelphia,
London: Saunders.
Hale SJ, Mirjalili SA, Stringer MD 2010 Inconsistencies in surface anatomy:
A text that summarizes the relevant anatomy of the abdominal wall,
the need for an evidence-based reappraisal. Clin Anat 23:922–30.
relating this to techniques for abdominal wall reconstructions.
Heller L, McNichols CH, Ramirez OM 2012 Component separations. Semin
Plast Surg 26:25–8. Rozen WM, Ashton MW, Taylor GI 2008 Reviewing the vascular supply of
A description of how, since its original description, the components the anterior abdominal wall: redefining anatomy for increasingly refined
separation technique underwent multiple modifications with the ultimate surgery. Clin Anat 21:89–98.
goal of decreasing the morbidity associated with the traditional procedure. Rozen WM, Pan WR, Le Roux CM et al 2009 The venous anatomy of the
The extensive subcutaneous lateral dissection had been associated with anterior abdominal wall: an anatomical and clinical study. Plast Recon-
ischaemia of the midline skin edges, wound dehiscence, infection and str Surg 124:848–53.
seroma. Although the current trend is to proceed with minimally invasive Saber AA, Meslemani AM, Davis R et al 2004 Safety zones for anterior
component separation and to reinforce the fascia with mesh, the basic abdominal wall entry during laparoscopy: a CT scan mapping of
principles of the techniques, as described by Ramirez et al in 1990, have not epigastric vessels. Ann Surg 239:182–5.
changed over the years. Trauma to abdominal wall blood vessels occurs in 0.2–2% of laparoscopic
Kayalioglu G, Altay B, Uyaroglu FG et al 2008 Morphology and innervation procedures. Both superficial and deep abdominal wall vessels are at risk. The
of the human cremaster muscle in relation to its function. Anat Rec superficial vessels may be located by transillumination; however, the deep
(Hoboken) 291:790–6. epigastric vessels cannot be effectively located by transillumination and, thus,
other techniques should be used to minimize the risk of injury to these vessels.
Korenkov M, Beckers A, Koebke J et al 2001 Biomechanical and morphologi-
This study utilizes CT scans to map the pathway of the epigastric vessels.
cal types of the linea alba and its possible role in the pathogenesis of
midline incisional hernia. Eur J Surg 167:909–14. Schlenz I, Burggasser G, Kuzbari R et al 1999 External oblique abdominal
Lancerotto L, Stecco C, Macchi V et al 2011 Layers of the abdominal wall: muscle: a new look on its blood supply and innervation. Anat Rec
anatomical investigation of subcutaneous tissue and superficial fascia. 255:388–95.
Surg Radiol Anat 33:835–42. Shafik A 1977 The cremasteric muscle. In: Johnson AD, Gomes WR (eds)
Larson DW, Farley DR 2002 Spigelian hernias: repair and outcome for 81 The Testis. Academic Press: New York.
patients. World J Surg 26:1277–81. Skandalakis PN, Zoras O, Skandalakis JE et al 2006 Spigelian hernia: surgi-
An account of Spigelian hernia, a rare partial abdominal wall defect. The cal anatomy, embryology, and technique of repair. Am Surg 72:42–8.
frequent lack of physical findings, along with vague associated abdominal An account of Spigelian hernia (1–2% of all hernias), the protrusion of
complaints, makes the diagnosis elusive. A retrospective review of Mayo preperitoneal fat, peritoneal sac or organ(s) through a congenital or
Clinic patients was performed to find all patients who had undergone acquired defect in the Spigelian aponeurosis (i.e. the aponeurosis of the
surgical repair of a Spigelian hernia from 1976 to 1997. transverse abdominal muscle limited by the linea semilunaris laterally and
the lateral edge of the rectus muscle medially). Mostly, these hernias lie in
Lee MW, McPhee RW, Stringer MD 2008 An evidence-based approach to
the ‘Spigelian hernia belt’, a transverse 6 cm-wide zone above the
human dermatomes. Clin Anat 21:363–73.
interspinal plane; lower hernias are rare and should be differentiated from
Loukas M, Myers C, Shah R et al 2008 Arcuate line of the rectus sheath: direct inguinal or supravescical hernias. Although named after Adriaan van
clinical approach. Anat Sci Int 83:140–4. der Spieghel, the semilunar line (linea Spigeli) was only described by
Lytle WJ 1974 The inguinal and lacunar ligaments. J Anat 118:241–51. Spieghel in 1645. Josef Klinkosch first defined the Spigelian hernia as a
defect in the semilunar line in 1764. Defects in the aponeurosis of
Lytle WJ 1979 Inguinal anatomy. J Anat 128:581–94.
transverse abdominal muscle (mainly under the arcuate line and more often
Markman B, Barton FE 1987 Anatomy of the subcutaneous tissue of the in obese individuals) have been considered as the principal aetiological
trunk and lower extremity. Plast Reconstr Surg 80:248–54. factor. | 1,503 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Teoh LS, Hingston G, Al-Ali S et al 1999 The iliopubic tract: an important Tubbs RS, McDaniel JG, Burns AM et al 2009 Anatomy of the reflected liga-
anatomical landmark in surgery. J Anat 194:137–41. ment of the inguinal region. Rom J Morphol Embryol 50:689–91.
Tokita K 2006 Anatomical significance of the nerve to the pyramidalis Whalen HR, Kidd GA, O’Dwyer PJ 2011 Femoral hernias. BMJ 343:d7668.
muscle: a morphological study. Anat Sci Int 81:210–24. Yang D, Morris SF, Geddes CR et al 2003 Neurovascular territories of the
Tourani SS, Taylor GI, Ashton MW 2013 Anatomy of the superficial lymphat- external and internal oblique muscles. Plast Reconstr Surg 112:
ics of the abdominal wall and the upper thigh and its implications in 1591–5.
lymphatic microsurgery. J Plast Reconstr Aesthet Surg 66:1390–5.
Tromp WG, van den Heuvel B, Dwars BJ 2014 A new accurate method of
physical examination for differentiation of inguinal hernia types. Surg
Endosc 28:1460–4. | 1,504 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Posterior abdominal wall and CHAPTER
62
retroperitoneum
THORACOLUMBAR FASCIA
DEFINITIONS, BOUNDARIES AND CONTENTS
The thoracolumbar fascia is composed of a complex arrangement of
The posterior abdominal wall does not have an agreed uniform defini- multiple fascial layers that is most prominent at the caudal end of the
tion. It represents the posterior boundary of the abdominal cavity. In lumbar spine (Ch. 43) (Willard et al 2012). In the lumbar region, it is
common with the anterior and lateral abdominal walls, it is composed often described as having three layers (Figs 62.1–62.3, see Fig. 43.6). The
of several layers (skin, superficial fascia, muscle, extraperitoneal fat/ posterior layer is attached medially to the spines of the lumbar vertebrae
fascia and parietal peritoneum). The vertebral column and paraverte- and to the supraspinous ligament; it has a superficial lamina (the
bral muscles of the back are part of the posterior abdominal wall, but aponeurosis of latissimus dorsi) and a deep lamina that covers the pos-
are usually not considered in this context. The posterior abdominal wall terior surface of the paraspinal muscles. The middle layer is attached
is continuous with the posterior thoracic wall at the posterior attach- medially to the tips of the transverse processes of the lumbar vertebrae
ment of the diaphragm, with the posterior wall of the pelvis inferiorly, and extends laterally behind quadratus lumborum; inferiorly, it attaches
and with the anterolateral abdominal wall laterally. to the iliac crest, and superiorly to the lower border of the twelfth rib.
The retroperitoneum is a three-dimensional compartment bounded The anterior layer covers the anterior surface of quadratus lumborum
anteriorly by the parietal peritoneum of the posterior abdominal wall and is attached medially to the transverse processes of the lumbar verte-
and superiorly by the diaphragm. Inferiorly and laterally, it is continu- brae behind psoas major. Laterally, it fuses with the transversalis fascia
ous with the extraperitoneal connective tissues lining the pelvis and and the aponeurosis of transversus abdominis. Inferiorly, it is attached
anterolateral abdominal wall, respectively. The posterior boundary of to the iliolumbar ligament and adjoining iliac crest. Superiorly, it is
the retroperitoneum is variably defined, depending on whether the attached to the inferior border of the twelfth rib and extends to the
psoas muscles and quadratus lumborum are regarded as contents or transverse process of the first lumbar vertebra, forming the lateral arcuate
boundaries of this compartment. ligament of the diaphragm. The posterior and middle layers of the tho-
The posterior abdominal wall and the retroperitoneum are related racolumbar fascia fuse at the lateral margin of the paraspinal muscles
but different concepts. The retroperitoneum is a compartment and a (the so-called ‘lateral raphe’), thereby enclosing the paraspinal muscles
three-dimensional space, a concept invoked when localization, spread in an osteofascial compartment. Although contained in layers of thora-
and containment of disease are primary considerations. The posterior columbar fascia, the paraspinal muscles are conceptualized as part of ‘the
abdominal wall is a part of the parietal coverings of abdominal viscera, back’. The aponeurosis of transversus abdominis fuses with both the
a concept invoked when considering posteriorly directed surgery from anterior layer of thoracolumbar fascia at the lateral margin of quadratus
within the abdomen, posterolateral access to retroperitoneal organs lumborum and with the lateral raphe behind quadratus lumborum.
(e.g. nephrectomy or percutaneous endoscopic renal access), or else in
contradistinction to the anterior abdominal wall. Advances in cross-
sectional imaging have promoted a better understanding of the anatomy ILIOPSOAS FASCIA
of the retroperitoneum, particularly its compartmental anatomy, and
with it the retroperitoneum has become the more prevalent clinical Psoas fascia
concept outside of specific surgical circumstances.
The retroperitoneum houses the paired viscera originating from the A relatively dense layer of fascia covers the anterior surface of psoas
embryonic extracoelomic space: the kidneys and ureters (Ch. 74), and major. Medially, it is continuous with the attachments of the muscle to
the suprarenal glands (Ch. 71) and their vessels and nerves. It also the transverse processes and bodies of the lumbar vertebrae and the
houses the unpaired derivatives of the embryonic intracoelomic gut tendinous arches. Laterally, the fascia blends with the fascia over quad-
tube secondarily retroperitonealized: the duodenum (Ch. 65), the pan- ratus lumborum above and is continuous with the iliac fascia below.
creas (Ch. 69), and the ascending and descending colon (Ch. 66) and Superiorly, the fascia merges with the medial arcuate ligament, while,
their vessels and nerves. inferiorly, it extends down into the thigh around the iliopsoas tendon.
Attached to the retroperitoneum are the mesenteries of the small The psoas fascia separates the anterior surface of the muscle and the
bowel (Ch. 65), transverse and sigmoid colons (Ch. 66), and the peri- lumbar plexus within it from the retroperitoneal structures lying ante-
toneal ligaments of the liver (Ch. 67) and spleen (Ch. 70). riorly. A psoas abscess, which can arise by haematogenous seeding or
The retroperitoneum contains the abdominal aorta and branches; from direct extension of infection from adjacent structures (e.g. the
the inferior vena cava and tributaries; the origins of the azygos and spine, kidneys or colon), often tracks along the muscle within the fascia,
hemiazygos veins; the pre- and para-aortic (lumbar) lymph nodes, and, rarely, may ‘point’ in the groin.
cisterna chyli and the origin of the thoracic duct (Ch. 56); the diaphrag-
matic crura (Ch. 55); the lumbar plexus and lumbosacral trunk; and Iliac fascia
the autonomic plexuses of the abdomen (Ch. 59).
The iliac fascia overlies iliacus. Superiorly and laterally, it is attached to
the inner aspect of the iliac crest, and medially it blends with the ante-
SKIN AND SOFT TISSUES
rior layer of thoracolumbar fascia over quadratus lumborum and with
the psoas fascia. Inferiorly and laterally, it continues into the thigh to
The skin of the posterior abdominal wall is supplied by musculocutane- fuse with the femoral sheath, while medially, it is attached to the peri-
ous branches of the lumbar arteries and veins, and innervated by the osteum of the ilium and iliopubic eminence at the pelvic brim. Both
dorsal rami of the lower thoracic and lumbar spinal nerves. However, the femoral nerve and lateral femoral cutaneous nerve lie under the iliac
the cutaneous distribution of the dorsal rami of L4 and L5 is variable fascia in the pelvis, where they can be targeted for image-guided nerve
and controversial (Lee et al 2008). blocks (Hebbard et al 2011).
In the muscular posterior abdominal wall, intermuscular fascial
layers delineate compartments and provide the conceptual anatomical
framework. In the retroperitoneum, the compartments (the clinical VISCERAL FASCIAE
synonym is ‘spaces’) and their interrelationships provide the conceptual
framework, particularly in cross-sectional anatomy, with the dividing The organization of the retroperitoneum is most easily conceptualized
fasciae often hard to visualize unless outlined by disease processes. in terms of compartments (synonym: spaces) rather than fasciae (Dodds 1083 | 1,505 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Posterior abdominal wall and retroPeritoneum
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noitCes
Anterior perirenal fascia fused with posterior peripancreatic fascia
Posterior parietal peritoneum
Retromesocolic fascia (of Toldt) fused with anterior peripancreatic fascia
Ascending (fourth) part of duodenum
Anterior leaf of descending mesocolon
Root of transverse mesocolon
Descending mesocolon
Peritoneal cavity
Middle colic vessels fenestrating the
anterior peripancreatic fascia Descending colon
Anterior perirenal fascia (fused with retrocolic/mesocolic fascia)
Body of pancreas
Paracolic gutter
Splenic vein Lateral abdominal parietal peritoneum
Peripancreatic space
Extraperitoneal fat
Abdominal aorta
Kidney
Transversus abdominis
Renal vessels
Crus of diaphragm
Internal oblique
Body of L1 vertebra
External oblique
Psoas major
Psoas fascia Lateroconal fascia
Left (descending) pericolic space
Erector spinae Posterior perirenal fascia
Perirenal space
Aponeurosis of latissimus dorsi (superficial lamina of posterior layer of thoracolumbar fascia)
Posterior pararenal space
Thoracolumbar fascia
Latissimus dorsi
Middle layer of
thoracolumbar fascia Fascia over quadratus lumborum
Deep lamina of posterior layer of thoracolumbar fascia Quadratus lumborum
Lateral raphe
Anterior layer of thoracolumbar fascia
Fig. 62.1 Compartments and fasciae of the upper retroperitoneum (left side). A transverse section at approximately the level of the first lumbar vertebra,
showing the location and relations of the peripancreatic space.
Anterior perirenal Peritoneum
fascia fused with Descending Internal oblique
Kidney Descending retrocolic/mesocolic fascia Gonadal vessels colon External
colon Transversus oblique
Ureter Retroperitoneal 'space'
Left colic artery Peritoneum abdominis
Psoas
Ureter
major Transversus
Branches of abdominis Anterior and posterior
layers of the lower
lumbar plexus
extension of the
perirenal fascia
Common Retrocolic/
iliac vessel mesocolic
fascia
Obturator
nerve Lateral femoral
cutaneous nerve
Psoas
major
External
oblique
Iliac fascia
Internal
oblique L5 vertebra Psoas fascia
Lateroconal Ilium
fascia
Iliacus
Thoracolumbar Posterior
fascia Femoral nerve
perirenal Body of
L3 vertebra Latissimus fascia Genitofemoral nerve
dorsi
Deep muscles
of the back Fascia over Fig. 62.3 Compartments and fasciae of the lower retroperitoneum (left
Psoas fascia quadratus lumborum side). A transverse section at approximately the L4 vertebral level,
showing the location and relations of the pericolic space.
Quadratus Ilioinguinal
lumborum nerve
Fig. 62.2 Compartments and fasciae of the mid-retroperitoneum (left eponym for different fasciae; different eponyms have been used to refer
side). A transverse section at approximately the level of the third lumbar to the same fascia. Thus, ‘Gerota’s fascia’ has been used to refer to the
vertebra, showing the location and relations of the perirenal space. entire perirenal fascia or to its anterior or posterior layers (Chesbrough
et al 1989). ‘Toldt’s fascia’ has been used to refer to the fusion fascia
et al 1986). The fasciae bounding the compartments limit or direct the behind the ascending or descending colon (Culligan et al 2013), or to
spread of blood, fluid, gas or malignant disease, but are variable and the posterior perirenal fascia, or to the fusion fascia behind the tail of
often difficult to see with cross-sectional imaging. the pancreas (Kimura et al 2010). ‘Zuckerkandl’s fascia’ has been used
The fascial layers located between the posterior parietal peritoneum to refer to the posterior or anterior perirenal fascia (Chesbrough et al
and the quadratus lumborum have been described in confusing epony- 1989). ‘Treitz’s fascia’ has been used to refer to the fusion fascia behind
mous terms in the literature. Different authors have used the same the head of the pancreas (Kimura et al 2010). | 1,506 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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The concept of ‘fusion fascia’ describes a retroperitoneal fascia medially with the mesocolon (see Figs 62.1–62.3). The pericolic spaces
formed by the fusion of an embryonic mesentery with embryonic retro- contain a variable amount of fat and are limited anteriorly, superiorly
peritoneum. It is an avascular layer that allows a dissection plane to be and laterally by the colonic serosa. Inferiorly, the pericolic spaces are
developed, and also limits the spread of disease. The retropancreati- continuous with the retroperitoneal spaces of the iliac fossae. Posteri-
coduodenal fascia and the retrocolic/retromesocolic fascia (right and orly, each pericolic space is limited by a fusion fascia formed by the
left) are fusion fascias, and delimit their respective compartments. They right leaf of the embryonic mesocolon fusing to the left leaf of the
were first described in detail by the Austrian anatomist Carl Toldt, and embryonic duodenal mesentery and embryonic retroperitoneum further
only later reported in the English literature (Congdon et al 1942). laterally. This retrocolic fascia (of Toldt) (Culligan et al 2013, Culligan
Traditional compartmental anatomy of the retroperitoneum divides et al 2014) forms the classic bloodless plane of dissection when per-
it into the anterior and posterior pararenal spaces, and the perirenal forming a hemicolectomy. Its plane is entered by incising the junction
space. ‘Anterior pararenal space’ describes the compartment between of the colonic serosa with the parietal peritoneum at the white line (of
the posterior peritoneum and the anterior perirenal fascia. This is an Toldt) in the paracolic gutter. Radiologically, the retrocolic fascia may
oversimplification and is unable to explain all patterns of disease con- be indistinguishable from the anterior perirenal fascia when lateral to
tainment or spread. The smallest set of compartments sufficient to the duodenum and pancreas.
explain most such phenomena is as follows. Variation in colonic retroperitonealization may produce a free
mesocolic pedicle instead (most commonly seen at the caecum).
Perirenal space
Lateroconal fascia
Lateroconal fascia was originally defined as the fascial layer extending
The paired perirenal space is bounded by the perirenal fascia, which
from the junction of the anterior and posterior perirenal fasciae to
envelops the kidney and suprarenal gland on each side. Perirenal fascia
the parietal peritoneum in the lateral paracolic gutter (Congdon and
is traditionally described as having anterior and posterior layers, which
Edson 1941). It is better understood as the lateral extension of the
are continuous with each other laterally (see Figs 62.1–62.3; Ch. 74).
retrocolic fusion fascia that blends with the parietal peritoneum (see
The perirenal fascia can usually be identified on cross-sectional imaging
Figs 62.1–62.3).
as a thin layer surrounding the kidney and suprarenal gland, separated
The various compartments described above are illustrated in the
from the renal capsule by a variable amount of perirenal fat. Inferiorly,
context of clinical disease in Figures 62.4–62.6.
the perirenal space continues down around the ureter but becomes
progressively narrower and may or may not extend into the pelvic ret-
roperitoneum. Medially, the two perirenal spaces may interconnect
BONES
anterior to the aorta and inferior vena cava (Kneeland et al 1987). The
existence of a fascial partition separating the kidney and ipsilateral
suprarenal gland within the perirenal fascial envelope is controversial The posterior abdominal wall is supported by the vertebral column and
(Amin et al 1976). bony pelvis. The individual bones are the lower two ribs, the twelfth
thoracic and five lumbar vertebrae, and the sacrum and ilium, together
Anterior and posterior pararenal spaces with their interconnecting ligaments (Chs 43, 53).
The anterior pararenal space (an oversimplification) refers to the region
MUSCLES
between the anterior layer of perirenal fascia and the posterior parietal
peritoneum; it is not a single compartment. On the right, it contains
the second part of the duodenum, ascending colon and its mesentery, The majority of the muscles of the posterior abdominal wall are func-
and on the left, the fourth part of the duodenum, descending colon tionally part of the lower limb or vertebral column. They provide the
and its mesentery (see Figs 62.1–62.3). surface against which the neurovascular and visceral structures of the
The potential compartment between the posterior layer of perirenal retroperitoneum lie (Fig. 62.7; see Fig. 62.14).
fascia and the thoracolumbar and psoas fasciae on each side is the
Quadratus lumborum
posterior pararenal space. It contains a variable amount of fat. Laterally,
it is continuous with the extraperitoneal (properitoneal) fat of the Quadratus lumborum is an irregularly shaped quadrilateral muscle,
anterolateral abdominal wall, and inferiorly, with the retroperitoneal broader at its inferior attachment than superiorly.
fat overlying iliacus and the pelvic wall, and the perivesical fat (Coffin
et al 2015). Attachments The inferior attachment is by aponeurotic fibres to the
When the ascending or descending colon is retrorenal (an anatomi- iliac crest over an area 5–7 cm lateral to the tip of the L4 transverse
cal variant), the colon and pericolic space lie in a groove between the process and/or the iliolumbar ligament. The superior attachment is to
posterior layer of perirenal fascia and the posterior pararenal space. the lower anterior surface of the twelfth rib, the lateral surface of the
twelfth thoracic vertebra, and the apices of the transverse processes of
Peripancreatic space the upper four lumbar vertebrae. Fascicles vary in number and size but
are arranged in three layers: anterior, middle and posterior (Phillips
et al 2008).
The peripancreatic space contains the duodenum and pancreas along
with the origins of the superior mesenteric vessels and the retroperito-
Relations Anteriorly are the colon (ascending on the right, descend-
neal segments of the common bile duct, portal vein and hepatic artery.
ing on the left), kidney, psoas major and minor, and diaphragm. The
The posterior boundary is a fusion fascia formed by fusion of the
subcostal, iliohypogastric and ilioinguinal nerves lie on the fascia ante-
embryonic duodenal mesentery to the embryonic retroperitoneum
rior to the muscle, bound down to it by the medial continuation of the
(Dodds et al 1986). This fascia is termed ‘retropancreatic’ or ‘retropan-
transversalis fascia.
creaticoduodenal’ fascia in the imaging literature, and ‘fusion fascia of
Treitz’ in the surgical literature (Kimura et al 2010). The fascia forms a
Vascular supply Quadratus lumborum is supplied by branches of
relatively bloodless dissection plane, used to mobilize the duodenum
the lumbar arteries, the arteria lumbales imae from the median sacral
and head of the pancreas.
artery, the lumbar branch of the iliolumbar artery, and branches of the
The lateral extent of the peripancreatic space is variable; it lies pos-
subcostal artery.
terior to the ascending and descending colon and anterior to the peri-
renal space (see Fig. 62.1). At the tail of the pancreas, the peripancreatic
Innervation The muscle is innervated by the ventral rami of the
space lies in continuity with the splenorenal ligament. Anteriorly, it is
twelfth thoracic and upper three or four lumbar spinal nerves.
in continuity with the transverse mesocolon and small bowel mesen-
tery. Consequently, peripancreatic fluid collections may extend into
Actions Quadratus lumborum fixes the twelfth rib, and acts as a
both mesenteries and extend posterior to the ascending and descending
muscle of inspiration by helping to stabilize the lower attachments of
colon but do not usually cross into the perirenal and pericolic spaces.
the diaphragm. With the pelvis fixed, unilateral contraction flexes the
vertebral column to the same side, and bilateral contraction probably
Pericolic spaces
helps to extend the lumbar part of the vertebral column. These actions
on the lumbar spine are reported to be weak (Phillips et al 2008) and
The ascending and descending pericolic spaces are narrow compart- yet the muscle undergoes considerable hypertrophy in some sporting
ments surrounding the respective parts of the colon and in continuity activities (Ranson et al 2008). | 1,507 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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18
9
7 2 10
8
10
6
19 3 17 4 5 6 7
4
1 5 2 1
20 8 4 12 3 14
10 9 11 4 23 26 25 13
21 11 19 23
14 16 20 27 24 15
22 22
15 12 13 16 18
23 21 29 28 17
24
A B
3 9
9
8
7
4
3
2 5
2
10 1
4
7
5
1 5
6
8
7 5
7
14
11
6
12
13
C D
Fig. 62.4 A 58-year-old male with chronic pancreatitis and a peripancreatic pseudocyst. Oral and intravenous contrast-enhanced computed tomography
(CT; axial and sagittal planes). The pseudocyst, containing gas and fluid, has expanded the peripancreatic space. The fusion fasciae forming the
boundaries of the peripancreatic space are thickened through chronic inflammation and are easily visible. A, A transverse section at the level of the body
of the second lumbar vertebra. Key: 1, neck of pancreas; 2, gas in anterior part of collection (outlining peripancreatic space); 3, fluid and debris in
posterior (dependent) part of collection (outlining peripancreatic space); 4, retropancreatic fusion fascia (anterior perirenal fascia fused to right leaf of
mesoduodenum); 5, anterior peripancreatic fascia fused to right leaf of left mesocolon; 6, anterior peripancreatic fascia deep to left mesocolon and
collapsed lesser sac; 7, anterior peripancreatic fascia fused to peritoneum of lesser sac in gastric bed; 8, superior mesenteric artery; 9, abdominal aorta;
10, inferior vena cava; 11, left renal vein; 12, left kidney parenchyma; 13, left perirenal space (not distinguishable from left posterior pararenal space);
14, right kidney parenchyma; 15, right perirenal space (not distinguishable from right posterior pararenal space); 16, upper L2 vertebral body; 17, splenic
flexure; 18, stomach (elevated and compressed by collection); 19, gallbladder; 20, right lobe of liver (segments 5 and 6); 21, right crus of diaphragm;
22, origin of left psoas major; 23, left quadratus lumborum; 24, left erector spinae group. B, A transverse section at the level of the body of the fourth
lumbar vertebra. Key: 1, inferior part of body and uncinate process of pancreas; 2, distal second part of duodenum; 3, third part of duodenum; 4,
peripancreatic space collection (around and anterior to pancreas and duodenum); 5, superior mesenteric vein; 6, superior mesenteric artery; 7, small
bowel mesentery; 8, part of collection dissecting into transverse mesocolon; 9, transverse mesocolon (fused to greater omentum); 10, transverse colon;
11, collection dissecting behind ascending colon; 12, ascending colon; 13, collection (with gas) dissecting behind descending colon; 14, descending
colon; 15, left kidney parenchyma; 16, left perirenal space; 17, left posterior perirenal fascia (normal thickness, therefore faint); 18, left posterior pararenal
space; 19, right kidney parenchyma; 20, right perirenal space; 21, right posterior perirenal fascia; 22, right posterior pararenal space; 23, anterior
pararenal fascia (thickened through chronic inflammation); 24, upper L4 vertebral body; 25, abdominal aorta; 26, inferior vena cava; 27, right psoas
major; 28, left quadratus lumborum; 29, left erector spinae group. C, A mid-sagittal section. Key: 1, neck of pancreas; 2, gas in anterior part of
collection; 3, fluid in posterior part of collection; 4, coeliac trunk; 5, superior mesenteric artery; 6, left renal vein; 7, abdominal aorta; 8, diaphragmatic
crura; 9, left lobe of liver; 10, antrum of stomach (collapsed); 11, part of collection dissecting into transverse mesocolon; 12, transverse colon; 13, part
of collection dissecting into small bowel mesentery; 14, third part of duodenum. D, A left sagittal section through left renal hilum. Key: 1, body of
pancreas; 2, fluid collection; 3, fundus of stomach (containing oral contrast); 4, body of stomach (containing oral contrast and displaced); 5, left anterior
perirenal fascia fused with retropancreatic fascia; 6, left anterior perirenal fascia fused with right leaf of left mesocolon (fusion fascia of Toldt); 7, fourth
part of duodenum; 8, left kidney parenchyma; 9, spleen. | 1,508 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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5
11
6
10 15
7
9
8
4
12
3
1 2
4 19
1 11
3 3 3 10 14
2 13
3 6 15
5
6 12 17 16
9
18
7 13
8
14
A B
Fig. 62.5 A 43-year-old male with subacute retrocaecal appendicitis. Inflammatory fluid and stranding in the right pericolic space. The fused right
anterior perirenal fascia and right mesocolon (the fusion fascia of Toldt) is visible. A, A transverse section through the vermiform appendix. Key: 1,
thickened and inflamed retrocaecal appendix; 2, inflammatory fluid tracking posteriorly in right pericolic space, anterior to right perirenal space; 3,
anterior perirenal fascia (fused with retrocolic/mesocolic) fascia; 4, caecum/ascending colon; 5, right kidney parenchyma; 6, right perirenal space
7, right posterior pararenal space (the posterior perirenal fascia is difficult to identify); 8, right quadratus lumborum; 9, right psoas major; 10, inferior
vena cava; 11, abdominal aorta; 12, left psoas major; 13, left quadratus lumborum; 14, left erector spinae group; 15, left kidney parenchyma; 16, left
posterior perirenal fascia; 17, left perirenal space; 18, left posterior pararenal space; 19, descending colon. B, A coronal section through the appendix.
Key: 1, thickened and inflamed retrocaecal appendix; 2, inflammatory fluid and oedema extending along right mesocolon towards root of mesentery;
3, enlarged inflamed right ileocolic lymph node; 4, inflammatory fluid tracking in right mesocolon; 5, inferior vena cava – retrohepatic segment; 6,
inferior vena cava – infrahepatic peritonealized segment; 7, inferior vena cava – renal segment; 8, inferior vena cava – infrarenal segment; 9, left renal
vein; 10, superior mesenteric artery; 11, coeliac trunk; 12, abdominal aorta; 13, right common iliac artery; 14, left common iliac artery (origin); 15, tail of
pancreas.
Psoas major, psoas minor and iliacus
Psoas major and iliacus are functionally important in the lower limb
and are described together with psoas minor in Chapter 80.
Posterior abdominal wall hernias
In the absence of a previous surgical incision, herniation through the
posterior abdominal wall is rare because the muscular and fascial layers
4 usually protect against protrusion of the posterior abdominal viscera,
which are relatively immobile. However, the posterior free border of
7 4
external oblique, the inferior free border of latissimus dorsi, and the
8 6 iliac crest delimit the lumbar triangle (of Petit), an area of potential
9
13 14 weakness through which a lumbar hernia may develop (Stamatiou et al
2 2009).
5
10
1
3
11 VASCULAR SUPPLY AND LYMPHATIC DRAINAGE
3
12 ABDOMINAL AORTA
The abdominal aorta begins at the aortic hiatus of the diaphragm,
anterior to the twelfth thoracic vertebra (Mirjalili et al 2012a). It
descends anterior to the lumbar vertebrae and bifurcates into two
Fig. 62.6 A 61-year-old male with mid-ureteric calculus causing high-
common iliac arteries anterior to the fourth lumbar vertebra or the L4/5
grade obstruction of the left ureter and extravasation of urine from the left
intervertebral disc, slightly to the left of the midline (Mirjalili et al
renal hilum. Oral and intravenous contrast-enhanced CT. A transverse
2012b, Moussallem et al 2012) (Figs 62.8–62.10). The angle of bifurca-
section through the left renal hilum (the calculus is below the plane of this
tion is very variable (Moussallem et al 2012). The mean adult infrarenal
section). Key: 1, left kidney parenchyma; 2, extravasated urine in left
aortic diameter measured by computed tomography is 19–21 mm in
perirenal space; 3, posterior perirenal fascia; 4, anterior perirenal fascia
(fused medially with retropancreatic fascia and fused laterally with right men and 16–18 mm in women (Rogers et al 2013), but there are ethnic
leaf of descending mesocolon); 5, left posterior pararenal space; 6, variations (Jasper et al 2014). Measured by ultrasound, equivalent
descending colon; 7, third part of duodenum; 8, inferior vena cava; 9, values are 20 mm (SD 2.5 mm) in men and 17 mm (SD 1.5 mm) in
abdominal aorta; 10, right psoas major; 11, right quadratus lumborum; women (Needleman 2006). The mean calibre of the abdominal aorta
12, right erector spinae group; 13, aortocaval lymph node (borderline decreases slightly from proximal to distal. With advancing age, there is
enlarged); 14, left para-aortic lymph nodes (borderline enlarged). a progressive increase in abdominal aortic diameter in both sexes and | 1,509 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Psoas major Psoas minor Lumbar vessels Transversus abdominis posterior to the abdominal aorta. Lumbar arteries arise from its dorsal
aspect, and the third and fourth (and sometimes the second) left
lumbar veins cross behind it to reach the inferior vena cava. The
abdominal aorta may overlap the medial border of the left psoas major
muscle.
On the right, the abdominal aorta is related superiorly to the cisterna
chyli and thoracic duct, the azygos vein and the right crus of the dia-
phragm, which overlaps and separates it from the inferior vena cava and
right coeliac ganglion. Below the second lumbar vertebra, it is closely
applied to the left side of the inferior vena cava. This close relationship
allows the development of an aortocaval fistula, which is a rare com-
plication of aneurysmal disease or trauma. On the left, the aorta is
related superiorly to the left crus of the diaphragm and left coeliac
ganglion. Level with the second lumbar vertebra, it is related to the
fourth part of the duodenum, the left sympathetic trunk, and the infe-
rior mesenteric vein.
Branches
The branches of the aorta are described as anterior, lateral and dorsal
(see Figs 62.8–62.10). The anterior (unpaired) and lateral (paired)
branches are distributed to the viscera, while the dorsal branches supply
the body wall, vertebral column, vertebral canal and its contents. The
aorta terminates by dividing into the right and left common iliac
arteries.
Anterior group
Coeliac trunk
The coeliac trunk is the first anterior branch and arises just below the
aortic hiatus, usually at the level of the vertebral body of T12. It is
1–3 cm long and passes almost horizontally forwards and slightly to
Iliacus Quadratus lumborum the right above the body of the pancreas and splenic vein. In most
individuals, it trifurcates into the left gastric, common hepatic and
splenic arteries. Variations occasionally occur and include a separate
origin of the left gastric artery from the abdominal aorta, one or both
inferior phrenic arteries arising from the coeliac trunk, and the superior
mesenteric artery or one or more of its branches arising in common
with the coeliac trunk (Panagouli et al 2013). Anterior to the coeliac
Fig. 62.7 Bones and deep muscles of the posterior abdominal wall. Left trunk lies the lesser sac. The coeliac plexus surrounds the trunk, sending
psoas major and the diaphragm have been removed. (Adapted from extensions along its branches. On the right lie the right coeliac ganglion,
Drake RL, Vogl AW, Mitchell A (eds), Gray’s Anatomy for Students, right crus of the diaphragm and the caudate lobe of the liver. To the left
2nd ed, Elsevier, Churchill Livingstone. Copyright 2010.) lies the left coeliac ganglion, left crus of the diaphragm and the cardiac
region of the stomach. Rarely, the coeliac trunk can be compressed
by the median arcuate ligament, resulting in visceral ischaemia and
abdominal pain (Loukas et al 2007a).
superior mesenteric artery
the tapering becomes more pronounced (Fleischmann et al 2001). In
The superior mesenteric artery originates from the aorta approximately
the elderly, the abdominal aorta frequently becomes ectatic and tortu-
1–2 cm below the coeliac trunk, at the level of the L1 vertebral body
ous, changing the angle and position of the bifurcation and rotating
(Mirjalili et al 2012b) (Chs 65–66). It lies posterior to the body of the
the origins of the major branches.
pancreas and splenic vein, and is separated from the aorta by the left
Approximately 80% of abdominal aortic aneurysms occur in the
renal vein. It passes forwards and inferiorly, anterior to the uncinate
infrarenal segment of the aorta. Men with atherosclerosis are most at
process of the pancreas and the third part of the duodenum, to enter
risk of developing the condition, particularly from the sixth decade
the root of the small bowel mesentery and supply the midgut. Numer-
onwards (Takayama and Yamanouchi 2013). The high mortality risk
ous anatomical variants have been described (Bergman et al 2014), the
from spontaneous rupture has prompted the development of ultra-
most common being an accessory or replaced right hepatic artery
sound screening programmes to detect occult aneurysms and repair
arising near the origin of the superior mesenteric artery. Present in
them electively. The most common clinical cut-off diameter for the
about 15% of individuals, the accessory or replaced right hepatic artery
presence of an abdominal aortic aneurysm is 3 cm (Needleman 2006,
courses posterior to the portal vein and ascends posterolateral to the
Wegener 1992, Allan 2006, Moeller and Reif 2000). Repair is most
common bile duct (Winston et al 2007).
commonly performed by open surgery or endovascular stenting
(endovascular aneurysm repair). inferior mesenteric artery
The inferior mesenteric artery is smaller than the superior mesenteric
Relations
artery. It arises from the anterior or left anterolateral aspect of the aorta
at about the level of the L3 vertebral body, 3 or 4 cm above the aortic
The upper abdominal aorta is directly related anteriorly to the coeliac bifurcation and posterior to the inferior border of the horizontal part
trunk and its branches, autonomic nerve plexuses and lymphatics. of the duodenum (Ch. 66).
Below the coeliac trunk, the superior mesenteric artery leaves the aorta,
Lateral group
descending anterior to the left renal vein. Anterior to these vessels lies
the body of the pancreas, with the splenic vein on its posterior surface, suprarenal artery
extending obliquely up and to the left (see Fig. 62.8). Further anteriorly, The right and left middle suprarenal arteries arise from each side of the
the lesser sac separates the upper abdominal aorta from the lesser abdominal aorta, level with the superior mesenteric artery. Each passes
omentum, stomach and left lobe of the liver. Below the pancreas, the laterally over the crus of the diaphragm to the suprarenal gland, where
horizontal third part of the duodenum crosses the aorta anteriorly. The it anastomoses with the suprarenal branches of the ipsilateral inferior
most inferior part of the abdominal aorta is covered by the posterior phrenic and renal arteries (Toni et al 1988) (Ch. 71). The right middle
parietal peritoneum and crossed obliquely by the origin of the small suprarenal artery passes behind the inferior vena cava, near the right
bowel mesentery. coeliac ganglion. The left middle suprarenal artery passes close to the
The twelfth thoracic vertebra, the upper four lumbar vertebrae, inter- left coeliac ganglion, splenic artery and the superior border of the
vening intervertebral discs and the anterior longitudinal ligament lie pancreas. | 1,510 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Inferior phrenic veins
Hepatic veins
Oesophageal opening
Inferior vena cava Oesophagus
Left inferior phrenic artery
Right suprarenal gland Coeliac trunk
Right inferior phrenic artery
Right kidney Left renal vein
Left kidney
Superior mesenteric artery
Superior mesenteric vein Subcostal nerve
Iliohypogastric nerve
Transversus abdominis Left ureter
Quadratus lumborum Inferior mesenteric artery
Right gonadal vessels Abdominal aorta
Left gonadal vessels
Ilioinguinal nerve
Iliacus
Psoas minor
Lateral femoral cutaneous nerve Psoas major
Left common iliac artery
Genitofemoral nerve Left common iliac vein
Femoral nerve
Fig. 62.8 The abdominal aorta and inferior vena cava, and their branches. The fasciae, lymphatics and connective tissue have been removed for clarity.
renal artery
Anterior Dorsal Lateral
The renal arteries are two of the largest branches of the abdominal aorta
and arise laterally just below the origin of the superior mesenteric artery
at about the level of the L1 vertebral body (Mirjalili et al 2012b) (Ch.
Inferior 74). When the arteries arise at different cranio-caudal levels, the right
phrenic ostium is more commonly higher than the left. The right renal artery is
Coeliac
Middle longer and passes posterior to the inferior vena cava, right renal vein,
suprarenal head of the pancreas and second part of the duodenum. The left renal
Superior
artery passes behind the left renal vein, the body of the pancreas and
mesenteric Renal
the splenic vein. Variations in the number, origin, course and branching
patterns of the renal arteries are common.
First lumbar
Gonadal artery
L2
The gonadal arteries are two long, slender vessels that arise from the
aorta a little inferior to the renal arteries. Each passes inferolaterally
Second lumbar
under the parietal peritoneum on psoas major to supply the ipsilateral
Inferior Gonadal gonad (Chs 76–77). One or both gonadal arteries may arise from a
mesenteric
renal artery or be double.
L3
Psoas major
Third lumbar Dorsal group
inferior phrenic arteries
The inferior phrenic arteries usually arise either from the aorta, just
Psoas major
L4 above the level of the coeliac trunk, or directly from the coeliac trunk;
tendinous
arches Fourth lumbar occasionally, they originate from the renal artery (Loukas et al 2005a,
Gwon et al 2007). They contribute to the arterial supply of the dia-
phragm. Each artery ascends laterally, anterior to the crus of the dia-
phragm, near the medial border of the ipsilateral suprarenal gland. It
then divides into an ascending and a descending branch. The left
ascending branch passes behind the oesophagus and then runs anteri-
L5 orly on the left side of the oesophageal hiatus, where it bifurcates; one
branch curves forwards to anastomose with its counterpart in front of
the central tendon of the diaphragm and the other branch approaches
the thoracic wall to anastomose with the musculophrenic and pericar-
diacophrenic arteries. The right ascending branch passes behind the
Common iliac Median sacral
inferior vena cava and then bifurcates; one branch runs anteriorly on
Fig. 62.9 The branches of the abdominal aorta. the right side of the diaphragmatic opening for the inferior vena cava
(which it supplies) before anastomosing with its counterpart in front
of the central tendon of the diaphragm, and the other branch passes | 1,511 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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phrenic
27
3
34 4
Hepatic veins
28 12 7
13
10
9125
6
8
29 14
11
12
30 15 12
Hemiazygos
Left suprarenal
17 vein
31
Right
Subcostal
suprarenal
18 19 Lumbar azygos
33
Right renal Left gonadal vein
First lumbar
32
Ascending lumbar
23 Right gonadal
Second lumbar
24 21 16 22
26 Third lumbar
Third lumbar
20
25
Fourth lumbar
Fourth lumbar
Fig. 62.10 The abdominal aorta and its branches. A 36-year-old female
investigated by CT aortogram for possible Marfan’s aortic dissection; only
the normal abdominal aorta part of the dataset is shown in this three- Iliolumbar
dimensional reconstruction. Surface shaded display. Key: 1, apex of left
Common iliac
ventricle; 2, low thoracic aorta; 3, approximate position of diaphragmatic
hiatus; 4, coeliac trunk; 5, common hepatic artery; 6, splenic artery; 7, left
gastric artery; 8, proper hepatic artery; 9, left hepatic artery; 10, right
hepatic artery; 11, gastroduodenal artery; 12, superior mesenteric artery;
13, right renal artery; 14, left renal artery partly obscured by proper Median sacral
hepatic artery lying more superficial (with arrow); 15, inferior mesenteric
Fig. 62.11 Tributaries of the inferior vena cava and lumbar veins. Only the
artery; 16, superior rectal artery; 17, aortic bifurcation in front of L4; 18,
left lumbar venous system is shown, for clarity.
right common iliac artery; 19, left common iliac artery; 20, right external
iliac artery; 21, right internal iliac artery; 22, left external iliac artery; 23,
left internal iliac artery; 24, right superior gluteal artery; 25, right inferior
spinal branch known as the arteria radicularis magna (the artery of
epigastric artery; 26, left inferior epigastric artery; 27, right T12 segmental
Adamkiewicz) (p. 770), which frequently originates from an upper
artery; 28, right L1 segmental artery; 29, right L2 segmental artery; 30,
right L3 segmental artery; 31, right L4 segmental artery; 32, right lumbar artery, particularly on the left side (Biglioli et al 2004) (Ch. 45).
iliolumbar artery; 33, median sacral artery; 34, right superior epigastric Injury to this vessel, e.g. during thoracoabdominal aortic surgery, can
artery (continuing from right internal thoracic artery). cause spinal cord infarction.
The lateral branch of each lumbar artery runs posterior to psoas
major and the lumbar plexus, then across the anterior surface of quad-
laterally on the undersurface of the diaphragm. The descending branches ratus lumborum, before piercing the posterior limit of transversus
on each side supply the muscular diaphragm and anastomose with the abdominis to run forwards between it and the internal oblique. Perfo-
lower posterior intercostal and musculophrenic arteries. Each inferior rating branches pass posteriorly to supply the muscles and skin of the
phrenic artery gives off two or three small suprarenal branches. The posterior abdominal wall (Kiil et al 2009). The lumbar arteries anasto-
abdominal oesophagus, capsule of the liver, and upper pole of the mose with one another and the lower posterior intercostal, subcostal,
spleen may also receive small arterial twigs. iliolumbar, deep circumflex iliac and inferior epigastric arteries.
The inferior phrenic artery may be a source of significant collateral The dorsal branch of each lumbar artery passes backwards between
blood flow to large hepatocellular cancers and is sometimes specifically the adjacent transverse vertebral processes to supply the dorsal muscles,
occluded, along with the relevant hepatic artery, when treating such vertebrae, joints and skin of the back.
tumours by arterial embolization.
median sacral artery
lumbar arteries The median sacral artery is a small branch that arises from the posterior
There are usually four lumbar arteries on each side, in series with the aspect of the aorta a little above its bifurcation. It descends close to the
posterior intercostal arteries. They arise from the posterolateral aspect midline, anterior to the fourth and fifth lumbar vertebrae, sacrum and
of the abdominal aorta, opposite the lumbar vertebrae. A fifth, smaller, coccyx. At the level of the fifth lumbar vertebra, it is crossed by the left
pair occasionally arise from the median sacral artery, but lumbar common iliac vein and often gives off a small lumbar artery (arteria
branches of the iliolumbar arteries often take their place. The lumbar lumbales imae), small branches of which reach the anorectum via the
arteries run posterolaterally on the first to the fourth lumbar vertebral anococcygeal ligament. Anterior to the fifth lumbar vertebra, the median
bodies, passing behind the sympathetic trunk and tendinous arches sacral artery anastomoses with a lumbar branch of the iliolumbar artery.
formed by the attachments of psoas major to the vertebral bodies. The Anterior to the sacrum, it anastomoses with the lateral sacral arteries
right lumbar arteries pass posterior to the inferior vena cava. The upper and sends branches into the anterior sacral foramina.
two right lumbar arteries and the first left lumbar artery lie behind the
corresponding crus of the diaphragm. Just beyond the intervertebral
foramina, each lumbar artery divides into a medial branch, which gives INFERIOR VENA CAVA
off spinal and ganglionic branches; a middle branch, from which dorsal
and anastomotic branches arise; and a lateral branch, which supplies The inferior vena cava (Figs 62.11–62.12) conveys blood to the right
the abdominal wall (Arslan et al 2011). Of particular importance is the atrium from almost all of the structures below the diaphragm. Most of | 1,512 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Vascular supply and lymphatic drainage
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iliac artery. From below upwards, its anterior surface is crossed obliquely
1 by the root of the small bowel mesentery and its contained vessels and
9
20 nerves, the right gonadal artery and the third part of the duodenum.
Further cranially, it lies behind the head of the pancreas and first part
of the duodenum, separated from these structures by the common bile
10 21 duct and portal vein. Above the duodenum, its anterior surface is
2 covered by the peritoneum of the posterior abdominal wall, which
22
forms the posterior wall of the epiploic foramen, and which separates
3 5 the inferior vena cava from the right free border of the lesser omentum
4
and its contents. Above this, it is intimately related to the liver
23
anteriorly.
The posterior relations of the inferior vena cava include the lower
6
three lumbar vertebral bodies and their intervertebral discs, the anterior
24
longitudinal ligament, sympathetic trunk, right third and fourth lumbar
11
arteries, and the right psoas major. Superior to these structures, the
inferior vena cava is related posteriorly to the right renal and middle
suprarenal arteries, the medial part of the right suprarenal gland, the
25
12 7 right coeliac ganglion and the right inferior phrenic arteries.
14 The right ureter, medial border of the right kidney, second part of
26 8 the duodenum, and the right lobe of the liver are all lateral to the right
side of the inferior vena cava. The abdominal aorta, right crus of the
diaphragm and the caudate lobe of the liver are left-sided relations.
The normal diameter of the adult inferior vena cava is up to 30 mm
15
(Moeller and Reif 2000); its cross-sectional shape and calibre reflect the
16 13 degree of venous filling. Anatomical variants of the inferior vena cava
related to its complex embryogenesis are well described. Among these
17 18 are a double inferior vena cava (the left-sided vessel usually joins the
19 left renal vein); azygos continuation of the inferior vena cava; or a left-
sided inferior vena cava (which may exist in isolation or as part of situs
inversus) (Ang et al 2013, Spentzouris et al 2014).
Tributaries
The inferior vena cava usually receives the common iliac veins at its
origin and the lumbar, right gonadal, renal, right suprarenal, hepatic
and inferior phrenic veins throughout its course (see Figs 62.11–
62.12).
Fig. 62.12 A 41-year-old male investigated for microscopic haematuria.
Lumbar veins
CT intravenous urogram. Normal study. Late phase acquisition. Oblique
coronal, mid-abdominal 15 mm slab, maximal intensity projection (MIP) Four pairs of lumbar veins collect blood from the territories supplied
reformats. Key: 1, inferior vena cava, hepatic segment; 2, inferior vena by the corresponding lumbar arteries (see above), including the dorsal,
cava, peritonealized segment; 3, inferior vena cava, renal segment; 4, lateral and anterior abdominal wall. These branches anastomose pos-
right renal vein; 5, left renal vein crossing in front of the aorta; 6, inferior teriorly with tributaries of the azygos and hemiazygos veins, and ante-
vena cava, infrarenal segment; 7, inferior vena cava, confluence (partly riorly with branches of the epigastric, circumflex iliac and lateral
obscured by right common iliac artery); 8, left common iliac vein (coursing thoracic veins. These superficial anastomoses provide alternative routes
posteriorly out of slab; right common iliac vein obscured); 9, right hepatic of venous drainage from the pelvis and lower limbs to the heart in
vein joining inferior vena cava; 10, liver parenchyma; 11, right kidney the presence of inferior vena caval obstruction. The lumbar veins also
lower pole parenchyma; 12, right ureter (with excreted contrast); 13, communicate with the external and internal vertebral venous plexuses,
urinary bladder (with excreted contrast); 14, right psoas major; 15, right providing an additional collateral pathway for venous return. The
iliacus; 16, right external iliac artery; 17, right external iliac vein; 18, left paired longitudinal ascending lumbar veins connect ipsilateral lumbar
external iliac artery; 19, left external iliac vein; 20, low thoracic aorta; 21, veins. The third and fourth lumbar veins usually pass forwards on the
coeliac axis; 22, superior mesenteric artery; 23, right renal artery passing
sides of the corresponding vertebral bodies to enter the posterior
behind inferior vena cava; 24, aorta, infrarenal segment; 25, aortic
aspect of the inferior vena cava; the left lumbar veins pass behind the
bifurcation (partly obscured); 26, right common iliac artery (left common
abdominal aorta and are, therefore, longer. The first and second
iliac artery courses posteriorly out of slab).
lumbar veins are much more variable; they may drain into the inferior
vena cava, ascending lumbar, lumbar azygos and renal vein (on the
left), and are often connected to each other. Indeed, the first lumbar
vein often passes inferiorly to join the second lumbar vein or, less
its course is within the abdomen, but a small segment lies within the
commonly, drains directly into the ascending lumbar vein or passes
pericardium in the thorax.
forwards over the L1 vertebral body to join the lumbar azygos vein.
The inferior vena cava is formed by the junction of the left and right
The second lumbar vein may join the inferior vena cava at or near the
common iliac veins anterior to the fifth lumbar vertebral body, about
level of the renal veins or, less commonly, joins the third lumbar or
1 cm to the right of the midline. It ascends anterior to the vertebral
ascending lumbar vein.
column, to the right of the aorta, and lies in a deep groove on the
posterior surface of the liver, sometimes completely embedded by liver Ascending lumbar veins
tissue. It traverses the central tendon of the diaphragm between its
The paired ascending lumbar veins run medial to psoas major and
median and right ‘leaves’, and passes through the fibrous pericardium
connect ipsilateral common iliac, iliolumbar and lumbar veins. The
and a posterior inflection of the serous pericardium to open into the
ascending lumbar vein is variable in its course and connections; rarely,
posteroinferior part of the right atrium. The abdominal portion of the
the whole vein or a segment may be absent on one side (Lolis et al
inferior vena cava is devoid of valves.
2011). It commonly joins the subcostal vein to form the azygos vein on
The inferior vena cava can be encircled and controlled between the
the right and the hemiazygos on the left. The azygos and hemiazygos
renal veins below and the hepatic veins above (e.g. when operating on
veins run forwards over the twelfth thoracic vertebral body, and pass
a renal cell carcinoma extending into the inferior vena cava).
deep to or through the right and left crus of the diaphragm, respectively,
into the thorax (Ch. 56). The ascending lumbar vein is usually joined
Relations of the abdominal part of the
by a small vein, the lumbar azygos vein, from the back of the inferior
inferior vena cava
vena cava or left renal vein. Sometimes, the ascending lumbar vein ends
in the first lumbar vein, which then joins the lumbar azygos vein at the
The inferior vena cava lies behind the peritoneum of the posterior level of the first lumbar vertebra. Blood flow in the ascending lumbar
abdominal wall. At its origin, it is related anteriorly to the right common veins can occur in either direction (Morita et al 2007). | 1,513 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Posterior abdominal wall and retroPeritoneum
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Gonadal veins (approximately L2); the pattern of lymphatic spread from a testicular
malignancy suggests that lymph from the left testis drains to left para-
The right gonadal vein enters the inferior vena cava directly on its right
aortic nodes en route to the cisterna chyli, whereas lymph from the
anterolateral aspect at an acute angle about 2 cm inferior to the left
right testis drains to right and then left para-aortic nodes before reach-
renal vein in adults; occasionally, it drains into the right renal vein
ing the cisterna chyli. Lymph from the ovary may also drain via lym-
(Barber et al 2012). The left gonadal vein terminates in the left renal
phatics in the broad ligament and round ligament to internal iliac and
vein. Both veins may be replaced by multiple vessels in the lower
inguinal lymph nodes, respectively. Lymphatic drainage of the ureters
abdomen and sometimes remain double as far as their termination. Of
is less well defined but follows a regional pattern to nearby nodes.
the two gonadal veins, the left is more prone to develop venous
The lymphatic drainage of the retroperitoneal colon and rectum is
incompetence.
described in Chapter 66. The pancreas drains to numerous peripancre-
Renal veins atic nodes (Ch. 69) as well as portal, splenic, paracaval, superior
The renal veins are large-calibre vessels, which lie anterior to the renal mesenteric and coeliac nodes. The lymphatic drainage of the duode-
arteries and open into the inferior vena cava almost at right angles (Ch. num is not well described but the lymphatics generally drain to nodal
74). The left is three times longer than the right (approximately 7.5 cm stations related to local arteries (Ch. 65). Whilst the clinical pattern of
and 2.5 cm, respectively). The left vein lies on the posterior abdominal nodal metastases usually reflects normal lymphatic drainage pathways,
wall posterior to the splenic vein and body of the pancreas. It passes to the lymphatic obstruction may lead to metastases at unusual nodal sites.
right in the angle between the abdominal aorta posteriorly and the supe-
rior mesenteric artery anteriorly, to empty into the inferior vena cava. Cisterna chyli and abdominal lymph trunks
Occasionally, the left renal vein or an accessory left renal vein is retro-
aortic. The right renal vein lies posterior to the second part of the duode- The abdominal origin of the thoracic duct usually lies to the right of
num and, sometimes, the lateral part of the head of the pancreas. the midline at the level of the twelfth thoracic vertebral body or the
Suprarenal vein thoracolumbar intervertebral disc. It receives almost all the lymph from
below the diaphragm via the cisterna chyli, a localized lymphatic dila-
Most commonly, a single vein drains each suprarenal gland (Ch. 71).
tion formed most commonly by the union of the intestinal lymph trunk
The short right suprarenal vein drains directly into the inferior vena cava
and the left lumbar trunk (Phang et al 2014). The cisterna chyli is a
at the level of the twelfth thoracic vertebra; the longer left vein usually
saccular or fusiform lymphatic dilation measuring, on average, about
joins the left renal vein and may receive the left inferior phrenic vein.
1 cm wide and 2 cm long in the cadaver (Loukas et al 2007b). Recent
Numerous anatomical variations have been described (Cesmebasi et al
studies using magnetic resonance imaging (MRI) in vivo have shown
2014).
remarkable postural variations in the cross-sectional area of the cisterna
Inferior phrenic veins chyli, which expands considerably when moving from supine to sitting,
and again from sitting to standing (Niggemann et al 2010). The cisterna
The inferior phrenic veins usually originate on the superior surface of
chyli usually lies in front of the first and second lumbar vertebrae behind
the diaphragm but run mostly on its inferior surface to drain into the
the right crus of the diaphragm to the right of the abdominal aorta but
posterolateral aspect of the inferior vena cava. Both veins receive several
may be located at a higher vertebral level. The formation of the cisterna
diaphragmatic tributaries. The left vein runs to the left of the oesopha-
chyli is variable. The most common configuration, found in approxi-
geal hiatus, whereas the right courses to the right of the opening in the
mately two-thirds of individuals, is a single structure formed from the
diaphragm for the inferior vena cava, each receiving an oesophageal
union of the intestinal lymph trunk and the left (or, less commonly,
tributary (Loukas et al 2005b). Further, the left inferior phrenic vein
the right) lumbar lymph trunk (Loukas et al 2007b). In most other
frequently communicates with the left gastric vein and hence may
individuals, it is formed by the confluence of the intestinal and both
become prominent in portal hypertension. Both inferior phrenic veins
lumbar lymph trunks, with additional small branches from intercostal
usually drain directly into the inferior vena cava just below the dia-
lymphatics and retro-aortic lymph nodes. The upper two right lumbar
phragm, sometimes joining anteriorly to form a short common trunk.
arteries and the right lumbar azygos vein lie between the cisterna chyli
The right may occasionally drain into the right hepatic vein or inferior
and the vertebral column. The medial edge of the right crus of the
vena cava above the diaphragm. In contrast, the left frequently drains
diaphragm lies anterior to the abdominal confluence of lymph trunks.
into the left suprarenal, left renal or left hepatic vein.
The lumbar lymph trunks are formed by lymphatic vessels draining
Collaterals in inferior vena caval occlusion para-aortic nodes. The intestinal lymph trunk (which may be double)
Obstruction of the inferior vena cava from thrombosis, embolism, receives vessels draining from pre-aortic nodes, i.e. coeliac, superior and
extrinsic compression or intrinsic disease results in the development of inferior mesenteric nodes, which drain the entire abdominal gastroin-
an extensive venous collateral circulation via tributaries that ultimately testinal tract down to the anal canal. The thoracic duct leaves the supe-
connect to the superior vena cava. These include the azygos–hemiazygos rior end of the cisterna chyli and passes through the aortic hiatus of the
venous system, the vertebral venous plexuses, and superficial body wall diaphragm posterolateral to the right side of the aorta. Its thoracic
veins. The lumbar veins contribute significantly to these pathways continuation is described on page 979.
(Golub et al 1992). The major lymphatic vessels adjacent to the abdominal aorta are at
risk of injury during surgical procedures that involve peri-aortic dissec-
tion and/or lymphadenectomy. Damage to these lymphatic trunks or
their obstruction by malignant disease may cause major lymph leaks
LYMPHATIC DRAINAGE
manifesting as chylous ascites or chylothorax.
Lymph from the skin and subcutaneous tissues of the abdominal wall
drains via small-calibre superficial lymphatics to axillary and inguinal Retroperitoneal lymph node groups
nodes (Tourani et al 2013). The midline and the level of the umbilicus
form inconstant and variable watershed boundaries for these drainage The lymphatic drainage of the rectum, colon, stomach, pancreas,
territories. Lymphatics from the deeper layers of the body wall and the oesophagus and other organs is often described in terms of lymph node
abdominal and pelvic viscera drain almost exclusively to the cisterna stations and levels of dissection that relate to the management of malig-
chyli and thoracic duct. The former drains via ipsilateral retroperitoneal nant disease. The terminology and classification of retroperitoneal
lymph nodes that are concentrated around the external iliac and lymph nodes are based on their location. In classic anatomical descrip-
common iliac vessels and along the lateral aspects of the aorta and tions, the lymph nodes of the retroperitoneum around the abdominal
inferior vena cava. There is considerable overlap between the lymphatic aorta are grouped into pre-aortic, lateral or para-aortic, and retro-aortic
drainage basins of individual viscera. At certain sites, there is a cranio- groups (Fig. 62.13). However, it should be noted that adjacent nodal
caudal sequence of lymph nodes, e.g. para-oesophageal, retrocrural and groups merge into one another with no clear demarcating boundaries.
para-aortic nodes; mediastinal and gastro-oesophageal nodes; and para- Normal lymph node dimensions are very variable. Cross-sectional
sternal, superior and inferior epigastric nodes. Some lymphatic drainage imaging frequently uses 10 mm as an approximate measure for the
occurs directly across the diaphragm to the chest from the bare area of upper limit of normal lymph node dimensions in the adult (Moeller
the liver. and Reif 2000), even though some normal retroperitoneal nodes, such
The paired retroperitoneal viscera drain to lateral aortic (also termed as the portacaval node, are typically larger.
para-aortic) nodes around the origin of their arterial supply. Thus, the
Pre-aortic nodes
kidneys and suprarenal glands drain to nodes around the renal hilum
and to lateral aortic nodes around the origin of the renal arteries (L1–2 The pre-aortic nodes drain the gastrointestinal viscera, including
vertebral level). The testes drain to para-aortic and paracaval nodes the pancreas, liver, and spleen. These nodes lie anterior to the aorta | 1,514 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
innervation
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Pre-aortic Lateral chains. Lymphatic drainage from the right testis is via lymphatics travel-
ling with the gonadal vessels to the right para-aortic and aortocaval
nodes at the level of the second lumbar vertebra, whereas the left testis
drains to the left para-aortic nodes just inferior to the left renal vein
(Paño et al 2011).
Coeliac Iliac nodes
The paired iliac nodes are distributed around the common, external and
Abdominal confluence internal iliac arteries and veins. Constituent groups include: common
Suprarenal
of lymph trunks
Renal iliac, external iliac, internal iliac, circumflex iliac and obturator nodes.
Obturator nodes are located near the obturator foramen and, along
Superior
mesenteric Upper with the iliac nodes, are a common site of lymph node metastasis in
lateral
prostate cancer. ‘Pelvic side-wall’ nodes, lying adjacent to the ilium but
Right lumbar
not associated with a large artery or vein, are also described in the clini-
lymph trunk Gonadal
cal literature. The iliac nodes drain the pelvic viscera and walls, except
Intestinal for the ovaries and those parts of the rectum drained by superior rectal
lymph trunk
drainage pathways (see above). They also drain lymph from the inguinal
nodes and lower limbs.
Inferior
mesenteric
INNERVATION
The posterior abdominal wall contains the lumbar plexus and numer-
Lower
ous autonomic plexuses and ganglia, which lie close to the abdominal
lateral and
aorta and its branches (Fig. 62.14).
common iliac
Median sacral
LUMBAR PLEXUS
The lumbar ventral rami pass laterally into the posterior part of psoas
major, anterior to the transverse processes of the lumbar vertebrae; the
plexus lies in a coronal plane that is in line with the posterior part of
Fig. 62.13 Peri-aortic lymph node groups. The main pre-aortic groups are the vertebral body at L1 but becomes more anterior in the lower lumbar
shown. Only the left-sided lateral aortic (para-aortic) nodes are shown, for spine (Moro et al 2003, Benglis et al 2009) (see Fig. 62.14; Fig. 62.15).
clarity. N.B. The cisterna chyli is more commonly formed by the intestinal
The first four lumbar ventral rami, together with a contribution from
lymph trunk and the left lumbar lymph trunk (rather than the right lumbar
the twelfth thoracic ventral ramus (the dorsolumbar nerve), form the
lymph trunk shown in this diagram).
lumbar plexus. Although there are many variations, the most common
arrangement of the plexus is described here.
The first lumbar ventral ramus is joined by a branch from the twelfth
clustered around its anterior unpaired visceral arteries and can be sub- thoracic ventral ramus, and these roots contribute to the formation of
divided into coeliac, superior mesenteric and inferior mesenteric nodes. the iliohypogastric and ilioinguinal nerves, which run laterally on the
Efferent lymphatics from these nodes contribute to the formation of posterior abdominal wall (see Fig. 62.14). A branch from the ventral
the intestinal lymph trunk. ramus of L1 unites with a branch from the second lumbar ventral ramus
to form the genitofemoral nerve. The second, third and most of the
Coeliac nodes fourth lumbar ventral rami divide into ventral and dorsal divisions; the
These drain lymph from nodes around the stomach, hilum of the ventral divisions unite to form the obturator nerve, while most of
spleen, porta hepatis, cystic duct, lesser omentum, portacaval nodes, the nerve fibres in the dorsal divisions form the femoral nerve. The
peripancreatic nodes and pancreaticoduodenal nodes. They also receive remaining fibres from the fourth lumbar ventral ramus join the fifth
lymph from superior and inferior mesenteric lymph nodes. Efferent lumbar ventral ramus to form the lumbosacral trunk, which descends
lymphatics drain to the intestinal lymph trunk. to join the sacral plexus (p. 1229). Branches from the dorsal divisions
of the second and third lumbar rami unite to form the lateral femoral
superior mesenteric nodes cutaneous nerve (lateral cutaneous nerve of thigh). The accessory obtu-
There is extensive overlap with the drainage territory of coeliac nodes, rator nerve, when present, usually arises from the third and fourth
with subsidiary nodal groups that include peripancreatic, pancreatico- ventral divisions. The lumbar plexus is supplied by branches from the
duodenal, portacaval, small bowel mesenteric, ileocolic, mesocolic and lumbar vessels that supply psoas major.
inferior mesenteric nodes. Efferent lymphatics drain directly to the The branches of the lumbar plexus are listed in Table 62.1.
intestinal lymph trunk or via coeliac nodes. Division of constituent ventral rami into ventral and dorsal branches
is not as clear in the lumbar and sacral plexuses as it is in the brachial
inferior mesenteric nodes plexus. Lateral cutaneous branches of the twelfth thoracic and first
These nodes drain lymph from the hindgut, which includes the distal lumbar ventral rami are drawn into the gluteal skin, but otherwise these
transverse colon, descending and sigmoid colon, and rectum (including nerves are similar to intercostal nerves. The second lumbar ventral
superior rectal, mesorectal and presacral nodes). ramus is more complex. It not only contributes substantially to the
femoral and obturator nerves, but also has an anterior terminal branch
Lateral aortic groups
(the genital branch of the genitofemoral) and a lateral cutaneous
The lateral aortic (or para-aortic) nodes lie on either side of the abdomi- branch (which contributes to the lateral femoral cutaneous nerve and
nal aorta and inferior vena cava anterior to the medial margins of psoas the femoral branch of the genitofemoral nerve). Anterior terminal
major, diaphragmatic crura and sympathetic trunks. Constituent nodal branches of the third to fifth lumbar and first sacral rami are suppressed,
groups that are recognized clinically include: retrocrural (posterior to but the corresponding branches of the second and third sacral rami
the diaphragmatic crura at the aortic hiatus); left and right renal hilar; supply perineal skin.
and aortocaval, paracaval, retrocaval and precaval nodes. Retro-aortic The furcal nerve is an independent nerve with its own ventral and
lymph nodes are also para-aortic and are, therefore, sometimes included dorsal rootlets most commonly arising alongside the L4 nerve root. Its
within the lateral aortic group. The lateral aortic nodes drain into the branches contribute to the femoral and obturator nerves arising from
paired lumbar lymph trunks, one on each side, which terminate directly the lumbar plexus and to the lumbosacral trunk, which joins the sacral
or indirectly in the cisterna chyli and thoracic duct. Lymphatic connec- plexus (Harshavardhana and Dabke 2014). The term furcal refers to its
tions exist between lateral aortic, pre-aortic, retro-aortic and contralat- forked nature since it links the lumbar and sacral plexuses. Occasion-
eral lateral aortic nodes. ally, the furcal nerve arises at the level of the third or the fifth lumbar
The lateral aortic nodes drain the deep layers of the body wall, ret- nerve roots, in which case the sacral plexus is considered prefixed or
roperitoneal paired viscera (including the gonads) and the iliac nodal postfixed, respectively. | 1,515 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Oesophageal opening
Medial arcuate Aortic opening
T12
ligament
Lateral arcuate
L1 ligament
Twelfth rib
Left crus
L2 Psoas major (cut)
Quadratus
Subcostal nerve
lumborum
Iliohypogastric nerve
L3
Transversus Ilioinguinal nerve (cut)
abdominis
Psoas major L4
Psoas minor
Obturator nerve
Iliacus
L5
Lateral femoral
cutaneous nerve Lumbosacral trunk
Sympathetic trunk
Genitofemoral nerve
Sciatic nerve
Femoral nerve
Genital branch of the Psoas major (cut)
genitofemoral nerve
Fig. 62.14 Muscles and nerves of the posterior abdominal wall. The left psoas major has been removed to expose the origins of the lumbar plexus and
quadratus lumborum.
Inflammatory processes, such as retrocaecal appendicitis on the right Sensory
and diverticular abscess on the left, may occur in the posterior abdomi- The iliohypogastric nerve supplies sensory fibres to transversus
nal wall in the tissues immediately anterior to psoas major. These may abdominis, internal oblique and external oblique, and innervates the
irritate one or more branches of the lumbar plexus, causing pain or posterolateral gluteal and suprapubic skin.
sensory disturbance in the distribution of the affected nerves, e.g. the
skin of the thigh, hip or buttock. Injury
The nerve is occasionally injured by a surgical incision in the right iliac
Muscular branches fossa (e.g. during an inguinal hernia repair, open appendicectomy or
trocar placement) but there is rarely any noticeable sensory loss because
Small branches from the lumbar roots supply adjacent muscles such as the suprapubic skin is innervated from several sources. Division of the
psoas major and quadratus lumborum. iliohypogastric nerve above the anterior superior iliac spine may weaken
the posterior wall of the inguinal canal and predispose to formation of
Iliohypogastric nerve a direct inguinal hernia.
Distribution Ilioinguinal nerve
The iliohypogastric nerve usually originates from the L1 ventral ramus
but may arise wholly or in part from the T12 ventral ramus (Klaassen Distribution
et al 2011). It emerges from the upper lateral border of psoas major, The ilioinguinal nerve usually originates from the L1 ventral ramus but
and crosses obliquely behind the lower renal pole on the anterior may receive a contribution from T12 or L2 (Klaassen et al 2011). It
surface of quadratus lumborum. Above the iliac crest, it enters the emerges from the lateral border of psoas major, with or just inferior to
posterior part of transversus abdominis and then runs forwards between the iliohypogastric nerve. It passes obliquely across quadratus lumbo-
transversus abdominis and internal oblique, which it supplies. It gives rum and the upper part of iliacus and enters transversus abdominis
off a lateral cutaneous branch that pierces internal and external oblique about 3 cm medial and 4 cm inferior to the anterior superior iliac spine
above the iliac crest and supplies the posterolateral gluteal skin. It (in the adult); at this site, it is readily blocked by local anaesthetic. In
continues forwards, pierces the internal oblique approximately 3 cm this region, a branch may connect with the iliohypogastric or lateral
medial and 1 cm inferior to the anterior superior iliac spine (in adults), femoral cutaneous nerve (see Fig. 61.5). It pierces internal oblique a
and then penetrates the external oblique aponeurosis approximately little lower down, supplies it, and then traverses the inguinal canal
3 cm above and medial to the superficial inguinal ring to supply the superficial to the spermatic cord or round ligament. It emerges with the
suprapubic skin. The iliohypogastric nerve frequently connects with the cord from the superficial inguinal ring and divides into terminal sensory
ilioinguinal nerve and, less commonly, with the subcostal nerve (see branches.
Fig. 61.5). Numerous anatomical variations are described (Al-dabbagh 2002,
Ndiaye et al 2007). The ilioinguinal and genitofemoral nerves may
Motor interconnect within the inguinal canal and, consequently, each inner-
The iliohypogastric nerve contributes motor nerves to transversus vates the skin of the genitalia to a variable extent (Rab et al 2001,
abdominis and internal oblique, including the conjoint tendon. Cesmebasi et al 2015). The ilioinguinal nerve may pierce the external | 1,516 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
innervation
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T12 Iliohypogastric nerve
Ilioinguinal nerve
L1
Psoas major
L2
Nerve to iliacus
L3
Genitofemoral nerve
L4
Ventral branches of the ventral rami
L5 Femoral nerve
Dorsal branches of the ventral rami
S1
Superior and
Nerve to levator ani inferior gluteal nerves
and external anal sphincter
Sciatic nerve
Pudendal nerve
Perineal nerve
Dorsal nerve of penis or clitoris
Inguinal canal
Ilioinguinal nerve
Nerve to sartorius
Genital branch
Genitofemoral nerve
Femoral branch
Lateral
Obturator externus Intermediate Femoral cutaneous nerves
Medial
Adductor longus
Obturator nerve,
branches to Adductor brevis
Rectus femoris
Adductor magnus
Vastus lateralis
Gracilis Nerves to quadriceps
Vastus intermedius
Cutaneous branch of obturator nerve
Vastus medialis
Posterior femoral cutaneous nerve
Saphenous nerve
Common fibular
Sciatic nerve
Tibial
Fig. 62.15 The lumbar plexus and its branches.
Table 62.1 Branches of the lumbar plexus supplies its territory. Rarely, it may arise as a branch of the genitofemo-
ral nerve.
Muscular T12, L1–4
Iliohypogastric L1 Motor
Ilioinguinal L1 The ilioinguinal nerve supplies motor nerves to transversus abdominis
Genitofemoral L1, L2 and internal oblique; these fibres are given off before the nerve enters
Lateral femoral cutaneous L2, L3 the lateral end of the inguinal canal.
Femoral L2–4 dorsal divisions
Obturator L2–4 ventral divisions Sensory
Accessory obturator L3, L4 The ilioinguinal nerve supplies sensory fibres to transversus abdominis
and internal oblique. It innervates the skin of the proximal medial thigh
and the skin over the root of the penis and upper part of the scrotum
in males, or the skin covering the mons pubis and the adjoining labium
oblique aponeurosis proximal to the superficial inguinal ring or divide majus in females.
into terminal branches within the inguinal canal. It may form a
common trunk with the iliohypogastric nerve as far as the midpoint of Injury
the inguinal canal. It may be very small or completely absent, in which The nerve may be injured or entrapped during inguinal surgery, par-
case the iliohypogastric and genital branch of the genitofemoral nerves ticularly for inguinal hernia, leading to sensory disturbances and pain | 1,517 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Posterior abdominal wall and retroPeritoneum
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over the skin of the genitalia and upper medial thigh (Ndiaye et al Obturator nerve
2007).
The obturator nerve descends within the substance of psoas major to
Genitofemoral nerve emerge from its posteromedial border near the L5 vertebra (Kirchmair
et al 2008). It passes posterior to the common iliac vessels and lateral
Distribution to the internal iliac vessels. It then descends on the lateral wall of the
The genitofemoral nerve originates from the L1 and L2 ventral rami and pelvis attached to the fascia over obturator internus and lies antero-
is formed within the substance of psoas major. It descends obliquely superior to the obturator vessels before running into the obturator
forwards through the muscle to emerge on its anterior surface nearer foramen to enter the thigh. It has no branches in the abdomen or pelvis.
the medial border, opposite the third or fourth lumbar vertebra (Moro The further course and distribution are described on page 1372.
et al 2003). It then descends beneath the peritoneum on psoas major,
crosses obliquely behind the ureter, and divides into genital and femoral Accessory obturator nerve
branches; it may divide close to its origin such that its branches emerge
separately from psoas major. The genital branch crosses the lower part The accessory obturator nerve is sometimes present, more often on the
of the external iliac artery, enters the inguinal canal through the deep left (Katritsis et al 1980). It is usually formed by the ventral rami of L3
ring and accompanies the spermatic cord or round ligament. It exits the and L4. It emerges from the medial border of psoas major and runs
superficial inguinal ring, usually dorsal to the spermatic cord or round along the posterior surface of the superior pubic ramus posterior to
ligament, and supplies the cremaster muscle and skin of the external pectineus, where it gives off branches to supply pectineus and the
genitalia. The femoral branch descends lateral to the external iliac artery hip joint, and may join with the anterior branch of the obturator nerve
before crossing the deep circumflex iliac artery, to pass behind the (p. 1372).
inguinal ligament (occasionally, through it) (Rab et al 2001) and enter
the femoral sheath lateral to the femoral artery. It pierces the anterior
layer of the femoral sheath and fascia lata, and supplies the skin of the LUMBAR SYMPATHETIC SYSTEM
upper part of the femoral triangle. It may connect with the lateral
femoral cutaneous and intermediate femoral cutaneous nerves.
The lumbar part of each sympathetic trunk usually contains four inter-
connected ganglia lying in extraperitoneal connective tissue on the
Motor
anterolateral aspects of the lumbar vertebrae along the medial margin
The genitofemoral nerve innervates cremaster via the genital branch.
of psoas major (see Fig. 62.14). Superiorly, it is continuous with the
thoracic sympathetic trunk posterior to the medial arcuate ligament at
Sensory
the L1/2 vertebral level (Feigl et al 2011). Inferiorly, it passes posterior
The genitofemoral nerve innervates the skin of the scrotum in males,
to the common iliac vessels and is continuous with the sacral sympa-
or that of the mons pubis and labium majus in females, via its genital
thetic trunk. On the right side, it lies posterior to the inferior vena
branch; there is considerable overlap and variability with the cutaneous
cava; on the left, it is posterior to the lateral aortic lymph nodes. It is
distribution of the ilioinguinal nerve (Cesmebasi et al 2015). It also
anterior to most of the lumbar vessels but may pass behind some
innervates the anteromedial skin of the thigh via its femoral branch.
lumbar veins.
The genitofemoral nerve is also understood to play a critical role in
The first, second and, sometimes, the third lumbar ventral rami are
inguinoscrotal descent of the developing testis (Hutson et al 2015).
each connected to the lumbar sympathetic trunk by a white ramus
communicans. All lumbar ventral rami are joined near their origins by
Injury
long, slender grey rami communicantes from the four lumbar sympa-
Like the ilioinguinal nerve, the genital branch may be injured during
thetic ganglia. Their arrangement is irregular: one ganglion may give
inguinal surgery (open and laparoscopic), leading to neuralgic pain
rami to two or three lumbar ventral rami, one lumbar ventral ramus
(Cesmebasi et al 2015).
may receive rami from two ganglia, or grey rami may leave the sympa-
thetic trunk between ganglia (Murata et al 2003).
Femoral nerve
The lumbar sympathetic trunks are vulnerable during retroperito-
neal nodal dissection and their injury can impair seminal emission and
The femoral nerve descends through psoas major and emerges on or lead to retrograde ejaculation.
under its lateral border, about 4 cm above the inguinal ligament (Moore
and Stringer 2011). It passes between psoas major and iliacus deep to
the iliac fascia and runs posterior to the inguinal ligament into the LUMBAR PARASYMPATHETIC SYSTEM
thigh. It gives off branches that supply iliacus and pectineus, and sends
sensory fibres to the femoral artery. Posterior to the inguinal ligament,
The parasympathetic supply to the abdominal viscera is provided by
it lies lateral to the femoral artery and sheath. The further course and
the vagus nerve to the coeliac and superior mesenteric plexuses, and by
distribution are described on page 1372.
pelvic splanchnic nerves that are distributed through the hypogastric
and inferior mesenteric plexuses (Ch. 59).
Lateral femoral cutaneous nerve (lateral
cutaneous nerve of the thigh)
PARA-AORTIC BODIES
The lateral femoral cutaneous nerve (lateral cutaneous nerve of the
thigh) is usually derived from the ventral rami of L2 and 3, but variable The para-aortic bodies (also known as paraganglia or, collectively, as
contributions from L1 to L3 are described (de Ridder et al 1999). It the organ of Zuckerkandl) are collections of neural crest-derived
emerges from the posterolateral border of psoas major and crosses chromaffin tissue found in close relation to the aortic autonomic plex-
iliacus obliquely towards the anterior superior iliac spine. It supplies uses. They are relatively large in the fetus, where they may have a role
sensory fibres to the parietal peritoneum in the iliac fossa. On the right, in maintaining blood pressure by catecholamine secretion. They reach
the nerve passes posterolateral to the caecum, separated from it by the a maximum size at around 3 years of age, and have usually regressed
iliac fascia and peritoneum. The left nerve passes behind the lower part by adulthood. They are usually found as a pair of bodies lying antero-
of the descending colon. Both nerves usually pass behind the inguinal lateral to the aorta in the region of the inferior mesenteric and
ligament about 1–2 cm medial to the anterior superior iliac spine; superior hypogastric plexuses, but multiple smaller collections may
occasionally, they pass through or, rarely, anterior to the ligament (Ray be present. Occasionally, they are found as high as the coeliac plexus
et al 2010). Occasionally, the nerve lies anterior or superior to the ante- or as low as the inferior hypogastric plexus in the pelvis, or are
rior superior iliac spine as it enters the thigh. In the thigh, the lateral closely applied to the sympathetic ganglia of the lumbar chain.
femoral cutaneous nerve usually passes anterior or lateral to sartorius Scattered cells that persist into adulthood may, rarely, be the sites of
but may pierce the muscle. The further course and distribution are paraganglioma (extra-adrenal phaeochromocytoma) (Subramanian
described on page 1371. and Maker 2006). | 1,518 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Key references
KEY REFERENCES
Congdon ED, Blumberg R, Henry W 1942 Fasciae of fusion and elements Together with Klaassen et al 2011, these two papers provide a useful
of the fused enteric mesenteries in the human adult. Am J Anat 70: description of the anatomy of the ilioinguinal and iliohypogastric nerves and
251–9. underline the importance of the ilioinguinal nerve in clinical practice.
Culligan K, Remzi FH, Soop M et al 2013 Review of nomenclature in colonic Loukas M, Wartmann CT, Louis RG Jr et al 2007b Cisterna chyli: a detailed
surgery – proposal of a standardised nomenclature based on mesocolic anatomic investigation. Clin Anat 20:683–8.
anatomy. Surgeon 11:1–5. This article revises traditional concepts about the cisterna chyli and its
Making sense of mesocolic anatomy based on findings from modern formation.
investigative techniques.
Mirjalili SA, McFadden SL, Buckenham T et al 2012b A reappraisal of adult
Dodds WJ, Darweesh RMA, Lawson TL et al 1986 The retroperitoneal spaces abdominal surface anatomy. Clin Anat 25:844–50.
revisited. AJR Am J Roentgenol 147:1155–61. A paper that challenges some traditional surface anatomical landmarks by
An important radiologic perspective on the retroperitoneal ‘spaces’. investigating results from analysis of CT scans in living supine adults.
Klaassen Z, Marshall E, Tubbs RS et al 2011 Anatomy of the ilioinguinal and Willard FH, Vleeming A, Schuenke MD et al 2012 The thoracolumbar fascia:
iliohypogastric nerves with observations of their spinal nerve contribu- anatomy, function and clinical considerations. J Anat 221:507–36.
tions. Clin Anat 24:454–61. An evidence-based review of the complex and clinically important
Ndiaye A, Diop M, Ndoye JM et al 2007 Anatomical basis of neuropathies thoracolumbar fascia.
and damage to the ilioinguinal nerve during repairs of groin hernias
(about 100 dissections). Surg Radiol Anat 29:675–81. | 1,519 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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of injury in 110 hernia repairs. Surg Radiol Anat 24:102–7. aortic diameters in the Indian population using computed tomography.
Allan PL 2006 The aorta and the inferior vena cava. In: Allan PL, Dubbins J Postgrad Med 60:57–60.
PA, Pozniak MA et al (eds) Clinical Doppler Ultrasound, 2nd ed. Katritsis E, Anagnostopoulou S, Papadopoulos N 1980 Anatomical observa-
Edinburgh: Elsevier, Churchill Livingstone. tions on the accessory obturator nerve (based on 1000 specimens). Anat
Amin M, Blandford AT, Polk HC Jr 1976 Renal fascia of Gerota. Urology Anz 148:440–5.
7:1–3. Kiil BJ, Rozen WM, Pan WR et al 2009 The lumbar artery perforators: a
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Coffin A, Boulay-Coletta I, Sebbag-Sfez D et al 2015 Radioanatomy of the of the variations of the inferior phrenic vein. Surg Radiol Anat 27:
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Congdon ED, Edson JN 1941 The cone of renal fascia in the adult white Loukas M, Pinyard J, Vaid S et al 2007a Clinical anatomy of celiac artery
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Congdon ED, Blumberg R, Henry W 1942 Fasciae of fusion and elements Loukas M, Wartmann CT, Louis RG Jr et al 2007b Cisterna chyli: a detailed
of the fused enteric mesenteries in the human adult. Am J Anat 70: anatomic investigation. Clin Anat 20:683–8.
251–9. This article revises traditional concepts about the cisterna chyli and its
formation.
Culligan K, Remzi FH, Soop M et al 2013 Review of nomenclature in colonic
surgery – proposal of a standardised nomenclature based on mesocolic Mirjalili SA, Hale SJ, Buckenham T et al 2012a A reappraisal of adult thoracic
anatomy. Surgeon 11:1–5. surface anatomy. Clin Anat 25:827–34.
Making sense of mesocolic anatomy based on findings from modern Mirjalili SA, McFadden SL, Buckenham T et al 2012b A reappraisal of adult
investigative techniques. abdominal surface anatomy. Clin Anat 25:844–50.
Culligan K, Walsh S, Dunne C et al 2014 The mesocolon: a histological and A paper that challenges some traditional surface anatomical landmarks by
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de Ridder VA, de Lange S, Popta JV 1999 Anatomical variations of the lateral Moore AE, Stringer MD 2011 Iatrogenic femoral nerve injury: a systematic
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Morita S, Kimura T, Masukawa A et al 2007 Flow direction of ascending
Dodds WJ, Darweesh RMA, Lawson TL et al 1986 The retroperitoneal spaces lumbar veins on magnetic resonance angiography and venography:
revisited. AJR Am J Roentgenol 147:1155–61. would ‘descending lumbar veins’ be a more precise name physiologi-
An important radiologic perspective on the retroperitoneal ‘spaces’. cally? Abdom Imaging 32:749–53.
Feigl GC, Kastner M, Ulz H et al 2011 Topography of the lumbar sympathetic Moro T, Kikuchi S, Konno S et al 2003 An anatomic study of the lumbar
trunk in normal lumbar spines and spines with spondylophytes. Br J plexus with respect to retroperitoneal endoscopic surgery. Spine (Phila
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Fleischmann D, Hastie TJ, Dannegger FC et al 2001 Quantitative determina- Moussallem CD, Abou Hamad I, El-Yahchouchi CA et al 2012 Relationship
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Golub RM, Parsons RE, Sigel B et al 1992 A review of venous collaterals in Murata Y, Takahashi K, Yamagata M et al 2003 Variations in the number and
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Gwon DI, Ko GY, Yoon HK et al 2007 Inferior phrenic artery: anatomy, vari- cantes. Clin Anat 16:108–13.
ations, pathologic conditions, and interventional management. Radio- Ndiaye A, Diop M, Ndoye JM et al 2007 Anatomical basis of neuropathies
graphics 27:687–705. and damage to the ilioinguinal nerve during repairs of groin hernias
Harshavardhana NS, Dabke HV 2014 The furcal nerve revisited. Orthop Rev (about 100 dissections). Surg Radiol Anat 29:675–81.
(Pavia) 6:5428. Together with Klaassen et al 2011, these two papers provide a useful
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Hutson JM, Li R, Southwell BR et al 2015 Regulation of testicular descent. McGahan JP (eds) Atlas of Ultrasound Measurements, 2nd ed. Boston:
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Niggemann P, Förg A, Grosskurth D et al 2010 Postural effect on the size of Stamatiou D, Skandalakis JE, Skandalakis LJ et al 2009 Lumbar hernia:
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Rab M, Ebmer J, Dellon AL 2001 Anatomic variability of the ilioinguinal Tourani SS, Taylor GI, Ashton MW 2013 Anatomy of the superficial lymphat-
and genitofemoral nerve: implications for the treatment of groin pain. ics of the abdominal wall and the upper thigh and its implications in
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CHAPTER
63
Peritoneum and peritoneal cavity
The peritoneum is the largest serous membrane in the body, and its colic ligament (Meyers 1973). Passage across the midline to the left
arrangements are complex. In males it forms a closed sac, but in females subphrenic space is prevented by the falciform ligament. Peritoneal
it is open at the lateral ends of the uterine tubes. Although its smooth fluid flows in a predominantly clockwise direction around the perito-
appearance is unremarkable, its structure is complex and varies greatly neal cavity (Fig. 63.1); it reaches the surface of the greater omentum,
in different locations. Directly beneath the monolayer of mesothelium where it is processed by the immune system (Meyers et al 1987, Meyers
is a well-developed basement membrane, outside which is a rich lym- 1994). Malignant cells may become trapped within peritoneal recesses
phatic plexus. Microscopic mesothelial pores or peritoneal stomata are or in the milky spots of the greater omentum, where they may prolifer-
distributed throughout the peritoneum but particularly on the under- ate and produce visible and palpable tumour deposits. These sites must
surface of the diaphragm and anterior abdominal wall (Wassilev et al be deliberately examined when searching for peritoneal metastases
1998). At peritoneal stomata, the mesothelium is in close proximity to (Zonca et al 2008). Gross infiltration of the omentum by cancer, often
underlying lymphatic endothelial cells and there is no intervening base- referred to as an ‘omental cake’, emphasizes the capacity of the omentum
ment membrane. Both peritoneal stomata and sites of lymphoid aggre- to trap malignant cells. The movement of peritoneal fluid explains the
gates (‘milky spots’) in the omenta contribute to peritoneal fluid presence of disease at sites such as the undersurface of the right hemidi-
absorption, and their occlusion by malignant cells may result in ascites aphragm and the pelvic pouches. An example is the Fitz–Hugh–Curtis
(Hagiwara et al 1994). Neighbouring mesothelial cells are joined by syndrome, in which gonorrhoea or chlamydia organisms enter the peri-
junctional complexes but probably permit the passage of macrophages. toneal cavity through the uterine tubes and are transported in the
The submesothelial connective tissue may also contain macrophages, peritoneal fluid to the right upper quadrant, where they cause perihe-
lymphocytes and adipocytes (in some regions). Mesothelial cells may patic inflammation. Disruption of the integrity of the peritoneum by
transform into fibroblasts, which may play an important role in inflam- percutaneous puncture, laparoscopy or open surgery profoundly affects
mation of the peritoneum and the formation of peritoneal adhesions its defensive function and can create ‘sticky’ sites where pathogens or
after surgery (Schnüriger et al 2011). malignant cells can settle and proliferate.
The normal pressure within the peritoneal cavity is about 2–10 mmHg Direct communication of abdominal and pleural spaces called
(higher in pregnancy and obese individuals) (Sanchez et al 2001). It pleuro peritoneal fenestrae may rarely exist (Pestieau et al 2000,
can be measured directly using a catheter inserted into the abdomen, Simmons and Mir 1989).
or indirectly, by monitoring the pressure in the bladder or stomach. The
pressure inside the abdomen may increase after trauma as a result of
PERITONEAL ATTACHMENTS
the accumulation of blood, fluid or oedema, leading to an ‘abdominal
compartment syndrome’. In such patients, monitoring of intra-
abdominal pressure can identify major increases in pressure (above The parietal peritoneum is attached to the muscular layers of the
about 25 mmHg) that could jeopardize the blood flow to vital organs abdominal wall by extraperitoneal connective tissue. Around the
and dictate the need for urgent decompression. bladder and rectum, it is only loosely attached to allow for alterations
in the size of these viscera, whereas it is firmly adherent to the inferior
surface of the diaphragm and linea alba. The extraperitoneal tissue over
PERITONEAL FLUID
the posterior abdominal wall frequently contains large amounts of fat,
especially in obese males. The visceral peritoneum is firmly adherent to
The peritoneal cavity is a potential space between the parietal perito- the underlying viscera and often blends with connective tissue in the
neum, which lines the abdominal wall, and the visceral peritoneum, wall of the organ; it rarely contains loose connective or adipose tissue.
which covers the abdominal viscera and associated mesenteries within The visceral peritoneum is often considered as part of the underlying
the cavity. It contains a small amount of peritoneal fluid that rarely viscus for clinical and pathological purposes such as the staging of
exceeds 5 ml in healthy males and postmenopausal females (Yoshikawa cancer. Because of its attachments, removal of the parietal peritoneum
et al 2013). In healthy young females, up to 25 ml of fluid may be in the management of peritoneal metastases is possible without resec-
present, depending on the phase of the menstrual cycle (Koninckx et al tion of underlying tissues, whereas cancer deposits on visceral perito-
1980). The fluid lubricates the mobile viscera, allowing them to glide neum usually require partial resection of the viscus for complete
freely on the abdominal wall and against each other within the limits removal (see Video 63.1).
imposed by their attachments. However, the parietal peritoneum can
be surgically removed without necessarily having adverse effects on gut
GENERAL ARRANGEMENT OF THE PERITONEUM
function (Sugarbaker 2012). Normal peritoneal fluid contains water,
proteins (less than 30 g of protein per litre), electrolytes and solutes
derived from interstitial fluid in the adjacent tissues and from plasma The alimentary tract develops as a single tube suspended in the coe-
in local capillaries. It also contains a few cells, including desquamated lomic cavity by ventral and dorsal mesenteries (Ch. 60). Ultimately, the
mesothelium, nomadic peritoneal macrophages, mast cells, fibroblasts, ventral mesentery is largely resorbed, although some parts persist in the
lymphocytes and other leukocytes. Macrophages migrate freely between upper abdomen and form structures such as the lesser omentum and
the peritoneal cavity and the surrounding connective tissue. In females, falciform ligament. The mesenteries of the intestines in the adult are
blood or fluid may enter the peritoneal cavity from a ruptured ovarian the remnants of the dorsal mesentery. The migration and subsequent
follicle (mittelschmerz) or from the retrograde flow of menstrual fluid fixation of parts of the gastrointestinal tract produce the so-called ‘ret-
along the uterine tubes (which may cause endometriosis). Peritoneal roperitoneal’ segments of bowel (most of the duodenum, ascending
fluid is absorbed via peritoneal stomata and milky spots (see above). colon, descending colon, and rectum) (Fig. 63.2), and four separate
Under normal circumstances, the peritoneal cavity never contains gas. intraperitoneal bowel loops suspended by mesenteries of variable
The peritoneum and its fluid have important defensive properties lengths. These are all covered by visceral peritoneum, which is continu-
(Autio 1964). Peritoneal fluid gravitates to dependent sites within ous with the parietal peritoneum covering the posterior abdominal
the peritoneal cavity; diaphragmatic respiratory movements, negative wall. The first intraperitoneal loop is formed by the abdominal oesopha-
intrathoracic pressure and intestinal peristalsis encourage flow from the gus, stomach and first part of the duodenum. The second loop is made
pelvis to the subphrenic regions, even when the individual is erect. Fluid up of the duodenojejunal junction, jejunum, ileum and usually the
preferentially ascends from the lower abdomen and pelvis to the right caecum. The third loop contains the transverse colon, and the final loop
subhepatic and subphrenic ‘spaces’ via the right paracolic gutter, which contains the sigmoid colon and occasionally the distal descending
1098 is deeper than the left paracolic gutter and has no obstructing phrenico- colon. | 1,522 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
General arrangement of the peritoneum
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Falciform ligament Fig. 63.1 The peritoneal cavity.
Left subphrenic space Arrows indicate the flow of
peritoneal fluid. (Courtesy of CM
Left triangular ligament Brown, Office of Visual Media
Right subphrenic space IUSM 2011.)
Retrohepatic bare area
Lesser sac
Right triangular ligament
Phrenicocolic ligament
Right infracolic compartment
Left paracolic gutter
Root of the mesentery
Right paracolic gutter
Left infracolic compartment
Sigmoid mesocolon
Right pararectal space Left pararectal space
Where visceral peritoneum encloses or suspends organs within the and Hricak 1999). It has a complex attachment to the wall of the
peritoneal cavity, the peritoneum and related connective tissues form abdominal cavity and forms the falciform ligament, coronary liga-
‘peritoneal ligaments’, omenta or mesenteries. All but the greater ments, lesser omentum (gastrohepatic and hepatoduodenal ligaments),
omentum are composed of two layers of visceral peritoneum separated greater omentum (including the gastrocolic ligament), gastrosplenic
by variable amounts of fatty connective tissue. The greater omentum is ligament, splenorenal ligament and phrenicocolic ligament (see Fig.
folded back on itself and therefore consists of four layers of visceral 63.2; Figs 63.3–63.5).
peritoneum separated by variable amounts of adipose tissue. Mesenter-
ies attach their respective viscera to the posterior abdominal wall; the Falciform ligament
attachment of the mesentery of the small intestine to the posterior
abdominal wall is referred to as the root of the mesentery (see Fig.
The falciform ligament is a thin anteroposterior double fold of perito-
63.2). The mesenteries contain the neurovascular bundles and lym-
neum that connects the liver to the posterior aspect of the anterior
phatic channels that supply the suspended organs. In obese individuals,
abdominal wall just to the right of the midline. Adjacent to the ante-
extensive adipose tissue within the mesenteries and omenta may
rior abdominal wall, it contains a variable amount of fat (Feldberg and
obscure these neurovascular bundles. In contrast, in the very young, the
van Leeuwen 1990). It extends inferiorly to the level of the umbilicus
elderly or the malnourished, the mesenteries and omenta may contain
and superiorly it narrows to a depth of 1–2 cm as the distance between
little adipose tissue and the neurovascular bundles are more obvious.
the liver and anterior abdominal wall decreases. Its two peritoneal
Although they are described as intraperitoneal, the suspended
layers separate to enclose the liver, to which it is firmly adherent. Supe-
viscera, strictly speaking, do not lie within the peritoneal cavity because
riorly, the two peritoneal layers are continuous with the parietal
they are covered by visceral peritoneum. They are in continuity with
peritoneum on the undersurface of the diaphragm but are reflected
extraperitoneal tissues, including the retroperitoneum. The loose
laterally to form the superior layer of the coronary ligament of the liver
areolar connective tissue that forms the extraperitoneal and retroperi-
on the right and the left triangular ligament of the liver on the left. The
toneal tissues is often divided into potential ‘spaces’ as evidenced by
inferior aspect of the falciform ligament forms a free border, where the
the presence of discrete collections of fluid or blood in pathological
two peritoneal layers are continuous with each other as they enclose
conditions (see Figs 62.4–62.6).
the ligamentum teres. Because the peritoneum of the falciform liga-
ment is in continuity with that covering the posterior abdominal wall
and with the parietal peritoneum of the anterior abdominal wall,
PERITONEUM OF THE UPPER ABDOMEN blood from a retroperitoneal haemorrhage (commonly, acute haemor-
rhagic pancreatitis) may track between the folds of peritoneum and
The abdominal oesophagus, stomach, liver and spleen all lie within a appear as haemorrhagic discolouration around the umbilicus (Cullen’s
double fold of visceral peritoneum that runs from the posterior to the sign). The bloodstained fluid reaches the periumbilical region via the
anterior abdominal wall. This fold has no recognized name but has lesser omentum and falciform ligament or via the pararenal spaces and
been referred to as the mesogastrium, from which it is derived (Coakley abdominal wall. | 1,523 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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W X Y
Left triangular ligament of liver
Upper recess of lesser sac
A A
Oesophagus
Coronary ligament of liver
Left gastric artery
Splenorenal ligament
Right triangular ligament of liver Epiploic foramen
B B
Cut edge of lesser omentum Common hepatic artery
C C
Root of transverse mesocolon,
adherent to posterior layers
of greater omentum
Root of the mesentery
Root of sigmoid mesocolon
W X Y
Fig. 63.2 The posterior abdominal wall, showing the lines of peritoneal reflection, after removal of the liver, spleen, stomach, jejunum, ileum, caecum,
transverse colon and sigmoid colon. The various sessile (retroperitoneal) organs can be seen through the posterior parietal peritoneum. Note the
ascending and descending colon, duodenum, kidneys, suprarenal glands, pancreas and inferior vena cava. Line W–W represents the plane of Figure
63.3. Line X–X represents the plane of Figure 63.4. Line Y–Y represents the plane of Figure 63.5. Line A–A represents the plane of Figure 63.6A. Line
B–B represents the plane of Figure 63.6B. Line C–C represents the plane of Figure 63.6C.
Peritoneal connections of the liver
kidney is known as the hepatorenal pouch (of Morison) (Stringer
2009). In the supine position, this is the most dependent part of the
The liver is almost completely covered in visceral peritoneum; only the peritoneal cavity in the upper abdomen and is a site where fluid or
‘bare area’ posteriorly is in direct contact with the right hemidiaphragm. peritoneal metastases may localize.
Peritoneal ligaments run from the liver to the surrounding viscera and The lower layer of the coronary ligament is continuous with the
to the abdominal wall and diaphragm (see Fig. 63.2; Fig. 63.6); they peritoneum that descends over the anterior surface of the right kidney
are described in detail in Chapter 67. and to the front of the first part of the duodenum and hepatic flexure
The coronary ligament is formed by the reflection of the peritoneum of the colon (see Fig. 63.2). Medially, it passes in front of a short
from the diaphragm on to the superior and posterior surfaces of the segment of the inferior vena cava lying between the first part of the
right lobe of the liver. Between the two layers of this ligament, a large duodenum below and the caudate process of the liver above, forming
triangular area, the ‘bare area’ of the liver, is devoid of peritoneal cover- the posterior wall of the epiploic foramen. This narrow strip broadens
ing. Here, the liver is connected to the diaphragm by areolar tissue, out as the peritoneum continues across the midline on to the posterior
which is in continuity inferiorly with the anterior pararenal space. On wall of the lesser sac.
the right, the two layers of the coronary ligament converge laterally to The right triangular ligament is a short, V-shaped fold at the right
form the right triangular ligament. On the left, the two layers fuse to lateral limit of the bare area of the liver, where the two layers of the
form the left triangular ligament. The upper layer of the coronary liga- coronary ligament converge. It is continuous with the peritoneum of
ment is reflected superiorly on to the undersurface of the diaphragm the right posterolateral abdominal wall. Surgical division of the right
and inferiorly on to the right and superior surfaces of the liver. The triangular and coronary ligaments allows the right lobe of the liver to
lower layer of the coronary ligament is reflected inferiorly from the be retracted forwards, exposing the lateral aspect of the inferior vena
posterior surface of the liver on to the posterior abdominal wall over cava behind the liver.
the right suprarenal gland and kidney. The peritoneal recess formed The left triangular ligament is a double layer of peritoneum that
between the inferior surface of the liver and the upper pole of the right extends for a variable length over the superior border of the left lobe | 1,524 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
General arrangement of the peritoneum
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of the liver. Medially, the anterior leaf is continuous with the left layer ment allows the left lobe of the liver to be mobilized. The left triangular
of the falciform ligament, while the posterior layer is continuous with ligament is an important stabilizing factor for the left lobe after excision
the lesser omentum. The left triangular ligament lies in front of the of the right lobe of the liver.
abdominal oesophagus, the upper limits of the lesser omentum, and The peritoneum of the left triangular ligament is continuous with
part of the fundus of the stomach. Division of the left triangular liga- that lining the undersurface of the left dome of the diaphragm, which,
in turn, is continuous with that lining the posterior abdominal wall.
Here it passes behind the spleen on to the most lateral part of the
mesentery of the transverse colon and the splenic flexure. It continues
down lateral to the descending colon into the pelvis, forming the left
Diaphragm paracolic gutter. Medially, the peritoneum covering the left upper pos-
terior abdominal wall is reflected anteriorly to merge with the upper
Right subphrenic space end of the lesser omentum, the peritoneum overlying the left aspect of
the abdominal oesophagus, and the left layer of the gastrosplenic liga-
ment (see Fig. 63.2).
Bare area of the liver Parietal peritoneum lines the posterior abdominal wall over the
diaphragmatic crura, the upper abdominal aorta and its associated
branches, lymph nodes and nerve plexuses, and the upper anterior
surface of the pancreas. Below the liver, it continues down the posterior
Right suprarenal gland abdominal wall, forming the right paracolic gutter between the antero-
lateral abdominal wall and the ascending colon.
Right subhepatic space
Lesser omentum
Right kidney The lesser omentum is formed by two layers of peritoneum separated
by a variable amount of connective tissue and fat. It is derived from the
Second part of the
ventral mesogastrium. It runs between the inferior visceral surface of
duodenum
the liver and the abdominal oesophagus, stomach, pylorus and first part
of the duodenum. Superiorly, its attachment to the inferior surface of
Right end of transverse
the liver forms an L shape. The vertical component of the L is formed
mesocolon
by the fissure for the ligamentum venosum; inferiorly, the attachment
turns horizontally to complete the L in the porta hepatis. The part of
the lesser omentum running between the liver and the stomach is
Right end of
known as the gastrohepatic ligament and the part between the liver and
transverse colon
duodenum is the hepatoduodenal ligament. The right and left gastric
vessels, branches of the vagus nerves and lymph nodes are contained
within the two layers of the gastrohepatic ligament close to its gastric
attachment. An accessory or replaced left hepatic artery is sometimes
present (p. 1166). The anterior layer of the lesser omentum descends
from the fissure for the ligamentum venosum on to the anterior surface
of the abdominal oesophagus, stomach and duodenum. The posterior
layer descends from the fissure and runs on to the posterior surface of
Fig. 63.3 A sagittal section through the abdomen to the right of the the stomach and pylorus. At the lesser curvature of the stomach, the
epiploic foramen along the line of W–W in Figure 63.2. peritoneal layers of the lesser omentum split to enclose the stomach
Fig. 63.4 A section through the upper part of
the abdominal cavity, along the line X–X in
Figure 63.2. The boundaries of the epiploic
foramen are shown and a small recess of the
Liver lesser sac is displayed anterior to the head
of the pancreas. Note that the transverse
colon and its mesocolon are adherent to the
posterior two layers of the greater omentum.
Four peritoneal layers contribute to the
formation of the greater omentum because
Accessory hepatic vein
the apron of omentum is folded back on
itself.
Right branch of hepatic artery
Epiploic foramen
Bile duct
Duodenum, first part
Inferior vena cava
Head of pancreas
Transverse mesocolon,
adherent to greater omentum
Transverse colon
Greater omentum
Duodenum, third part
Superior mesenteric vein | 1,525 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Fig. 63.5 A sagittal section through the
abdomen, approximately in the median
plane. Compare with Figure 63.2. The section
cuts the posterior abdominal wall along the
line Y–Y in Figure 63.2. The peritoneum is
shown in blue except along its cut edges,
which are left white.
Lesser omentum in fissure
for ligamentum venosum
Caudate lobe of liver
Lesser omentum
Lesser sac
Hepatic artery
Neck of pancreas
Antrum of stomach
Superior mesenteric artery
Uncinate process of head of pancreas
Duodenum, third part
Transverse mesocolon, adherent to
posterior layers of greater omentum
Transverse colon
Mesentery of the small intestine
Greater omentum
and are continuous with the visceral peritoneum covering the anterior sheet and is attached to the greater curve of the stomach (see Fig. 63.5);
and posterior surfaces of the stomach. The posterior layer of the lesser this supracolic part of the greater omentum is known as the gastrocolic
omentum forms part of the anterior surface of the lesser sac (see ligament. The most anterior layer of peritoneum of the greater omentum
Fig. 63.5). is continuous with the visceral peritoneum over the anterior surface of
The free right lateral border of the lesser omentum is thickened and the stomach and duodenum. The anterior sheet descends from the
extends from the porta hepatis to the junction between the first and greater curvature of the stomach and first part of the duodenum for a
second parts of the duodenum. This free border forms the anterior variable distance into the peritoneal cavity and then turns sharply back-
boundary of the epiploic foramen and contains the portal vein (poste- wards on itself to ascend as the posterior sheet. The posterior sheet
riorly), the bile duct (anteriorly to the right), and hepatic artery proper passes anterior to the transverse colon and transverse mesocolon, and
(anteriorly to the left) (see Fig. 63.6B), together with lymphatics, lymph is attached to the posterior abdominal wall above the origin of the
nodes and hepatic autonomic nerves. An accessory or replaced right transverse mesocolon and anterior to the head and body of the pancreas
hepatic artery arising from the superior mesenteric artery may some- (see Figs 63.2, 63.5). The anterior peritoneal layer of the posterior sheet
times be found in the free edge of the lesser omentum, usually running is continuous with the peritoneum of the posterior wall of the lesser
posterior to the portal vein. Occasionally, the free margin of the lesser sac. The posterior peritoneal layer is reflected sharply inferiorly and is
omentum extends to the right and runs on to the gallbladder, when it continuous with the anterior layer of the transverse mesocolon. The
is referred to as the cystoduodenal ligament (Ashaolu et al 2011). posterior sheet is adherent to the transverse colon and its mesentery. In
The upper border of the lesser omentum is short and runs over the early fetal life, the greater omentum and transverse mesocolon are sepa-
inferior surface of the diaphragm between the liver and medial aspect rate structures, and this arrangement occasionally persists. During
of the abdominal oesophagus. The lesser omentum is thinner in this surgery, the natural adhesions between the transverse mesocolon and
region and may be fenestrated or incomplete; variations in thickness greater omentum can be divided, and the greater omentum can be
are dependent on the amount of connective tissue, especially fat. detached from the transverse colon and mesocolon if required. Access
into the lesser sac can then be obtained by dividing the upper part of
the posterior sheet of greater omentum. This gives a relatively bloodless
Greater omentum
surgical approach to the posterior wall of the stomach and the anterior
surface of the pancreas.
The greater omentum is the largest peritoneal fold and hangs inferiorly On the left side of the abdomen, the greater omentum is continuous
from the greater curvature of the stomach. When the undisturbed with the gastrosplenic ligament; on the right side, it extends to the
abdomen is opened, the greater omentum is frequently draped over the beginning of the duodenum (see Fig. 63.2). A fold of peritoneum, the
upper abdominal organs, but often not in the even distribution shown hepatocolic ligament, may run from either the inferior surface of
in many illustrations. It is usually thin but always contains some the right lobe of the liver or the first part of the duodenum to the right
adipose tissue and is a common site for storage of fat in obese individu- side of the greater omentum or hepatic flexure of the colon. The right
als, particularly males (Coulier 2009). The greater omentum is a double border of the greater omentum is usually adherent to the anterior
sheet: each sheet consists of two layers of peritoneum separated by surface of the hepatic flexure and upper ascending colon but its perito-
a scant amount of connective tissue. The two sheets are folded back neal layers are not continuous with the visceral peritoneum over this
on themselves and firmly adherent to each other below the transverse part of the colon. The right border of the greater omentum may also be
colon. Above this level the anterior sheet separates from the posterior attached to a thin but vascular peritoneal band (Jackson’s membrane), | 1,526 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
General arrangement of the peritoneum
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A
Falciform ligament Left anterior perihepatic space
Left posterior perihepatic space
Right lobe of liver
Upper limit of lesser omentum
Superior recess of lesser sac
Fundus of stomach
Right subphrenic space
Aorta Left anterior subphrenic space
Inferior vena cava Spleen
Bare area of liver
Left posterior subphrenic space
Right inferior pleural recess
Inferior lobe of left lung
B
Falciform ligament
Hepatic artery
Stomach
Free border of the lesser omentum
Left gastroepiploic artery
within gastrosplenic ligament
Right lobe of liver
Gallbladder
Spleen
Common bile duct
Portal vein
Splenic artery within
splenorenal ligament
Epiploic foramen
Inferior vena cava Superior recess of lesser sac
Aorta Left suprarenal gland
C
Pylorus
Falciform ligament
Right lobe of liver
Stomach
Gallbladder
Gastroduodenal artery Lesser sac
Neck of pancreas
Transverse mesocolon
Head of pancreas
Transverse colon
Common bile duct
Left end of greater omentum
Portal vein
Descending colon
Inferior vena cava
Body of pancreas
Aorta
Fig. 63.6 Transverse sections through the abdomen. A, At the level of the line A–A in Figure 63.2. The line passes through the bare area of the liver at
the superior end of the lesser omentum. The parts of the left subphrenic space are clearly seen, although they are continuous with each other. B, At the
level of line B–B in Figure 63.2, viewed from below. The peritoneal cavity is shown by blue shading; the peritoneum and its cut edges are in pale blue.
C, A transverse section through the abdomen at the level of the line C–C in Figure 63.2, viewed from below. Colours as in Figure 63.2. | 1,527 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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which, when present, runs from the anterior aspect of the ascending extends from the splenic flexure of the colon to the diaphragm at about
colon and caecum to the posterolateral abdominal wall. Other perito- the level of the eleventh rib. Inferiorly, it is continuous with the perito-
neal folds between the ascending colon and posterolateral abdominal neum of the lateral end of the transverse mesocolon near the tip of the
wall in the right lateral paracolic gutter are occasionally present. Less pancreatic tail, and the splenorenal ligament at the hilum of the spleen.
commonly, the left border of the greater omentum is adherent to the Undue traction on the peritoneal attachments of the spleen at
anterior surface of the descending colon. surgery may cause a capsular tear and serious bleeding. Downward trac-
The greater omentum has a rich blood supply derived from the right tion on the phrenicocolic ligament during mobilization of the splenic
and left gastroepiploic vessels that run between the two peritoneal flexure is particularly hazardous; medial traction on the greater
layers of the anterior sheet of greater omentum, close to the greater omentum may also injure the spleen if the omentum is adherent to the
curvature of the stomach. These vessels give off numerous omental splenic capsule.
(epiploic) branches that run the length of the omentum. Microscopic
capillary convolutions, sometimes termed ‘omental glomeruli’, lie
directly beneath the mesothelium of the greater omentum. They are PERITONEUM OF THE LOWER ABDOMEN
surrounded by aggregations of macrophages and lymphocytes (milky
spots) that drain into lymphatic channels (Shimotsuma et al 1993); the The posterior surface of the lower anterior abdominal wall is lined by
macrophages form clusters near the mesothelial surface, while B and T parietal peritoneum, which extends from the linea alba centrally to the
lymphocytes are grouped around vessels. The fenestrated endothelium lateral paracolic gutters, where it is reflected over the front and sides of
lining the omental glomeruli and the mesothelium overlying the milky the ascending colon on the right and the descending colon on the left
spots share a similar mesodermal origin and together they form sites (see Fig. 63.2). Occasionally, the ascending and descending colon are
of leukocyte migration and peritoneal fluid absorption (Platell et al suspended by a short mesentery from the posterior abdominal wall
2000). The number and size of milky spots increase in the presence of (Ch. 66). Between the ascending and descending colon, the peritoneum
peritoneal inflammation, highlighting their defensive role. covers the posterior abdominal wall, except where it is reflected over
The greater omentum serves several important functions. It is highly the oblique root of the mesentery of the small intestine. Over the pos-
mobile and frequently becomes adherent to inflamed viscera or foreign terior abdominal wall, it covers psoas major and quadratus lumborum,
bodies within the abdominal cavity. This can limit the spread of infec- the inferior vena cava, duodenum, vertebral column and both ureters.
tion, as in the walling off of acute appendicitis, and promote haemo- In the upper abdomen, the posterior parietal peritoneum is reflected
stasis. However, it may also block peritoneal drains and catheters (such anteriorly where it is continuous with the peritoneum of the posterior
that omentectomy is sometimes performed when placing some intra- layer of the transverse mesocolon.
peritoneal catheters). It absorbs peritoneal fluid. It contains macro-
phages and lymphoid tissue capable of destroying pathogens; Transverse mesocolon
macrophages and neutrophils readily migrate from the greater omentum
into the peritoneal cavity in the presence of peritonitis. It promotes
The mesentery of the transverse colon is a broad fold of visceral peri-
neovascularization of structures to which it becomes adherent and thus
toneum reflected anteriorly from the posterior abdominal wall. It sus-
promotes healing of ischaemic tissues and supports splenic autotrans-
pends the transverse colon in the peritoneal cavity. The root of the
plantation (Ch. 70). It is rarely the site of primary pathology; reports
transverse mesocolon passes obliquely from the anterior aspect of the
of segmental infarction, torsion or other disorders are rare.
second part of the duodenum, over the head and neck of the pancreas,
The remarkable capacity of the greater omentum to participate in
superior to the duodenojejunal junction over the upper pole of the left
reparative processes is highlighted by its use as an omental pedicle flap
kidney to the splenic flexure (see Fig. 63.2). It varies considerably in
or free flap in reconstructive surgery. It has been used to close gastroin-
length but is shortest at either end. It contains the middle colic vessels
testinal perforations, fill ‘dead space’ after surgical excision of pathol-
and their branches, together with autonomic nerves from the aortic
ogy, and cover wound defects. A greater omental pedicle or free flap
plexus, lymphatics and lymph nodes. Near the splenic flexure, the
based on the right gastroepiploic vessels may be mobilized by dividing
ascending branch of the left colic artery terminates within the transverse
the gastric branches of these vessels close to the surface of the stomach
mesocolon. Its two peritoneal layers pass to the posterior surface of the
and the left gastroepiploic vessels near their origin.
transverse colon, where they separate to invest the colon. The upper
layer of peritoneum is continuous with the posterior layer of the greater
Peritoneal connections of the spleen omentum, to which it is adherent (see Fig. 63.5). The lower layer of
peritoneum of the transverse mesocolon is continuous with the perito-
neum of the posterior abdominal wall. Lateral extensions of the trans-
The peritoneal connections of the spleen anchor it in the left upper
verse mesocolon produce two folds: on the right, the duodenocolic
quadrant of the abdomen; they include the gastrosplenic, splenorenal
ligament extends from the transverse mesocolon at the hepatic flexure
and phrenicocolic ligaments. The gastrosplenic ligament runs between
to the second part of the duodenum; on the left, the phrenicocolic liga-
the greater curvature of the stomach and the hilum of the spleen, and
ment extends from the transverse mesocolon at the splenic flexure to
is in continuity with the left side of the greater omentum. The peritoneal
the diaphragm. The root of the transverse mesocolon is closely related
layers of the gastrosplenic ligament separate to enclose the spleen and
to the upper limit of the root of the mesentery of the small intestine
then rejoin to form the splenorenal and phrenicocolic ligaments. The
near the uncinate process of the pancreas.
splenorenal ligament extends from the spleen to the posterior abdomi-
nal wall, and the phrenicocolic ligament connects the splenic flexure of
Mesentery of the small intestine
the colon to the diaphragm.
The splenorenal ligament is formed from two layers of peritoneum
(see Fig. 63.6B). The anterior layer is continuous medially with the The mesentery of the small intestine is arranged as a complex fan that
peritoneum of the posterior wall of the lesser sac over the left kidney is formed from two layers of peritoneum (anterosuperior and postero-
and runs up to the splenic hilum, where it is continuous with the pos- inferior) separated by fatty connective tissue containing vessels and
terior layer of the gastrosplenic ligament. The posterior layer of the nerves. The root of the mesentery lies along a line running diagonally
splenorenal ligament is continuous laterally with the peritoneum over from the duodenojejunal flexure on the left side of the second lumbar
the inferior surface of the diaphragm and runs on to the splenic surface vertebral body to the right sacroiliac joint (see Fig. 63.2). The root
over the renal impression. The splenic vessels lie between the layers of crosses over the third part of the duodenum, abdominal aorta, inferior
the splenorenal ligament, and the tail of the pancreas is usually present vena cava, right ureter and right psoas major. The average length of the
in its lower portion. root of the mesentery is 15 cm in adults while along its intestinal
The gastrosplenic ligament is also formed from two layers of perito- attachment it measures the same length as the small intestine (approxi-
neum (see Fig. 63.6B). The posterior layer is continuous with the peri- mately 5 m). Consequently, the mesentery is usually thrown into mul-
toneum of the splenic hilum and the peritoneum over the posterior tiple folds along its intestinal border. The average depth of the mesentery
surface of the stomach. The anterior layer is continuous with the peri- from the root to the intestinal border is 20 cm, but this varies along the
toneum reflected off the gastric impression of the spleen and with the length of the small intestine: it is shortest at the jejunum and terminal
peritoneum over the anterior surface of the stomach. The short gastric ileum, and longest in the mid-ileal region. Its two peritoneal layers
and left gastroepiploic branches of the splenic artery, with their corre- contain the jejunal and ileal branches of the superior mesenteric vessels,
sponding veins, pass between the layers of the gastrosplenic ligament. nerves related to the superior mesenteric plexus, lymphatics and
A fan-shaped fold of peritoneum often extends from the anterior aspect regional lymph nodes. The length and mobility of the mesentery may
of the gastrosplenic ligament below the inferior pole of the spleen and make it difficult to determine the site and orientation of a loop of small
blends with the phrenicocolic ligament. The phrenicocolic ligament intestine through a small surgical incision. Tracing the continuity of a | 1,528 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
General arrangement of the peritoneum
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peritoneal layer of the mesentery on to the posterior abdominal wall
may be useful in orientating an isolated loop if the duodenojejunal Umbilicus
flexure or ileocaecal junction is not readily accessible. The mesentery of Posterior
the small intestine is sometimes joined to the transverse mesocolon at layer of
the duodenojejunal flexure by a peritoneal band. Occasionally, the rectus
fourth part of the duodenum possesses a very short mesentery that is sheath
continuous with the upper end of the root of the mesentery of the small Arcuate
intestine. Additional bands of peritoneum may connect the terminal line
ileum to the posterior abdominal wall. The root of the mesentery of Inferior
the small intestine is continuous with the peritoneum that surrounds epigastric
the appendix and caecum in the right iliac fossa. vessels
Testicular
Mesoappendix vessels
The mesentery of the appendix is a fatty, triangular fold of peritoneum External iliac
that passes between the posterior surface of the mesentery of the termi- artery and vein
nal ileum close to the ileocaecal junction and the vermiform appendix. Lateral
It may end short of the tip of the appendix, in which case a thin, shallow inguinal
fold of peritoneum containing fat is present towards the tip. It encloses fossa Medial
the blood vessels, nerves and lymph vessels of the vermiform appendix, umbilical fold
and usually contains a lymph node. A small fold of peritoneum runs Median
Medial
between the terminal ileum and the anterior layer of the mesoappendix inguinal fossa umbilical fold
(the ‘bloodless fold of Treves’), and another fold of peritoneum con-
Supravesical fossa Ureter
taining the anterior caecal artery may extend from the terminal ileal
mesentery to the anterior wall of the caecum (see below). Urinary bladder Vas deferens
Fig. 63.7 The infra-umbilical part of the anterior abdominal wall of a male
Sigmoid mesocolon subject: posterior surface, with the peritoneum in situ.
The sigmoid mesocolon varies in length and depth between individuals.
The root of the sigmoid colon usually has a shallow, inverted V-shaped orly from the anterior surface of the rectum over the upper poles of
attachment; the apex of the V overlies the division of the left common the seminal vesicles and on to the posterior surface of the bladder,
iliac artery (see Fig. 63.2). Alternatively, the attachment may form a producing the rectovesical pouch. The pouch is limited laterally by
gentle curve. The left limb of the attachment runs over the left psoas sacrogenital folds of peritoneum, which extend posteriorly from the
major and along the external iliac vessels. The right limb passes over sides of the bladder to the anterior aspect of the sacrum. The perito-
the pelvic brim towards the midline at the level of the third sacral ver- neum covering the posterosuperior surface of the bladder forms a para-
tebra. The anteromedial peritoneal layer of the sigmoid mesocolon is vesical fossa on each side that is limited laterally by a ridge of peritoneum
continuous with the peritoneum of the lower left posterior abdominal containing the vas deferens; the depth of the paravesical fossae depends
wall, and its posterolateral layer is continuous with the peritoneum of on the volume of urine in the bladder. When the bladder is empty, a
the lateral abdominal wall. Bands of peritoneum may be present transverse vesical fold may be visible at laparoscopy; its medial portion
running from the proximal sigmoid colon to the posterior abdominal overlies the superior vesical artery or arteries (Boaz et al 2011). Between
wall. The sigmoid and superior rectal vessels run between its layers and the paravesical and pararectal fossae, the ureters and internal iliac
the left ureter descends into the pelvis behind its apex and anterior to vessels may cause slight elevations in the peritoneum. From the apex
the bifurcation of the left common iliac artery. of the bladder, the median umbilical fold extends superiorly on the
posterior surface of the lower anterior abdominal wall to the umbilicus.
Peritoneum of the lower anterior When the bladder distends, the overlying peritoneum is lifted so that
part of the anterior surface of the bladder comes into direct contact with
abdominal wall
the posterior surface of the lower anterior abdominal wall. This means
that a distended bladder can be punctured directly through the lower
The peritoneum of the lower anterior abdominal wall is raised into five anterior abdominal wall without traversing the peritoneal cavity
folds (sometimes referred to as ‘ligaments’), which diverge as they (suprapubic puncture).
descend from the umbilicus. They are the median, right and left medial,
and right and left lateral, umbilical folds (Fig. 63.7, see Fig. 75.9). The Peritoneum of the female pelvis
median umbilical fold extends from the umbilicus to the apex of the
bladder and contains the urachus or its remnant (Ch. 72). The medial
In females, peritoneum covers the anterolateral surface of the upper
umbilical fold overlies the obliterated umbilical artery, which ascends
rectum as it does in the male, but it descends further over the anterior
from the internal iliac artery in the pelvis to the umbilicus. The lateral
surface of the rectum. The pararectal and paravesical fossae are limited
umbilical fold covers the inferior epigastric vessels below their entry
laterally by the peritoneum that covers the uterosacral and round liga-
into the rectus sheath. The supravesical fossa lies between the medial
ments of the uterus, respectively (see Figs 77.14, 77.15, 77.18). The
and median umbilical folds on each side of the midline, and the medial
presence of the uterus and vagina means that there are two pelvic
and lateral inguinal fossae lie on either side of each lateral umbilical
pouches instead of the single rectovesical pouch seen in males. The
fold. The lateral inguinal fossa overlies the deep inguinal ring, and the
peritoneum from the rectum is reflected anteriorly on to the posterior
medial inguinal fossa overlies the femoral ring (Healy and Reznek
surface of the posterior fornix of the vagina and the uterus, forming the
1999).
recto-uterine pouch (of Douglas). The depth of the pouch – namely,
the extent to which it descends on the posterior surface of the vagina
– is variable (Baessler and Schuessler 2000). The peritoneum covers the
PERITONEUM OF THE PELVIS
fundus and body of the uterus, descending on its anterior surface as far
as the junction of the body and cervix; from here, it is reflected forwards
The parietal peritoneum of the abdominal wall is continuous with the
on to the posterosuperior surface of the bladder, forming a shallow
parietal peritoneum that lines the side walls of the pelvis. The arrange-
vesico-uterine pouch. As in males, the peritoneum over the dome of the
ment of the pelvic visceral peritoneum differs between the sexes.
bladder is reflected on to the posterior surface of the lower anterior
abdominal wall. Recto-uterine folds containing the uterosacral liga-
Peritoneum of the male pelvis
ments pass posteriorly from the sides of the cervix to the sacrum,
running lateral to the rectum. Peritoneum is also reflected from the
In males, the peritoneum of the left lower abdominal wall is reflected anterior and posterior uterine surfaces to the lateral pelvic walls as the
from the distal sigmoid colon and anterolateral surface of the upper broad ligament of the uterus (see Fig. 77.18). This consists of anterior
rectum to the side walls of the true pelvis, where it forms the right and and posterior layers that are continuous at the upper border of the liga-
left pararectal fossae (Fig. 63.8); these vary in size according to the ment. The broad ligament contains the uterine tubes in its free upper
degree of distension of the rectum. The peritoneum is reflected anteri- border; the ovaries are suspended from its posterior layer. Inferiorly, the | 1,529 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
PERiTonEum And PERiTonEAl CAviTy
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noiTCES
Sacrum
Internal iliac vein
Sigmoid colon
Internal iliac artery
Rectum
External iliac vein
External iliac artery Pararectal fossa
Sacrogenital fold
Ureter
Rectovesical pouch
Ilium
Bladder Vas deferens
Transverse vesical fold
Paravesical fossa
Median umbilical fold Medial umbilical fold
Inferior epigastric vessels
Rectus abdominis
Fig. 63.8 The peritoneum of the male pelvis: anterosuperior view.
peritoneum at the base of the broad ligament merges with the pelvic the foregut is felt in the epigastric region, that from midgut structures
parietal peritoneum. The ovarian fossa is a shallow depression in the in the umbilical region, and that from hindgut structures in the
peritoneal lining of the lateral pelvic wall between the peritoneal ridges suprapubic region; none of these sensations is significantly lateralized.
formed by the obliterated umbilical arteries anteriorly, the ureter pos- Pain from the pancreas, gallbladder and even the small bowel may
teriorly, and the external iliac vessels above; it lies behind the lateral radiate to the back. Stretch or irritation of the visceral peritoneum
attachment of the broad ligament and usually contains the ovary in may also elicit profound reflex vasomotor and cardiac changes medi-
nulliparous females. ated by autonomic nerves, including a vasovagal response. This is of
considerable clinical relevance. Painful responses to manipulation of
the parietal peritoneum may be abolished by local or regional anaes-
VASCULAR SUPPLY AND LYMPHATIC DRAINAGE thesia. In marked contrast, the direct central connections of visceral
afferents, particularly via the vagus nerve, mean that stretching the
Parietal and visceral peritoneum develops from the somatopleural visceral peritoneum may induce profound effects, including acute
and splanchnopleural layers, respectively, of the lateral plate mesoderm haemodynamic instability, despite local or regional (including spinal)
(p. 1059). Parietal peritoneum is supplied by the somatic blood vessels anaesthesia.
of the abdominal and pelvic walls, and its lymphatics join those in the
body wall and drain to parietal lymph nodes. Visceral peritoneum is
best considered as an integral part of the viscus it covers: its blood
GENERAL ARRANGEMENT OF THE
supply and lymphatic drainage therefore correspond to those of the
associated viscus. PERITONEAL CAVITY
The peritoneal cavity is a single continuous space between the parietal
INNERVATION
peritoneum lining the abdominal wall and the visceral peritoneum
enveloping the abdominal organs. It consists of the greater sac, which
The parietal peritoneum is innervated by somatic efferent and afferent is the main peritoneal cavity surrounding most of the abdominal and
nerves that also supply the muscles and skin of the overlying body wall. pelvic viscera, and the lesser sac, or omental bursa, which is a small
The visceral peritoneum is innervated by afferent nerves that travel with diverticulum situated behind the stomach and lesser omentum and in
the autonomic supply to the underlying viscera. Sensations arising from front of the pancreas. These two sacs communicate via the epiploic
pathologies that affect the parietal or visceral peritoneum reflect these foramen.
different patterns of innervation. Well-localized pain is elicited by For clinical purposes, the peritoneal cavity can be divided into
mechanical, thermal or chemical stimulation of nociceptors in the pari- several ‘spaces’; pathological processes are often contained within these
etal peritoneum; the pain is usually well localized to the affected region. spaces and their anatomy may influence diagnosis and treatment. It is
Somatic nerves that innervate the parietal peritoneum also supply the useful to divide the peritoneal cavity into two main compartments,
corresponding segmental skin and muscles; when the parietal perito- supramesocolic (often simply called supracolic) and inframesocolic (or
neum is irritated, local reflex muscle contraction occurs, resulting in infracolic), which are partially separated by the transverse colon and its
clinical signs of guarding or even rigidity of the abdominal wall. The mesentery. The pelvic peritoneal spaces are described above.
parietal diaphragmatic peritoneum is supplied centrally by afferent
fibres from the phrenic nerves and peripherally by the lower intercostal
and subcostal nerves; peripheral irritation of the diaphragm may there-
fore result in pain localized in the distribution of the lower thoracic SUPRAMESOCOLIC COMPARTMENT
spinal nerves, while central irritation causes referred pain in the cutane-
ous distribution of the third to fifth cervical spinal nerves (the shoulder This lies between the diaphragm and the transverse mesocolon. It can
region). The innervation of the parietal peritoneum of the true pelvis be arbitrarily divided into right and left supramesocolic spaces. The
is poorly documented but the obturator nerve makes a significant right supramesocolic space can be subdivided into the right subphrenic
contribution. space, the right subhepatic space and the lesser sac. The left suprameso-
Irritation or stretch of the visceral peritoneum causes poorly local- colic space can be divided into two subspaces: the left subphrenic space
ized discomfort. The sensation of pain is referred to a diffuse area of and the left perihepatic space. These ‘spaces’ usually communicate but
the abdominal wall. Thus, discomfort from structures derived from may nevertheless be sites of localized fluid collections. | 1,530 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
General arrangement of the peritoneal cavity
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RETPAHC
Right subphrenic space the posterior aspect of the fundus of the stomach and forms part of the
upper left border of the lesser sac. The two layers of the gastrophrenic
ligament diverge near the abdominal oesophagus, leaving part of the
The right subphrenic space lies between the diaphragm and the anterior,
posterior gastric surface devoid of peritoneum. The left gastric artery
superior and right lateral surfaces of the right lobe of the liver. It is
runs forwards here into the lesser omentum.
bounded on the left by the falciform ligament and posteriorly by the
The lesser sac is indented by a crescentic peritoneal fold that runs
upper layer of the coronary ligament (see Fig. 63.3). Because of the
from the upper border of the neck of the pancreas to the upper part of
clockwise flow of peritoneal fluid from the lower abdomen and pelvis,
the lesser curvature of the stomach. It is variably described but com-
it is a relatively common site for an infected fluid collection after a
monly known as the gastropancreatic fold. The upper part of this fold
perforated appendicitis or duodenal ulcer.
overlies the left gastric artery as it runs from the posterior abdominal
wall to the lesser curvature of the stomach. The lower part of the fold
Right subhepatic space (hepatorenal pouch)
overlies the common hepatic artery as it runs from the posterior abdom-
inal wall to the lesser omentum. When the fold is prominent, it divides
The right subhepatic space lies between the inferior surface of the right
the lesser sac into a smaller superior and a larger inferior recess. The
lobe of the liver and the upper pole of the right kidney. It is bounded
superior recess lies posterior to the lesser omentum and encloses
superiorly by the inferior layer of the coronary ligament, laterally by the
the caudate lobe of the liver; it extends superiorly into the fissure for
right lateral abdominal wall, posteriorly by the anterior surface of the
the ligamentum venosum and lies adjacent to the right crus of the
upper pole of the right kidney, and inferomedially by the hepatic
diaphragm posteriorly. The inferior recess of the lesser sac lies between
flexure, transverse mesocolon, second part of the duodenum, and part
the stomach and pancreas, and is contained within the double sheet of
of the head of the pancreas. In the supine position, the hepatorenal
the greater omentum.
pouch (of Morison) is more dependent than the right paracolic gutter.
Acute pancreatitis is probably the most common cause of a fluid
It is a site where a pathological fluid collection may develop.
collection within the lesser sac (or just behind its posterior peritoneal
lining) (p. 1182). Bleeding from trauma or a ruptured splenic artery
Lesser sac (omental bursa)
aneurysm and perforation of a posterior gastric ulcer are other causes
of lesser sac collections.
The lesser sac is a cavity lined with peritoneum and connected to the
Epiploic foramen
main peritoneal cavity (greater sac) by the epiploic foramen (of
Winslow). It is considered part of the right supramesocolic compart- The epiploic foramen (foramen of Winslow or aditus to the lesser sac)
ment because it develops in the embryo on the right side of the ventral is a short, vertical slit, about 3 cm in height in adults, behind the free
mesogastrium (p. 1059). It has posterior and anterior walls and superior, right border of the lesser omentum. It is the entrance to the lesser sac
inferior, right and left borders. The sac varies in size according to the from the greater sac. The hepatoduodenal ligament, formed by the
volume of the viscera making up its walls; it may be partially obliterated thickened free right margin of the lesser omentum and extending
by natural adhesions between the anterior and posterior walls. between the porta hepatis above and the upper border of the first part
The anterior wall of the lesser sac consists of the posterior peritoneal of the duodenum below, forms the anterior boundary of the foramen.
layer of the lesser omentum, the peritoneum over the posterior wall of Within this free border lie the bile duct (anteriorly on the right), the
the stomach and first part of the duodenum, and the posterior upper hepatic artery (anteriorly on the left) and the portal vein (posteriorly),
part of the anterior sheet of the greater omentum (see Fig. 63.5). At its together with nerves and lymphatics (see above). Rapid control of the
right border, the anterior wall is mostly formed by the lesser omentum hepatic artery and portal vein can be obtained by compression of the
but, towards the left, the lesser omentum becomes progressively shorter free edge of the lesser omentum (a ‘Pringle’ manœuvre), which is a
and more of the anterior wall is formed by the posterior surface of the potentially useful technique in liver trauma and surgery. Superiorly, the
stomach and greater omentum. peritoneum of the posterior layer of the hepatoduodenal ligament runs
The lower part of the posterior wall of the lesser sac is formed by the over the caudate process of the liver, forming the roof of the epiploic
anterior peritoneal layer of the posterior sheet of the greater omentum, foramen. This layer of peritoneum is then reflected on to the inferior
which overlies the transverse mesocolon. More superiorly, the perito- vena cava, which forms the posterior border of the foramen. The floor
neum of the posterior wall covers, from below upwards, a small part of of the foramen is formed by the peritoneal reflection overlying the
the head and the whole neck and body of the pancreas, the medial part upper border of the first part of the duodenum as it runs forwards above
of the anterior aspect of the upper pole of the left kidney, most of the the head of the pancreas. A narrow passage, the vestibule of the lesser
left suprarenal gland, the commencement of the abdominal aorta, the sac, may be formed to the left of the foramen between the caudate
coeliac trunk and part of the diaphragm (see Fig. 63.2). The inferior process above and the first part of the duodenum below. To the right,
phrenic, splenic, left gastric and common hepatic arteries lie partly the rim of the foramen is continuous with the peritoneum of the greater
behind the bursa. Many of these structures form the ‘bed’ of the stomach sac. The anterior and posterior walls of the foramen are normally
and are separated from it only by the linings of the lesser sac. apposed, which partly explains why patients can develop large fluid
The superior border of the lesser sac is narrow and lies between the collections isolated to the greater or lesser sac (Shrestha et al 2010).
right side of the oesophagus and the upper end of the fissure for the
Left subphrenic space
ligamentum venosum; it is sometimes referred to as the superior recess
of the omental bursa. Here, the peritoneum of the posterior wall of the
lesser sac is reflected anteriorly from the diaphragm to join the posterior The left subphrenic space lies between the diaphragm, the anterior and
layer of the lesser omentum. The inferior border runs along the line of superior surfaces of the left lobe of the liver, the anterosuperior surface
fusion of the layers of the greater omentum, which extends from the of the stomach and the diaphragmatic surface of the spleen. To the right
gastrosplenic ligament on the left to the peritoneal fold behind the first it is bounded by the falciform ligament. It is expanded in the absence
part of the duodenum on the right. If the layers of the greater omentum of the spleen and is a common site for fluid collection after splenec-
are not completely fused, the lesser sac may extend to the inferior limit tomy. The left subphrenic space is substantially larger than the right and
of this structure, but this is rarely demonstrable at surgery. can be divided into a left perihepatic space and anterior and posterior
The right border of the lesser sac is where the peritoneum overlying subphrenic spaces (see Fig. 63.6); these are in continuity in the absence
the head and neck of the pancreas is reflected on to the inferior aspect of disease. The definitions of the boundaries of these spaces vary.
of the first part of the duodenum. The line of this reflection ascends to The left anterior subphrenic space is large and lies between the
the left, along the medial side of the gastroduodenal artery. Near the superior and anterolateral surfaces of the spleen and the diaphragm.
upper duodenal border, the right border joins the floor of the epiploic Inferiorly and medially, this space is bounded by the phrenicocolic,
foramen round the hepatic artery proper. The epiploic foramen there- splenorenal and gastrosplenic ligaments. The phrenicocolic ligament
fore interrupts the right border. Above the epiploic foramen, the right partially obstructs the flow of fluid from the left paracolic gutter (Meyers
border is formed by the peritoneal reflection from the diaphragm to the 1973), which may explain why left subphrenic collections are less fre-
right margin of the caudate lobe of the liver, which then crosses the quent than right subphrenic collections after lower abdominal and
inferior vena cava. The left border of the lesser sac runs from the left pelvic surgery. Nevertheless, the left subphrenic space is a relatively
end of the root of the transverse mesocolon and is mostly formed by common site of fluid collection after upper abdominal surgery, particu-
the inner peritoneal layers of the splenorenal and gastrosplenic liga- larly surgery involving the spleen or distal pancreas. The left posterior
ments (see Fig. 63.6). The part of the lesser sac lying between the subphrenic space is small and lies between the fundus of the stomach
splenorenal and gastrosplenic ligaments is referred to as the splenic and the diaphragm above the origin of the splenorenal ligament.
recess. Above the spleen, the two ligaments merge to form the short The left perihepatic space is sometimes subdivided into anterior and
gastrophrenic ligament, which passes forwards from the diaphragm to posterior spaces. The left anterior perihepatic space lies between the | 1,531 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Peritoneum and peritoneal cavity
1107.e1
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RETPAHC
Free tumour cells in the peritoneal cavity, especially from mucinous
tumours, may gain access to the lesser sac and settle by gravity into the
inferior recess of the lesser sac. This is more likely on the right side of
the lesser sac in an area recognized surgically as the ‘subpyloric space’.
Growth of tumour at this site may cause gastric outlet obstruction.
During surgical exploration of the abdomen, some peritoneal sur-
faces cannot be visualized without the aid of specific surgical manœu-
vres. One of these sites is the posterior aspect of the hepatoduodenal
ligament. The recess created by the posterior aspect of the hepatoduo-
denal ligament and the caudate process is an important site for muci-
nous peritoneal metastases. It can be visualized during cytoreductive
surgery by passing a tape around the structures in the free edge of the
lesser omentum and retracting them forwards. | 1,532 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
PERiTonEum And PERiTonEAl CAviTy
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anterosuperior surface of the left lobe of the liver and diaphragm. The
Transverse
left posterior perihepatic space, also known as the gastrohepatic recess, mesocolon
lies inferior to the left lobe of the liver. It extends into the fissure for
the ligamentum venosum on the right. Posteriorly, it is separated from Inferior
mesenteric vein
the superior recess of the lesser sac by the lesser omentum.
Superior
Extraperitoneal subphrenic spaces duodenal fold
Superior
There are two potential subphrenic spaces that actually lie outside the
duodenal recess
peritoneum but are of clinical relevance because they may be sites of
fluid accumulation. The right extraperitoneal space is bounded by the Inferior
two layers of the coronary ligament, the bare area of the liver, and the duodenal recess
inferior surface of the right hemidiaphragm. The left extraperitoneal Inferior
space lies anterior to the left suprarenal gland and upper pole of the duodenal fold
left kidney. Left colic artery
Fig. 63.9 The superior and inferior duodenal recesses. Note that the
INFRAMESOCOLIC COMPARTMENT
transverse colon and jejunum have been displaced.
The inframesocolic compartment (also called the infracolic compart-
ment) lies below the transverse mesocolon and transverse colon, and
is divided into two unequal spaces by the root of the mesentery of the
a fossa or recess, the bowel may become obstructed or strangulate from
small intestine (see Fig. 63.2). It contains the right and left paracolic
a constriction at the entrance to the recess. The contents of the perito-
gutters lateral to the ascending and descending colon, respectively.
neal fold forming the fossa/recess must be considered when repairing
As a consequence of the mobility of the transverse mesocolon and
such a hernia.
mesentery of the small intestine, and the open boundaries of the
inframesocolic compartment, disease processes are rarely confined to
Lesser sac
the compartment. Continuous peristalsis of the small bowel may
explain the relative lack of peritoneal metastases on intestinal and
mesenteric surfaces. Although not usually classified as a peritoneal recess, the lesser sac may
be a site of internal herniation. There are reports of the small intestine,
caecum, transverse colon or gallbladder migrating through the epiploic
Right infracolic space
foramen into the lesser sac and causing acute abdominal symptoms
(Shrestha et al 2010).
The right infracolic space is a triangular space. It is smaller than its left-
sided counterpart and lies posterior and inferior to the transverse colon
Duodenal recesses
and mesocolon to the right of the small intestinal mesentery. The space
is narrowest inferiorly because the attachment of the root of the mesen-
tery of the small intestine lies well to the right of the midline. Several folds of peritoneum may exist around the fourth part of the
duodenum and the duodenojejunal junction, forming a number of
named recesses (Fig. 63.9). They probably arise during development as
Left infracolic space
a result of minor aberrations of duodenal rotation and fixation. Some
are potential sites of internal herniation (Zonca et al 2008).
The left infracolic space is larger than its right-sided counterpart and is
in free communication with the pelvis. It lies posterior and inferior to Superior duodenal recess
the transverse colon and mesocolon, and to the left of the mesentery The superior duodenal recess is occasionally present, often in associa-
of the small intestine. The sigmoid colon and its mesentery may par- tion with an inferior duodenal recess. It lies directly to the left of the
tially restrict the flow of fluid or blood from this space into the pelvis fourth part of the duodenum, adjacent to the second lumbar vertebra,
to the left of the midline. and behind a crescentic superior duodenal fold. The fold has a semilu-
nar free lower margin, which merges laterally with the peritoneum
Paracolic gutters overlying the left kidney. The inferior mesenteric vein lies under the
parietal peritoneum, directly behind the lateral end of this fold. The
The right and left paracolic gutters are peritoneal depressions on the recess extends superiorly and varies in size, but commonly admits a
posterior abdominal wall alongside the ascending and descending fingertip.
colon, respectively. The principal paracolic gutter lies lateral to the
Inferior duodenal recess
colon on each side. A less obvious medial paracolic gutter may be
present, more often on the right side, if the ascending or descending The inferior duodenal recess is usually present, often in association with
colon possesses a short mesentery for part of its length. The right a superior recess, with which it may share an orifice. It lies to the left
(lateral) paracolic gutter runs from the superolateral aspect of the of the fourth part of the duodenum, adjacent to the third lumbar ver-
hepatic flexure of the colon, down the lateral aspect of the ascending tebra, behind an avascular, triangular inferior duodenal fold, which has
colon and caecum. It is continuous with the peritoneum of the pelvic a sharp upper edge. It usually admits one or two fingertips and extends
cavity below. Superiorly, it is continuous with the peritoneum that lines inferiorly, sometimes behind the fourth part of the duodenum and to
the hepatorenal pouch and with the lesser sac through the epiploic the left, in front of the ascending branch of the left colic artery and the
foramen. Bile, pus, blood or other fluid may run along the gutter and inferior mesenteric vein.
collect in sites distant to the organ of origin. In supine patients, infected
Paraduodenal recess
fluid from the right iliac fossa may ascend in the gutter to the right
subphrenic space. In erect or semi-recumbent positions, fluid from the The paraduodenal recess may occur in conjunction with superior and
stomach, duodenum or gallbladder may run down the gutter to collect inferior duodenal recesses. It lies a little to the left and slightly behind
in the right iliac fossa (mimicking acute appendicitis) or pelvis to form the fourth part of the duodenum, behind a falciform fold of perito-
an abscess. The right paracolic gutter is deeper than the left, which, neum. The free right edge of this fold contains the inferior mesenteric
together with the partial barrier provided by the phrenicocolic ligament, vein and ascending branch of the left colic artery, and is part of the left
may explain why subphrenic collections are more common on the colic mesentery. This recess is the site of a ‘left paraduodenal hernia’
right. (Khan et al 1998).
Retroduodenal recess
RECESSES OF THE PERITONEAL CAVITY The retroduodenal recess is the largest of the duodenal recesses but is
rarely present. It lies behind the third and fourth parts of the duodenum
Peritoneal fossae or recesses within the peritoneal cavity are occasion- in front of the abdominal aorta, is up to 10 cm deep, and has a wide
ally sites of internal herniation. If a loop of intestine becomes stuck in orifice flanked by duodenoparietal peritoneal folds. | 1,533 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Peritoneum and peritoneal cavity
1108.e1
36
RETPAHC
The distribution of peritoneal metastases via the paracolic gutters is
not the same on each side. Peritoneal fluid usually tracks freely along
the right paracolic gutter, whereas the flow of peritoneal fluid running
down the left paracolic gutter from the upper abdomen will be impeded
by any attachments of the sigmoid colon to the left abdominal wall.
Cancer deposits at this site tend to invade the mesentery of the junction
between the sigmoid and descending colon, and therefore necessitate
sigmoid colectomy for tumour clearance.
The superior and inferior recesses of the duodenum may be sites of
occult peritoneal metastases and must be examined in patients having
surgery for peritoneal metastases. | 1,534 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
General arrangement of the peritoneal cavity
1109
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RETPAHC
In addition to these caecal recesses, one or more shallow paracae-
Ascending colon
cal or paracolic recesses may be present. These are simply depres-
Vascular
sions within the right paracolic gutter and are not sites of internal
fold of
caecum herniation.
Superior
Intersigmoid recess
iliocaecal
recess
Ileocaecal The intersigmoid recess is present in fetal life and infancy, but often
fold disappears subsequently. It lies behind and inferior to the apex of the
V-shaped attachment of the sigmoid mesocolon. It opens downwards
Ileum
and varies in shape from a slight depression to a shallow fossa. Its
posterior wall is formed by the parietal peritoneum of the posterior
abdominal wall, where it covers the left ureter as it crosses the bifurca-
tion of the left common iliac artery. It is a rare site for an internal hernia
(Harrison et al 2011).
Internal hernias
Inferior
Caecal fold ileocaecal An internal hernia is a protrusion of a viscus through a normal or
recess abnormal aperture (which includes a surgically created opening) within
Caecum
the confines of the peritoneal cavity (Martin et al 2006). It is possible
Retrocaecal recess Vermiform appendix Mesoappendix
for any of the peritoneal recesses, foramina or cul-de-sacs described in
Fig. 63.10 The peritoneal folds and recesses in the caecal region. this chapter to be associated with the development of an internal
hernia, but with a clinically apparent internal hernia the relevant peri-
toneal recess is usually enlarged and its aperture narrowed compared
to normal. Among the many potential sites for an internal hernia, the
Duodenojejunal recess most common are paraduodenal, followed by pericaecal, and hernias
through the epiploic foramen.
The duodenojejunal or mesocolic recess occurs in a minority of adults.
When present, it is almost never associated with other duodenal
recesses. It is approximately 3 cm deep and lies to the left of the abdom-
ADDITIONAL CLINICAL ASPECTS OF THE
inal aorta, between the duodenojejunal junction and the root of the
PERITONEAL CAVITY
transverse mesocolon. It is bounded above by the pancreas, on the left
by the kidney, and below by the left renal vein. Its circular opening lies
Peritoneal fluid collections
between two peritoneal folds and faces down and to the right.
Mesentericoparietal recess
Fluid collections frequently develop within the peritoneal cavity in
The mesentericoparietal recess or fossa is rarely present. It lies just response to a wide range of pathological processes. In the absence of
below the third part of the duodenum and invaginates the upper part inflammation, peritoneal adhesions or previous surgery, serous fluid
of the mesentery of the small intestine towards the right. Its orifice is tends to be distributed widely between the peritoneal spaces. Simple
large and faces to the left, behind a fold of mesentery raised by the ascites can therefore be drained freely from any convenient dependent
superior mesenteric artery. This recess is the site of the rare ‘right part of the peritoneal cavity; drainage is most commonly performed by
paraduodenal hernia’. blind puncture or ultrasound-guided insertion of a catheter into the
lower left or right paracolic gutters. The mobility of the small bowel
Caecal recesses makes it very unlikely to be injured during this procedure.
Fluid collections caused by inflammatory processes are often much
Peritoneal folds around the caecum may form a variety recesses (Fig. thicker because they contain pus, fibrin or blood. Furthermore, they are
63.10); these have the potential to become sites of internal herniation usually associated with peritoneal adhesions arising from peritoneal
(Rivkind et al 1986). Paracaecal recesses are common sites for abscess inflammation. These factors predispose to the formation of localized
formation after acute appendicitis. fluid collections, which may become walled-off as the inflammatory
process progresses. Any of the peritoneal spaces may develop a localized
Superior ileocaecal recess
collection, but the subphrenic, subhepatic and pelvic spaces are the
The superior ileocaecal recess is usually best developed in children and most common sites since they are well defined by peritoneal folds and
may be absent in the aged or obese. It is a narrow slit bounded in front organs forming their boundaries. These spaces are also the most
by a vascular fold of peritoneum containing the anterior caecal vessels, dependent regions within the peritoneal cavity.
behind by the ileal mesentery, below by the terminal ileum and on the Surgical access to the peritoneal spaces is less often needed today
right by the ileocaecal junction. Its orifice opens to the left. because of advances in radiologically guided percutaneous drainage
using fluoroscopy, ultrasound, computed tomography (CT) or magnetic
Inferior ileocaecal recess
resonance imaging (MRI) guidance. These techniques offer reliable and
The inferior ileocaecal recess is similarly well developed in the young versatile methods of accessing peritoneal spaces, including relatively
but frequently obliterated by fat in adults. It is formed by the ileocaecal inaccessible subhepatic, perihepatic or intermesenteric collections. Pos-
fold, which extends from the anteroinferior aspect of the terminal ileum terolateral translumbar or trans-sciatic approaches can also be used to
to the front of the mesoappendix (or to the appendix or caecum). It is access the retroperitoneum and pelvis, respectively. Occasionally, a sur-
also known as the ‘bloodless fold of Treves’, although it sometimes gical approach is necessary; thus, a subcostal or lateral intercostal inci-
contains blood vessels that bleed if divided during surgery. If inflamed, sion may be required to drain a subphrenic abscess or an inguinal
especially when the appendix and its mesentery are retrocaecal, it may incision to drain a pelvic abscess.
be mistaken for the mesoappendix. The recess is bounded in front by
the ileocaecal fold, above by the terminal ileum and its mesentery, to
Peritoneal dialysis
the right by the caecum, and behind by the upper part of the mesoap-
pendix. Its orifice opens downwards to the left.
The mean surface area of the peritoneum in the adult (female) has been
Retrocaecal recess estimated to be about 1.4 m2 (with the visceral peritoneum accounting
The retrocaecal recess lies behind the caecum. It ascends behind the for about 80% of the total) (Albanese et al 2009). Mesothelium resem-
ascending colon to a variable extent, often being large enough to admit bles vascular endothelium in that it allows the passage of ions and small
an entire finger. It is bounded in front by the caecum (and sometimes molecules. Normally, the volume of fluid transmitted by peritoneal
the proximal ascending colon), behind by the parietal peritoneum, and surfaces is small, but large volumes of fluid can be instilled into the
on each side by caecal folds (parietocolic folds) passing from the peritoneal cavity and then siphoned out, using the peritoneum as a
caecum to the posterior abdominal wall. The vermiform appendix fre- dialysing membrane. This can be used to support individuals with acute
quently occupies this retrocaecal recess (p. 1142). or chronic renal failure. | 1,535 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
PERiTonEum And PERiTonEAl CAviTy
1110
8
noiTCES
Ventriculoperitoneal shunts chemotherapeutic agents (diluted in large volumes of fluid) directly
into the peritoneal cavity. Peritoneal access may be achieved via an
intraperitoneal catheter connected to a subcutaneous port or by repeated
The absorptive capabilities of the peritoneum can be exploited to
paracentesis. The infused chemotherapeutic agents may be retained
absorb excess transitional fluids from several sites in the body. The most
locally for longer than systemically administered agents. Targeting drugs
common of these is the absorption of cerebrospinal fluid diverted into
to the peritoneal space may improve the results of treatment if complete
the peritoneal cavity using a shunt (a fine catheter) from the cerebral
tumour resection is not possible.
ventricles or the intrathecal space. The catheter placed within the peri-
toneal cavity can be equipped with a one-way valve to prevent reflux of
peritoneal fluid into the cerebrospinal fluid. The cerebrospinal fluid is
continuously absorbed by the peritoneum, maintaining a low pressure
within the intraventricular or intrathecal space.
Bonus e-book video
Intraperitoneal cancer chemotherapy
In patients with peritoneal metastases, attempts to optimize the Video 63.1 Surgical exploration of the peritoneal cavity.
benefits of cytoreductive surgery may involve the administration of
KEY REFERENCES
Coakley FV, Hricak H 1999 Imaging of peritoneal and mesenteric disease: Pestieau SR, Wolk R, Sugarbaker PH 2000 Congenital pleuroperitoneal com-
key concepts for the clinical radiologist. Clin Radiol 54:563–74. munication in a patient with pseudomyxoma peritonei. J Surg Oncol
An explanation of the complex anatomy of the upper abdominal peritoneal 73:174–8.
fold suspending the stomach, liver and spleen. Platell C, Cooper D, Papadimitriou JM et al 2000 The omentum. World J
Healy JC, Reznek RH 1999 The anterior abdominal wall and peritoneum. Gastroenterol 6:169–76.
In: Butler P, Mitchell A, Ellis H (eds) Applied Radiological Anatomy. A comprehensive review of the greater omentum.
Cambridge: Cambridge University Press, pp. 189–200. Schnüriger B, Barmparas G, Branco BC et al 2011 Prevention of postoperative
A demonstration of the imaging anatomy of the peritoneal spaces and peritoneal adhesions: a review of the literature. Am J Surg 201:111–21.
reflections using cross-sectional imaging.
Simmons LE, Mir AR 1989 A review of management of pleuroperitoneal
Martin LC, Merkle EM, Thompson WM 2006 Review of internal hernias: communication in five CAPD patients. Adv Perit Dial 5:81–3.
radiographic and clinical findings. AJR 186:703–17. Stringer MD 2009 Eponyms in Surgery and Anatomy of the Liver, Bile Ducts
Meyers M 1994 Dynamic Radiology of the Abdomen: Normal and Patho- and Pancreas. London: Royal Society of Medicine Press.
logic Anatomy. New York: Springer. A short reference book that contains information and illustrations relating to
Meyers MA, Oliphant M, Berne AS et al 1987 The peritoneal ligaments and the original descriptions and the authors of many of the eponyms cited in
mesenteries: pathways of intraabdominal spread of disease. Radiology this chapter (e.g. Cullen, Winslow, Morison).
163:593–604.
A systematic application of anatomic and dynamic principles to the
understanding and diagnosis of intra-abdominal disease. | 1,536 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Peritoneum and peritoneal cavity
1110.e1
36
RETPAHC
REFERENCES
Albanese AM, Albanese EF, Mino JH et al 2009 Peritoneal surface area: Meyers MA, Oliphant M, Berne AS et al 1987 The peritoneal ligaments and
measurements of 40 structures covered by peritoneum: correlation mesenteries: pathways of intraabdominal spread of disease. Radiology
between total peritoneal surface area and the surface calculated by for- 163:593–604.
mulas. Surg Radiol Anat 31:369–77. A systematic application of anatomic and dynamic principles to the
Ashaolu JO, Ukwenya VO, Adenowo TK 2011 Cystoduodenal ligament as an understanding and diagnosis of intra-abdominal disease.
abnormal fold and the accompanying anatomical and clinical implica- Pestieau SR, Wolk R, Sugarbaker PH 2000 Congenital pleuroperitoneal com-
tions. Surg Radiol Anat 33:171–4. munication in a patient with pseudomyxoma peritonei. J Surg Oncol
Autio V 1964 The spread of intraperitoneal infection. Acta Chir Scand Suppl 73:174–8.
36:5–31. Platell C, Cooper D, Papadimitriou JM et al 2000 The omentum. World J
Baessler K, Schuessler B 2000 The depth of the pouch of Douglas in nulli- Gastroenterol 6:169–76.
parous and parous women without genital prolapse and in patients with A comprehensive review of the greater omentum.
genital prolapse. Am J Obstet Gynecol 182:540–4.
Rivkind AI, Shiloni E, Muggia-Sullam M et al 1986 Paracecal hernia: a cause
Boaz NT, Martin AH, Thompson K et al 2011 Structure and functional sig- of intestinal obstruction. Dis Colon Rectum 29:752–4.
nificance of the transverse vesical fold. Clin Anat 24:62–9.
Sanchez NC, Tenofsky PL, Dort JM et al 2001 What is normal intra-
Coakley FV, Hricak H 1999 Imaging of peritoneal and mesenteric disease: abdominal pressure? Am Surg 67:243–8.
key concepts for the clinical radiologist. Clin Radiol 54:563–74.
Schnüriger B, Barmparas G, Branco BC et al 2011 Prevention of postoperative
An explanation of the complex anatomy of the upper abdominal peritoneal
peritoneal adhesions: a review of the literature. Am J Surg 201:111–21.
fold suspending the stomach, liver and spleen.
Shimotsuma M, Shields JW, Simpson-Morgan MW et al 1993 Morpho-
Coulier B 2009 64-row MDCT review of anatomic features and variations physiological function and role of omental milky spots as omentum-
of the normal greater omentum. Surg Radiol Anat 31:489–500. associated lymphoid tissue (OALT) in the peritoneal cavity. Lymphology
Feldberg MA, van Leeuwen MS 1990 The properitoneal fat pad associated 26:90–101.
with the falciform ligament. Imaging of extent and clinical relevance. Shrestha BM, Brown PW, Wilkie ME et al 2010 The anatomy and pathology
Surg Radiol Anat 12:193–202. of the lesser sac: implications for peritoneal dialysis. Perit Dial Int 30:
Hagiwara A, Takahashi T, Sawai T et al 1994 Milky spots as the implantation 496–501.
site for malignant cells in peritoneal dissemination in mice. Cancer Res Simmons LE, Mir AR 1989 A review of management of pleuroperitoneal
54:687–92. communication in five CAPD patients. Adv Perit Dial 5:81–3.
Harrison OJ, Sharma RD, Niayesh MH 2011 Early intervention in intersig- Stringer MD 2009 Eponyms in Surgery and Anatomy of the Liver, Bile Ducts
moid hernia may prevent bowel resection – a case report. Int J Surg Case and Pancreas. London: Royal Society of Medicine Press.
Rep 2:282–4. A short reference book that contains information and illustrations relating to
Healy JC, Reznek RH 1999 The anterior abdominal wall and peritoneum. the original descriptions and the authors of many of the eponyms cited in
In: Butler P, Mitchell A, Ellis H (eds) Applied Radiological Anatomy. this chapter (e.g. Cullen, Winslow, Morison).
Cambridge: Cambridge University Press, pp. 189–200.
Sugarbaker PH 2012 An overview of peritonectomy, visceral resections,
A demonstration of the imaging anatomy of the peritoneal spaces and
and perioperative chemotherapy for peritoneal surface malignancy.
reflections using cross-sectional imaging.
In: Sugarbaker PH (ed) Cytoreductive Surgery and Perioperative Chemo-
Khan MA, Lo AY, Vande Maele DM 1998 Paraduodenal hernia. Am Surg therapy for Peritoneal Surface Malignancy. Textbook and Video Atlas.
64:1218–22. Woodbury, CT: Cine-Med Publishing, pp. 1–30.
Koninckx PR, Renaer M, Brosens IA 1980 Origin of peritoneal fluid in Wassilev W, Wedel T, Michailova K et al 1998 A scanning electron micros-
women: an ovarian exudation product. Br J Obstet Gynaecol 87: copy study of peritoneal stomata in different peritoneal regions. Ann
177–83. Anat 180:137–43.
Martin LC, Merkle EM, Thompson WM 2006 Review of internal hernias: Yoshikawa T, Hayashi N, Maeda E et al 2013 Peritoneal fluid accumulation
radiographic and clinical findings. AJR 186:703–17. in healthy men and postmenopausal women: evaluation on pelvic MRI.
Meyers MA 1973 Distribution of intra-abdominal malignant seeding: AJR 200:1181–5.
dependency on dynamics of flow of ascitic fluid. Am J Roentgenol Zonca P, Maly T, Mole DJ et al 2008 Treitz’s hernia. Hernia 2:531–4.
Radium Ther Nucl Med 119:198–206.
Meyers M 1994 Dynamic Radiology of the Abdomen: Normal and Patho-
logic Anatomy. New York: Springer. | 1,537 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
SUBSECTION: Gastrointestinal tract
CHAPTER
64
Abdominal oesophagus and stomach
ous with the subpleural endothoracic fascia above the diaphragm; it is
ABDOMINAL OESOPHAGUS
thicker, contains more elastin than its inferior counterpart, and runs
cranially and obliquely to fuse firmly with the wall of the oesophagus.
The abdominal oesophagus is 1–2.5 cm in length, and is slightly A variable amount of adipose tissue lies in the triangular interval
broader at the cardiac orifice than at the diaphragmatic aperture. It lies between the two layers of the ligament. The phreno-oesophageal liga-
to the left of the midline and enters the abdomen through the oesopha- ment helps to anchor the oesophagus to the crural muscle fibres of the
geal aperture (formed by the two diaphragmatic crura) at the level of diaphragm and probably acts to limit upward and downward mobility
the eleventh thoracic vertebra (Mirjalili et al 2012). It runs obliquely to of the oesophagus within the hiatus (Kwok et al 1999). In the elderly,
the left and slightly posteriorly, and ends at the gastro-oesophageal the ligament tends to become attenuated and contain more adipose
junction, where it is continuous with the cardiac orifice of the stomach. tissue. The phreno-oesophageal ligament is denser anteriorly where it
The anterior wall of the abdominal oesophagus is effectively longer bridges between the outer layer of the oesophageal wall and the arching
than the posterior wall because of the obliquity of the crura. The fibres of the diaphragmatic crura.
abdominal oesophagus lies posterior to the left lobe of the liver, and The peritoneal reflection posterior to the abdominal oesophagus is
anterior to the left crus, the left inferior phrenic vessels and the left short and continues directly on to the posterior surface of the fundus
greater and lesser splanchnic nerves; its surface is covered by a thin layer of the stomach; it is sometimes referred to as the gastrophrenic liga-
of connective tissue and visceral peritoneum that contain the anterior ment. It encloses the oesophageal branches of the left gastric vessels
and posterior vagus nerves, as well as the oesophageal branches of the and the coeliac branches of the posterior vagus and can thus be con-
left gastric vessels. The anterior and posterior vagi may be single or sidered to form an extremely short, wide mesentery to the abdominal
composed of multiple trunks (Jackson 1949); the anterior is closely oesophagus. In adults, a fat pad may be visible beneath the peritoneum
applied to the anterior outer surface of the longitudinal muscle coat of over the anterior surface of the gastro-oesophageal junction and can be
the oesophagus while the posterior usually lies within loose connective a useful surgical marker of the gastro-oesophageal junction.
tissue immediately posterior and to the right of the oesophagus, making
its identification during surgery somewhat easier. Unlike the more Hiatus hernia
proximal parts of the oesophagus, the muscular wall of the abdominal
oesophagus is composed entirely of smooth muscle. Available with the Gray’s Anatomy e-book
The abdominal oesophagus is effectively tethered to the margins of
the muscular oesophageal hiatus in the diaphragm by the phreno-
oesophageal ligament (Fig. 64.1) (Kwok et al 1999). This is formed by VASCULAR SUPPLY AND LYMPHATIC DRAINAGE
two circumferential layers of elastin-rich connective tissue containing
some smooth muscle fibres. The inferior layer is an extension of the Arteries
subperitoneal transversalis fascia below the diaphragm; it is thin and
only loosely attached to the oesophagus. The superior layer is continu-
The abdominal oesophagus is supplied by numerous oesophageal
branches of the left gastric artery. These ascend beneath the visceral
Longitudinal oesophageal muscle peritoneum to supply perforating branches to the intramural and sub-
Circular oesophageal muscle mucosal plexuses. The posterior surface usually receives an additional
supply via branches of the upper short gastric arteries, reinforced by
Gradual slight muscular thickening
Oesophageal terminal arteries from the oesophageal branches of the thoracic aorta
mucosa Phreno-oesophageal ligament and occasionally an ascending branch of the posterior gastric artery
(ascending or upper limb) (Liebermann-Meffert et al 1987).
Submucosa Supradiaphragmatic
(endothoracic) fascia Veins
Diaphragm Diaphragm
Infradiaphragmatic Mucosal and submucosal veins drain via plexuses to the left gastric and
(transversalis) fascia
upper short gastric veins in the abdomen and to the azygos/hemiazygos
Phreno-oesophageal system of veins in the thorax. The distal oesophagus is an important
ligament site of portosystemic anastomosis where oesophageal varices develop
(descending limb)
in portal hypertension (see below).
Phreno-oesophageal Lymphatic drainage
ligament
(descending limb)
The oesophagus has a freely anastomosing plexus of lymphatics in the
lamina propria, submucosa and muscularis propria. The lower third
Subhiatal fat ring
primarily drains caudally to left gastric and left and right paracardial
Zigzag (Z) line: nodes, and from there to coeliac nodes. In lower oesophageal cancer,
juncture of lymph also drains cranially to mediastinal lymph nodes (Aikou et al
oesophageal and Peritoneum 1987).
gastric mucosa
Cardiac notch
Cardiac region of INNERVATION
stomach (cardia)
Gastric folds (rugae)
The oesophagus has a well-developed intrinsic nervous system consist-
Fig. 64.1 The anatomical structures around the abdominal oesophagus. ing of a ganglionated myenteric plexus and a sparsely ganglionated
(Reprinted from Netter Anatomy Illustration Collection, © Elsevier Inc. All submucosal plexus, modulated by extrinsic autonomic nerves. Parasym-
Rights Reserved.) pathetic innervation of the abdominal oesophagus is derived directly 1111 | 1,538 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Abdominal oesophagus and stomach
1111.e1
46
RetpAhc
Hiatus hernia is a relatively common condition involving expansion of
the oesophageal hiatus and herniation of the stomach through the
diaphragm into the mediastinum. It is more common in the elderly
and the obese. There are two types of hiatus hernia: the sliding type,
which accounts for at least 90%, and the para-oesophageal or mixed
type, which makes up the remainder (Roman and Kahrilas 2014). A
hiatus hernia may not cause any symptoms or it may be associated with
symptoms of gastro-oesophageal reflux. Para-oesophageal hernias can
cause obstruction and/or ischaemia of the herniated stomach. Treat-
ment of a symptomatic sliding hiatal hernia is directed at managing
associated gastro-oesophageal reflux, which may require anti-reflux
surgery. | 1,539 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
AbdominAl oesophAgus And stomAch
1112
8
noitces
from the thoracic peri-oesophageal plexus and, to a lesser extent, from drawn from the angular incisure to an inconstant indentation on the
the anterior and posterior vagi. These nerves are motor to the distal greater curvature defines the lower boundary of the body. The pyloric
oesophagus and both stimulatory and inhibitory to the lower oesopha- antrum extends from this line to where the stomach narrows to become
geal sphincter, maintaining basal tone and coordinating distal oesopha- the pyloric canal (1–2 cm long), which terminates at the pyloric orifice
geal peristalsis with relaxation of the sphincter during swallowing (the (Didio and Anderson 1968).
latter being mediated by intrinsic nitrergic inhibitory neurones under
vagal control). Sympathetic supply of the distal oesophagus originates
from the fifth to twelfth thoracic spinal segments mainly via the greater GASTRIC RELATIONS
and lesser splanchnic nerves and the coeliac plexus. Nociceptive signals
are conveyed by afferent nerves accompanying sympathetic nerves and Gastric curvatures
by vagal afferents, which are also involved in mechanosensory signal-
ling (Neuhuber et al 2006). Lesser curvature
The lesser curvature extends between the cardiac and pyloric orifices
STOMACH and forms the medial border of the stomach. It descends from the
medial side of the oesophagus in front of the decussating fibres of the
right crus of the diaphragm, curves downwards and to the right, and
The stomach is the widest part of the alimentary tract and lies between
lies anterior to the superior border of the pancreas (Fig. 64.3). It ends
the oesophagus and the duodenum. It performs numerous functions,
at the pylorus, just to the right of the midline. In the most dependent
including the temporary storage of ingested nutrients; mechanical
breakdown of solid food; chemical digestion of proteins; regulation of
the passage of chyme into the duodenum; secretion of intrinsic factor
for vitamin B absorption; secretion of gut hormones; and secretion of Cardiac notch
12
acid to aid digestion (including the absorption of iron). It is also impor-
tant in microbial defence.
The stomach is situated in the upper abdomen, extending from the
left upper quadrant downwards, forwards and to the right, lying in the Abdominal part Fundus
left hypochondrium, epigastrium and umbilical regions. It occupies a of oesophagus
recess beneath the diaphragm and anterior abdominal wall bounded
by the upper abdominal viscera on either side. The mean capacity of Cardiac region
the stomach increases from approximately 20–30 ml at birth to approx-
imately 1000–1500 ml in adults. The peritoneal surface of the stomach Lesser curvature Body
is interrupted by the attachments of the greater and lesser omenta,
which define the greater and lesser curvatures and separate the anterior Angular incisure
and posterior surfaces.
Greater
PARTS OF THE STOMACH curvature
For descriptive purposes, the stomach can be divided into a fundus,
body, pyloric antrum and pylorus by artificial lines drawn on its external
surface (Fig. 64.2). The internal appearance and microstructure of these
regions vary. The fundus is dome-shaped and projects above and to the
left of the oesophageal opening (cardiac (cardial) orifice) to lie in Duodenum Pyloric antrum
contact with the left dome of the diaphragm; it lies above a horizontal
line from the cardiac notch to the greater curvature. The body extends Pylorus Intermediate sulcus
from the fundus to the angular incisure (incisura angularis), a constant
external notch at the lower end of the lesser curvature. The cardia is the Pyloric canal
region of the stomach adjacent to the oesophageal opening. A line Fig. 64.2 The parts of the stomach.
Fig. 64.3 The posterior relations
of the stomach.
Left hemidiaphragm
Left inferior phrenic artery
Decussating fibres
of the right crus
Left suprarenal gland
Spleen
Splenic artery
Origin of mesentery of
transverse colon
Body of pancreas
Left kidney
Duodenojejunal flexure | 1,540 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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part, there is typically a notch, the angular incisure, whose position and crus and sometimes the left suprarenal gland. The left gastric vessels
appearance vary with gastric distension. The lesser omentum is attached reach the lesser curvature at the right extremity of this bare area. The
to the lesser curvature and contains the right and left gastric vessels. gastrophrenic ligament passes from the lateral aspect of this bare area
to the inferior surface of the diaphragm. The posterior surface of the
Greater curvature
stomach lies anterior to the left crus and lower fibres of the diaphragm,
The greater curvature is two to three times longer than the lesser the left inferior phrenic vessels, the left suprarenal gland, the superior
(Csendes and Burgos 2005). It starts from the cardiac notch, formed pole of the left kidney, the splenic artery, the anterior surface of the
between the lateral border of the abdominal oesophagus and the pancreas, and the upper layer of the transverse mesocolon (see Fig.
fundus of the stomach, and arches upwards, posterolaterally and to the 64.3). Together, these form the shallow stomach bed, which is separated
left. Its highest convexity, the apex of the fundus, is approximately level from the stomach by the lesser sac (over which the stomach slides as it
with the left sixth rib anteriorly but varies between individuals and with distends). The upper left part of the posterior surface curves anterolater-
respiration (Mirjalili et al 2012). From this point, it sweeps inferiorly ally and lies in contact with the visceral surface of the spleen. The
and anteriorly, slightly convex to the left, almost as far as the tenth transverse mesocolon separates the stomach from the duodenojejunal
costal cartilage in the supine position, where it turns medially to end flexure and proximal jejunum.
at the pylorus in the transpyloric plane at the lower border of the first
lumbar vertebra. There is frequently a groove, the intermediate sulcus,
in the curvature close to the pyloric canal. The start of the greater cur- GASTRIC ORIFICES
vature is covered by peritoneum, which continues over the anterior
surface of the stomach. Laterally, the greater curvature gives attachment
Cardiac orifice and gastro-
to the gastrosplenic ligament and, below this, to the greater omentum,
oesophageal junction
which contains the gastroepiploic vessels. The gastrosplenic ligament
and the greater omentum, together with the gastrophrenic and spleno-
renal ligaments, are continuous derivatives of the original dorsal meso- The oesophagus opens into the stomach at the cardiac orifice (see Fig.
gastrium; their names merely indicate regions of the same continuous 64.1). It is usually situated to the left of the midline behind the seventh
sheet of peritoneum and its associated connective tissue. costal cartilage at the level of the eleventh thoracic vertebra (Mirjalili
et al 2012). It is, on average, about 40 cm from the incisor teeth in the
Gastric volvulus
adult. The right side of the abdominal oesophagus is continuous with
the lesser curvature and the left side with the greater curvature.
Available with the Gray’s Anatomy e-book Internally, the transition between the oesophagus and stomach is
difficult to define because gastric fundal mucosal folds extend a variable
Gastric surfaces distance up the abdominal oesophagus. For practical purposes, the
gastro-oesophageal junction is usually identified by a circumferential
‘zigzag’ line (‘Z line’) between the pale pink oesophageal squamous
When the stomach is empty and contracted, the anterior and posterior
epithelium above and the red columnar epithelium below. In the
surfaces tend to face superiorly and inferiorly, but as the stomach
healthy oesophagus, the Z line is located at the proximal extent of the
distends, they face progressively more anteriorly and posteriorly
gastric mucosal folds. When metaplastic columnar epithelium extends
(Fig. 64.4).
above the gastric folds into the lower oesophagus, it is regarded
Anterior (superior) surface as pathological and termed Barrett’s oesophagus. The presence of a
The entire anterior (superior) surface of the stomach is covered by peri- sliding hiatus hernia with or without Barrett’s oesophagus can make
toneum. The lateral part of the anterior surface lies posterior to the left
costal margin in contact with the diaphragm, which separates it from
the left pleura, the base of the left lung, the pericardium and the left
seventh to ninth ribs and costal cartilages (Fig. 64.5). It also lies pos-
terior to the costal attachments of the upper fibres of transversus Spleen Transversus abdominis Left lobe of liver
abdominis. The upper left part of this surface curves posteriorly and lies
in contact with the visceral surface of the spleen. The right half of the
anterior surface is related superiorly to the left lobe of the liver and
inferiorly to the anterior abdominal wall, through which it can be
accessed by a needle for placement of a gastrostomy tube (see below).
When the stomach is empty, the transverse colon may lie adjacent to
the anterior surface.
Posterior (inferior) surface
The posterior surface is covered by peritoneum, except near the cardiac
orifice, where a small, triangular area contacts the left diaphragmatic
Axis
Posterior rectus sheath
Axis
Anterior/ Anterior
superior surface
surface
Posterior/
inferior
surface
Greater curvature/
line of attachment of Diaphragm Stomach Transverse colon
Empty Full gastrocolic omentum
Fig. 64.5 Anterior relations of the stomach, viewed from behind. The
Fig. 64.4 Axes of the empty and full stomach. As the stomach distends, fibres of the diaphragm (oblique), transversus abdominis (transverse) and
the greater curvature ‘rolls’ downwards and the anterosuperior surface rectus abdominis (vertical) can be seen through the outlines of the
comes to lie almost completely vertical as the anterior surface. stomach and its visceral relations. | 1,541 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Volvulus of the stomach is much less common than volvulus of either
the sigmoid colon or the caecum. Two types of gastric volvulus may
occur. The first, organoaxial volvulus, occurs about an axis of rotation
running from below the cardiac orifice to the pylorus. The antrum, body
and fundus rotate upwards, such that the greater curvature comes to lie
above the lesser curvature. The second type, mesenteroaxial volvulus,
occurs about an axis drawn ‘across’ the body of the stomach, usually
just above the angular incisure. This type of volvulus is perpendicular
to the axis of organoaxial volvulus. The distal body and antrum rotate
anteriorly, superiorly and laterally while the upper body and fundus
rotate posteriorly, medially and inferiorly. Although it is relatively
mobile within the upper abdomen, the stomach is normally tethered
at the gastro-oesophageal junction and the pylorus, to the spleen by the
gastrosplenic ligament, and to the liver by the lesser omentum. The
attachment to the transverse colon via the gastrocolic omentum also
restrains the stomach but it is the most mobile attachment. For either
type of gastric volvulus to occur, some or all of these points of tethering
must be loosened either by previous surgical division or by chronic
lengthening and laxity of their connective tissue. Organoaxial volvulus
is most common because the lesser omentum, gastrosplenic ligament
and gastrocolic omentum are more likely to undergo chronic lengthen-
ing by traction than the other attachments of the stomach. Mesentero-
axial volvulus requires the gastro-oesophageal junction and pylorus to
be sufficiently mobile as to come into close approximation, which is
much less common. Despite the rich arterial supply of the stomach,
either type of volvulus may cause a strangulating obstruction.
Provided the detorted stomach is viable, gastric volvulus is typically
managed by fixation of the anterior surface of the stomach to the ante-
rior abdominal wall (‘gastropexy’) (García et al 2013). Gastric volvulus
of the organoaxial type is frequently associated with a para-oesophageal
hiatus hernia, which must also be repaired. This surgery can usually be
carried out laparoscopically. | 1,542 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
AbdominAl oesophAgus And stomAch
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endoscopic identification of the gastro-oesophageal junction particu- releasing nitric oxide leads to relaxation of the sphincter. Muscle tone
larly difficult. is reduced in advance of the oesophageal peristaltic wave during swal-
Externally, a fat pad is often present in adults beneath the perito- lowing and raised again after the food bolus has passed. During inspira-
neum over the anterior surface of the gastro-oesophageal junction. The tion, the greater negative intrathoracic pressure increases the
junction is also demarcated by a sling of longitudinal and oblique gastro-oesophageal pressure gradient, but this is offset by increased
gastric muscle fibres that forms a loop on the superior, left, side of the pressure in the HPZ from contraction of the peri-oesophageal fibres of
gastro-oesophageal junction between the oesophagus and the stomach. the right diaphragmatic crus. Activation of the crural muscle slightly
before the rest of the diaphragmatic muscle facilitates this anti-reflux
Lower oesophageal sphincter and gastro-
mechanism.
oesophageal reflux Reflux of gastric contents into the lower oesophagus as a result of
At rest, there is a pressure gradient across the gastro-oesophageal junc- transient relaxation of the lower oesophageal sphincter occurs as a
tion, reflecting the negative intrathoracic pressure transmitted to the normal event in most individuals on a daily basis. Prolonged episodes
thoracic oesophagus and the positive intra-abdominal pressure trans- of acid reflux as a result of a weak lower oesophageal sphincter or
mitted to the stomach (augmented by any contraction of the stomach). sliding hiatus hernia may cause oesophagitis and its associated compli-
Several anatomical and physiological factors normally prevent gastro- cations. Surgical procedures to prevent abnormal reflux aim to restore
oesophageal reflux. The two major anti-reflux mechanisms are the toni- a normal length of intra-abdominal oesophagus, repair any hiatus
cally contracted, specialized, thickened intrinsic circular smooth muscle hernia and increase the pressure surrounding the intra-abdominal
of the lower oesophagus, which is reinforced by the extrinsic encircling oesophagus; this is usually achieved by wrapping the fundus of the
fibres of the right diaphragmatic crus. Together, they exert a radial pres- stomach around the intra-abdominal oesophagus (fundoplication).
sure on the lower 2–4 cm of oesophagus, creating an effective high- The converse type of lower oesophageal sphincter dysfunction occurs
pressure zone (HPZ) that can be measured by electromyography or in achalasia, which is characterized by reduced or absent ganglion cells
manometry (Paterson 2001, Mittal and Goyal 2006, Hershcovici et al in the myenteric plexus of the distal oesophagus and gastro-oesophageal
2011). The description of the intrinsic muscles of the lower oesophageal junction. Loss of inhibitory innervation of the sphincter leads to
sphincter can be refined further to include clasp-like semicircular impaired relaxation, causing dysphagia and proximal oesophageal dila-
smooth muscle fibres on the right side of the oesophagus and sling-like tion. Management of this condition involves disruption of the hyper-
oblique gastric muscle fibres on the left side (Preiksaitis and Diamant tonic muscle fibres by balloon dilation or surgical myotomy (‘Heller’s
1997, Stein et al 1995). The distribution of these muscle fibres corre- cardiomyotomy’).
sponds to the anatomical and functional asymmetry of the HPZ.
At and just below the level of entry of the abdominal oesophagus Barrett’s oesophagus
into the stomach, the circular fibres of the intermediate layer of the The squamous epithelium lining the lower oesophagus may be patho-
muscularis externa lying over the upper lesser curvature are particularly logically replaced by a metaplastic ‘intestinalized’ columnar epithelium
pronounced; they are sometimes referred to as ‘clasp’ fibres and exert known as ‘Barrett’s oesophagus’ (see Commentary 1.4). This process
fairly constant myogenic tone (Fig. 64.6). Since the oesophagus passes results from chronic episodic reflux of gastric acid and bile into the
obliquely into the stomach, the tone in the clasp fibres rises with lower oesophagus (Dvorak et al 2007). The abnormal intestinal meta-
increasing gastric distension and they may act to draw the anterior and plasia may extend proximally for a variable length from the gastro-
posterior surfaces together, increasing the tone at the gastro-oesophageal oesophageal junction and associated macroscopic mucosal changes can
junction and contributing to the HPZ. Several minor anti-reflux factors be seen on endoscopy. The presence of Barrett’s oesophagus confers a
also exist: the folds of gastric mucosa present at the gastro-oesophageal significantly increased risk of oesophageal adenocarcinoma, although
junction form a mucosal rosette that helps to create a fluid- and gas- the condition can remain stable or even regress with appropriate
tight seal from the basal tonic contraction of the muscular wall of the medical therapy (Yousef et al 2008).
lower oesophagus; the angle of the cardiac orifice (angle of His),
formed, in part, by the pull of the oblique fibres of the innermost layer
Pyloric orifice
of gastric smooth muscle, thereby constituting a type of ‘flap valve’; and
the length of the abdominal oesophagus, which is buttressed externally
by pads of adipose tissue at and below the level of the oesophageal The pyloric orifice is the opening from the stomach into the duodenum.
hiatus. These anatomical and physiological features are collectively When the body is supine and the stomach empty, it typically lies
referred to as the lower oesophageal sphincter. The oesophageal part of 1–2 cm to the right of the midline in the transpyloric plane (the lower
the lower oesophageal sphincter is controlled by the intramural plex- border of the body of the first lumbar vertebra). The pyloric sphincter
uses of the enteric nervous system; activation of inhibitory neurones is formed by a circumferential thickening of circular muscle interlaced
with connective tissue septa and some longitudinal muscle fibres, and
is palpably thicker than the adjacent stomach and duodenum. The
circular pyloric constriction on the surface of the stomach usually indi-
cates the location of the pyloric sphincter, and may be marked by a
prepyloric vein that crosses the anterior surface in a caudal direction.
Infantile hypertrophic pyloric stenosis is due to idiopathic hypertro-
Longitudinal oesophageal muscle (cut)
phy of the circular muscle of the pylorus and causes gastric outlet
Cardiac notch obstruction in early infancy. It is readily treated by dividing the thick-
Circular oesophageal muscle ened pyloric muscle (pyloromyotomy).
Fundus of
(shown here as spiral)
stomach
GASTRIC FORM AND INTERNAL APPEARANCES
Numerous factors influence both the form and the position of the
Circular ‘clasp’ fibres below the stomach, including the posture and build of the individual, the extent
gastro-oesophageal junction to which the stomach is filled, the position of the surrounding viscera,
and the tone of the abdominal wall and gastric musculature. The empty
Window cut in middle circular
muscle layer of stomach stomach is most commonly J-shaped, the fundus usually contains gas,
and, in the erect posture, the pylorus descends to the level of the second
Innermost oblique muscle or third lumbar vertebra. The lowest part of the antrum may lie below
layer of stomach (forms sling)
the level of the umbilicus, and the overall axis of the organ is slightly
Outer longitudinal muscle inclined from the vertical (Fig. 64.7). In short, obese individuals, the
layer of stomach (cut) axis of the stomach lies more towards the horizontal as a ‘steer-horn’
shape.
The extent of filling mainly affects the shape and position of the
body of the stomach. As the stomach fills, it expands forwards and
downwards but, when the colon or small bowel is distended, the fundus
Fig. 64.6 Detail of the arrangements of the muscle layers of the enlarges towards the liver and diaphragm. As stomach capacity increases,
oesophageal and gastric walls. (Reproduced and modified from Netter the pylorus is displaced to the right and the axis of the whole organ lies
Anatomy Illustration Collection, © Elsevier Inc. All Rights Reserved.) in a more oblique direction (see Fig. 64.4). | 1,543 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
stomach
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B C
Areae gastricae
Fig. 64.7 Double contrast barium meal films. A, In the erect position, the stomach has a more
‘J’-shaped configuration. B, Initial stomach filling demonstrates a horizontally lying stomach with
A prominent gastric rugal folds. C, The areae gastricae within the antrum are clearly identified on
distension of the stomach.
Fig. 64.8 Endoscopic appearances of the
stomach. A, The cardiac orifice and fundus from
below, showing the pronounced lateral mucosal
fold at the cardiac orifice. B, The body and greater
curvature, showing mucosal folds (‘magenstrasse’).
C, The antrum, showing the internal appearance
of the incisura angularis. D, The prepyloric antrum
and opening of the pyloric canal.
A B
C D
Internal appearances
In the partially distended stomach, the mucosa of the body and, to
a lesser extent, the fundus is thrown into longitudinal folds (rugae) (see
During endoscopic examination (Fig. 64.8), the stomach is typically at Fig. 64.7). These are most obvious on the anterolateral, lateral and
least partially distended by air. The cardiac orifice and the lowest portion posterolateral parts of the stomach, towards the greater curvature. The
of the abdominal oesophagus viewed from above are typically closed smoother mucosa along the lesser curvature forms a ‘gastric canal’ or
at rest by tonic contraction of the lower oesophageal sphincter. The ‘magenstrasse’ that enables liquids entering the stomach to be fast-
transition between the pale pink squamous epithelium of the oesopha- tracked to the pylorus (see Fig. 64.8).
gus and the red columnar epithelium of the stomach, the ‘Z line’, is The areae gastricae within the antrum are small undulations of the
usually clearly visible at the proximal extent of the gastric mucosal folds mucosal surface that give a subtle cobblestone-type appearance on
(Silverstein and Tytgat 1991). Viewed retrogradely from within the dis- double contrast barium meal examination (see Fig. 64.7) (Mackintosh
tended stomach, the cardiac orifice lies medial to the fundus, with a and Kreel 1977). The few folds present in the antrum when the stomach
mucosal fold between the two corresponding to the acute angle at this is relaxed disappear with distension. The antrum adjacent to the pyloric
orifice. The mucosa also appears slightly thickened, forming part of the canal, the prepyloric antrum, has a smooth mucosal surface that culmi-
‘mucosal rosette’ that lines the orifice and contributes to its closure (see nates in a slight puckering of the mucosa at the pyloric orifice, caused
above). by contraction of the pyloric sphincter. | 1,544 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
AbdominAl oesophAgus And stomAch
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Short gastric arteries Right hepatic Right medial sectoral Left hepatic Right gastric Left gastric Splenic
Oesophageal branch artery artery artery artery artery artery
Left gastric artery
Common hepatic artery
Gastroduodenal artery
Hepatic artery
Right gastric artery Epiploic branch
Gastric branch A
Right gastroepiploic artery
Left gastroepiploic artery
Cystic artery Gastroduodenal Common hepatic Right gastroepiploic
Fig. 64.9 The arterial supply of the stomach. A posterior gastric artery is
artery artery artery
not shown in this illustration.
Gastrostomy Left gastric
artery
Available with the Gray’s Anatomy e-book
Splenic artery
VASCULAR SUPPLY AND LYMPHATIC DRAINAGE
Common hepatic
Arteries
artery
The arterial supply to the stomach comes predominantly from the
coeliac trunk, although intramural anastomoses exist with arteries of Coeliac trunk
other origins at the two ends of the stomach (Figs 64.9–64.11). The left B
gastric artery usually arises directly from the coeliac trunk. The short
gastric arteries, left gastroepiploic artery and, when present, the poste-
rior gastric artery are branches of the splenic artery. The right gastric
artery and right gastroepiploic artery arise from the hepatic artery and Coeliac trunk
its gastroduodenal branch, respectively.
left gastric artery
The left gastric artery is the smallest branch of the coeliac trunk. It Common hepatic
ascends to the left of the midline and crosses over the lower end of the artery
left crus of the diaphragm beneath a fold of peritoneum in the upper
posterior wall of the lesser sac (the gastropancreatic fold). Here, it lies
Splenic artery
adjacent to the left inferior phrenic artery and medial or anterior to the
left suprarenal gland. It runs forwards into the superior portion of the
lesser omentum adjacent to the upper end of the lesser curvature, and
then turns anteroinferiorly to run along the lesser curvature between
C
the two peritoneal leaves of the lesser omentum. At the highest point
of its course, it gives off one or more oesophageal branches. In its course
along the lesser curvature, it gives off multiple branches that run on to Fig. 64.10 The coeliac trunk and its branches. A, Digital subtraction
the anterior and posterior surfaces of the stomach, after which it anas- angiogram. B–C, Digital reformatted multislice CT angiograms. (A,
tomoses with the right gastric artery in the region of the angular incisure. Courtesy of Dr James McCall, Chelsea & Westminster Hospital, London.
The left gastric artery (replaced or accessory) may rarely arise from B and C, Courtesy of GE Worldwide Medical Systems.)
the common hepatic artery or its left branch, or directly from the
abdominal aorta (Panagouli et al 2013). The most common of these
variations is an origin from the left branch of the hepatic artery, when anastomose with branches of the left gastric and left gastroepiploic
the left gastric artery passes between the peritoneal layers of the upper arteries. Rarely, an accessory left gastric artery may arise with these
lesser omentum to reach the lesser curvature of the stomach. However, vessels from the distal splenic artery.
a replaced/accessory left hepatic artery arising from the left gastric artery
is more common than a replaced/accessory left gastric artery origin. left gastroepiploic artery
The left gastroepiploic artery is the largest branch of the splenic artery.
short gastric arteries It arises near the splenic hilum and runs anteroinferiorly between the
For practical purposes, the short gastric arteries may be defined as those layers of the gastrosplenic ligament into the upper gastrocolic omentum.
arteries arising above the level of the splenic artery and supplying the Here, it descends between the layers of peritoneum close to the greater
fundus of the stomach on its greater curvature. The short gastric arteries curvature and often anastomoses with the right gastroepiploic artery. It
are variable in number: commonly, between five and seven. They arise gives off gastric branches to the fundus of the stomach through the
from the splenic artery or its terminal divisions, or from the proximal gastrosplenic ligament, and to the body of the stomach through the
left gastroepiploic artery, and pass between the layers of the gastro- gastrocolic omentum. These are necessarily longer than the gastric
splenic ligament to supply the gastric fundus and cardiac orifice. They branches of the right gastroepiploic artery and may be up to 8 cm long. | 1,545 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Since the lower half of the anterior surface of the stomach lies adjacent
to the anterior abdominal wall in the left upper quadrant, it may be
readily accessed to form a gastrostomy. The mobility of the stomach
allows it to be approximated to the parietal peritoneum on the upper
anterior abdominal wall, and a communication can then be established
between the lumen of the stomach and the skin surface. This may be
performed as an open surgical procedure but is much more commonly
undertaken by percutaneous puncture of the stomach, guided by an
endoscope within the gastric lumen or by radiological or laparoscopic
visualization of the stomach. Caution is needed to avoid inadvertent
transfixion of the transverse colon, which may be interposed between
the stomach and anterior abdominal wall. | 1,546 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Posterior gastric Extramural arteries Pyloric artery Submucous plexus
artery
Left gastric artery origin:
Left hepatic artery
Abdominal aorta
(not shown)
Mucosal arteries Duodenum Pyloric sphincter Pyloric antrum
Fig. 64.12 The blood supply of the stomach and the proximal duodenum:
Right gastric artery origin: Incomplete gastroepiploic a scheme of arterial arrangements at the gastroduodenal junction. Dotted
Common hepatic artery arcade lines indicate sites where the submucous plexus may be non-continuous.
Fig. 64.11 Principal variations in the gastric arterial supply. Accessory Shaded areas represent the muscular layer of the visceral wall. (Redrawn
vessels or possible replaced origins of vessels are shown by pale pink courtesy of C Piasecki, Department of Anatomy, Royal Free Hospital
lines. School of Medicine, London, and the Journal of Anatomy.)
Epiploic (omental) branches arise along the course of the vessel and supplying the stomach form extensive arterial anastomoses throughout
descend between the layers of the gastrocolic omentum into the greater the wall of the stomach but particularly in the submucosa. The right
omentum. A particularly large epiploic branch commonly originates and left gastroepiploic arteries and left and right gastric arteries anasto-
close to the origin of the left gastroepiploic artery, descends in the mose along the greater and lesser curvatures, respectively. Anastomoses
lateral portion of the greater omentum and provides a large arterial also exist in the fundus between the short gastric and left gastric arteries,
supply to the lateral half of the omentum. and in the antrum between the right gastric and right gastroepiploic
arteries. The rich arterial supply to the stomach ensures that the high
posterior gastric artery mucosal blood flow required for physiological functioning is main-
A posterior gastric artery supplying the posterior wall of the upper part tained even if one or more vessels become occluded; the stomach shows
of the gastric body is commonly present but there has been a lack of considerable resistance to ischaemia, even when multiple arterial sup-
consensus regarding its origin, course and distribution. It usually arises plies are lost.
from the splenic artery (usually from its mid section), posterior to the The pyloric arteries are branches of the right gastric and right gastro-
body of the stomach (see Fig. 64.11), and ascends behind the perito- epiploic arteries. They pierce the duodenal wall around its entire cir-
neum of the lesser sac towards the fundus to reach the posterior surface cumference just distal to the sphincter and reach the submucosa. Here,
of the stomach. It may also arise from the left gastric artery or coeliac they divide into two or three rami that run towards the stomach in the
trunk (Loukas et al 2007). submucosa of the pyloric canal and terminate in the mucosa of the
pyloric antrum (Fig. 64.12) (Piasecki 1974). The pyloric arteries anas-
Right gastric artery
tomose with submucosal arteries in the duodenum and gastric antrum
The right gastric artery is a relatively small artery that usually arises from close to their origin and termination, respectively. The pyloric sphincter
the hepatic artery proper and runs forwards into the lesser omentum muscle is supplied by gastric and pyloric arteries via branches that leave
just above the first part of the duodenum. It then travels within the their parent vessels in the subserosal and submucosal levels to penetrate
lesser omentum along the lesser curvature of the stomach, giving off the sphincter.
multiple branches to the anterior and posterior surfaces of the stomach,
before anastomosing with the left gastric artery. In a significant minority dieulafoy lesions
of individuals, it may originate from the common hepatic artery, left
hepatic artery or gastroduodenal artery (Yamagami et al 2010).
Available with the Gray’s Anatomy e-book
Right gastroepiploic artery
The right gastroepiploic artery usually originates from the gastroduode- Veins
nal artery behind the first part of the duodenum, anterior to the head
of the pancreas. It passes inferiorly towards the midline just below the The veins draining the stomach ultimately empty into the portal vein.
pylorus and then runs laterally along the greater curvature between the A rich submucosal and intramural venous network gives rise to veins
layers of the gastrocolic omentum about 1–2 cm from the greater cur- that usually accompany the corresponding named arteries and drain
vature of the stomach. It ends by anastomosing with the left gastroepi- into either the splenic or superior mesenteric veins, although some pass
ploic artery (although this anastomosis is variably developed (Ndoye directly into the portal vein. The course and distribution of the veins is
et al 2006) and may be absent). The right gastroepiploic artery gives off highly variable even up to the level of the major named vessels.
gastric branches that ascend on to the anterior and posterior surfaces
of the antrum and lower body of the stomach; epiploic branches that short gastric veins
descend into the greater omentum; and branches that contribute to the Three to five short gastric veins drain the gastric fundus and the upper
supply of the inferior aspect of the first part of the duodenum. part of the greater curvature into the splenic vein or one of its large
tributaries.
Arterial anastomoses of the stomach
Oesophageal arteries originating from the thoracic aorta anastomose left gastroepiploic vein
with vessels supplying the fundus of the stomach in the region of the The left gastroepiploic vein drains both anterior and posterior surfaces
cardiac orifice. At the pyloric orifice, the extensive network of vessels of the body of the stomach and the adjacent greater omentum via
supplying the duodenum allows for some anastomosis between multiple tributaries. It runs superolaterally along the greater curvature,
branches of the superior mesenteric artery and pyloric vessels derived between the layers of the gastrocolic omentum, and drains into the
from arteries arising from the coeliac trunk. The major named vessels splenic vein within the gastrosplenic ligament. | 1,547 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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In patients requiring replacement of the oesophagus for severe con-
genital anomalies or after resection for cancer, a gastric tube supplied
by the left gastroepiploic artery can be fashioned from the greater cur-
vature of the stomach and anastomosed to the cervical oesophagus
(Arul and Parikh 2008).
The right gastroepiploic artery has been used for coronary artery
revascularization in some centres and this may pose a particular hazard
if the patient subsequently requires surgery for gastric cancer.
Abnormalities of the intramural vascularity of the stomach are a rare
cause of acute upper gastrointestinal haemorrhage. The so-called ‘Dieu-
lafoy’ lesion occurs most often near the lesser curvature within a few
centimetres of the gastro-oesophageal junction and consists of an
abnormally large artery that penetrates the muscular coat of the
stomach, runs a tortuous course in the submucosa, and protrudes
through a small mucosal defect, where it is vulnerable to rupture (Baxter
and Aly 2010). | 1,548 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
AbdominAl oesophAgus And stomAch
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Right gastroepiploic vein gastrectomy and gastric lymphadenectomy
The right gastroepiploic vein drains the greater omentum, distal body
and antrum of the stomach. It runs medially along the greater curvature Available with the Gray’s Anatomy e-book
in the upper part of the gastrocolic omentum. Just proximal to the
pylorus, it passes posteriorly to drain into the superior mesenteric vein
INNERVATION
below the neck of the pancreas. The right gastroepiploic vein may
receive the right colic vein (forming a ‘gastrocolic trunk’) and/or supe-
rior pancreaticoduodenal vein close to its entry into the superior The stomach is innervated by sympathetic and parasympathetic nerves.
mesenteric vein (Yamaguchi et al 2002). A variety of neurotransmitters have been identified within pyloric
muscle, including acetylcholine, nitric oxide, enkephalins and vasoac-
left gastric vein tive intestinal polypeptide. Inhibition of the sphincter is mediated by
The left gastric vein drains the upper body and fundus of the stomach. nitrergic fibres whilst basal tone is mostly cholinergic (although it
It ascends along the lesser curvature to the oesophageal opening, where should be noted that many other factors, including acid and luminal
it receives several lower oesophageal veins. It then curves posteriorly nutrients, influence pyloric contraction; Ramkumar and Schulze (2005)).
and medially behind the posterior peritoneal surface of the lesser sac,
Sympathetic innervation
passing either anterior or posterior to the common hepatic artery. It
usually drains into the portal vein at the level of the upper border of The sympathetic supply to the stomach originates from the fifth to
the first part of the duodenum, which corresponds to 1–2 cm from the twelfth thoracic spinal segments, and is mainly distributed via the
origin of the portal vein (Rebibo et al 2012). In up to one-third of greater and lesser splanchnic nerves and the coeliac plexus. Peri-arterial
individuals, the left gastric vein terminates in the splenic vein. On rare plexuses form along the arteries arising from the coeliac trunk. Addi-
occasions, it drains into the left portal vein within the liver (Ohkubo tional innervation comes from fibres of the hepatic plexus, which pass
2000), which may be clinically important in portal hypertension. to the upper body and fundus via the lesser omentum and by direct
branches from the greater splanchnic nerves.
Right gastric vein Sympathetic activity causes vasoconstriction, inhibits gastric motility
The right gastric vein is typically small and runs along the medial end and constricts the pylorus. Afferent sensory pathways, including pain,
of the lesser curvature, passing under the peritoneum as it is reflected travel with sympathetic efferent nerves.
from the posterior aspect of the pylorus and first part of the duodenum
Parasympathetic innervation
on to the posterior wall of the lesser sac. It drains directly into the portal
vein at the level of the first part of the duodenum. It receives the pre- The parasympathetic supply to the stomach is from the vagus nerves
pyloric vein as it ascends anterior to the pylorus at the level of the (Fig. 64.15). The anterior vagal trunk (formed mainly from fibres from
pyloric opening. Rarely, the right gastric vein drains directly into a the left vagus nerve within the oesophageal plexus) is often double or
branch of the portal vein within the liver. even triple, and supplies filaments to the cardiac orifice. The nerve is
closely applied to the anterior surface of the outer muscle of the abdom-
posterior gastric veins inal oesophagus and usually divides near the gastro-oesophageal junc-
One or more distinct posterior gastric veins may be present, draining tion into gastric, pyloric and hepatic branches (Jackson 1949). Upper
the middle of the posterior surface of the stomach into the splenic vein. gastric branches radiate on the anterior surface of the upper body and
They may become particularly prominent in portal hypertension fundus but the main gastric branch (also known as the anterior nerve
(Kimura et al 1990). of the lesser curvature or greater anterior gastric nerve) lies in the lesser
omentum near the lesser curvature. It supplies branches to the body
oesophageal and gastric varices and antrum, and usually terminates near the angular incisure in a crow’s
Blood from the oesophageal mucosa normally drains into a submu- foot type of pattern (Shanthi and Sudhayesshayyan 2011). The hepatic
cosal venous plexus, then into a deeper intrinsic venous plexus and branch runs almost transversely between the peritoneal layers of the
finally into peri-oesophageal veins via perforating veins. In the abdomi- lesser omentum towards its free edge to reach the hilum of the liver,
nal oesophagus, the perforating veins drain into tributaries of the left where hepatic branches ramify. From here, some fibres descend adjacent
gastric vein, whereas, in the lower thoracic oesophagus, they drain into to the hepatic artery to supply the pylorus, duodenum and pancreas.
tributaries of the azygos and hemiazygos systems. Bidirectional flow is An additional pyloric branch often arises from the greater anterior
possible in this region, and accommodates pressure changes that occur gastric nerve during its course; this runs inferomedially to the pyloric
during breathing and Valsalva manœuvres. antrum, where it gives off branches to the pylorus before running supe-
Oesophageal and gastric varices are abnormally dilated veins that riorly to contribute to the hepatic plexus. Variations in the anterior
occur in the submucosal plexus of the distal oesophagus and gastric nerve include accessory pyloric branches and high and low courses of
fundus when portal venous pressure is chronically elevated (typically the hepatic and pyloric branches in the lesser omentum.
greater than 15 mmHg). This may develop as a consequence of liver The posterior vagal trunk usually lies within loose connective tissue
fibrosis or cirrhosis, or portal vein thrombosis, or from a variety of other immediately posterior and to the right of the oesophagus. It divides
causes. Portal hypertension leads to the recanalization of occluded into gastric branches and one or more coeliac branches. Gastric branches
embryonic venous channels between venous tributaries of the portal run behind the cardiac orifice and body of the stomach and extend to
system and the systemic venous circulation (e.g. the ligamentum teres) the proximal antrum, but do not normally reach the pyloric sphincter.
and progressive dilation of small, naturally occurring venous anasto- The largest gastric branch (also known as the posterior nerve of the
moses between portal and systemic venous tributaries (Paquet 2000). lesser curvature or the greater posterior gastric nerve) descends posteri-
Valves within these veins become incompetent, permitting retrograde orly near the lesser curvature. The coeliac branch arises from the poste-
flow and causing the development of varices. Varices in the distal rior vagal trunk and carries the majority of fibres contributing to the
oesophagus are readily visible at endoscopy because they are situated coeliac plexus. One or two small hepatic branches may also originate
superficially and protrude into the oesophageal lumen (Fig. 64.13); from the coeliac division of the nerve.
they are vulnerable to rupture and a source of major gastrointestinal The parasympathetic nerve supply is secretomotor to the gastric
bleeding. Gastric varices may also be present on the inferior aspect of mucosa and motor to the gastric musculature. It is responsible for
the cardiac orifice. coordinated relaxation of the pyloric sphincter during gastric emptying.
However, the majority of fibres within the vagus nerves are afferent;
Lymphatic drainage these convey gut sensation, including fullness, nausea and probably
pain.
The stomach has a rich network of lymphatics that connect with lym- Referred pain
phatics draining other viscera within the upper abdomen. At the gastro-
Pain sensation from the stomach is poorly localized and, in common
oesophageal junction, the lymphatics are continuous with those
with other structures of foregut origin, is referred to the epigastrium.
draining the lower oesophagus; in the region of the pylorus, they are
Pain arising from the gastro-oesophageal junction is commonly referred
continuous with those draining the duodenum and pancreas. In
to the lower retrosternal and subxiphoid areas.
general, lymphatics follow the course of the arteries supplying the
stomach. However, many separate groups of nodes are now recognized
(Fig. 64.14) and their relationship to the specific regions and vascular MICROSTRUCTURE
territories of the stomach is of great importance during resection of the
stomach, particularly for malignancy. Pancreatic and hepatic lymphatics The gastric wall consists of the major layers found elsewhere in the gut,
play a significant role in draining the stomach during disease. i.e. mucosa, submucosa, muscularis externa and serosa, together with | 1,549 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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A B C
Fig. 64.13 The endoscopic appearance of oesophageal and gastric varices in portal hypertension. A, Oesophageal varices. B, Fundal varices seen
from within the stomach after retroflexion of the gastroscope. C, Portal gastropathy (gastric antrum) due to venous congestion of the gastric mucosa.
(Courtesy of Professor Mark Stringer.)
Surgery for gastro-oesophageal malignancy involves varying degrees of (wider-draining nodes, including para-aortic nodes). Gastrectomies can
radical resection of lymph nodes that drain the tumour. Locoregional be classified according to the node groups excised with the tumour: D1
lymphatic spread can occur in the absence of haematogenous spread (removal of the affected portion of the stomach and en bloc resection
and gastric cancer may therefore remain a localized disease, even when of N1 nodes); D2 (total gastrectomy, including all N1 and N2 nodes);
lymph nodes are involved (UICC et al 1997). Hence, gastrectomy with and D3 (total gastrectomy plus extensive lymphadenectomy that
meticulous lymphadenectomy can be curative in a proportion of includes the associated upper abdominal lymph nodes: namely, pan-
patients with gastric cancer and nodal involvement. creatic, superior mesenteric, coeliac, hepatic and transverse colic) (Japa-
The extent of potential/actual nodal involvement by the tumour is nese Gastric Cancer Association 1998, Japanese Research Society for
classified as N1 (locoregional nodes specific to the tumour site); N2 Gastric Cancer 1998).
(regional and major named vessel nodes draining the tumour); and N3 | 1,550 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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A
Lesser curvature nodes
Right paracardial nodes Left paracardial nodes
Left gastric nodes
Short gastric arteries
Left gastric artery
Coeliac trunk
Coeliac nodes
Common hepatic nodes
Common hepatic artery
Short gastric
Right gastric artery nodes
Hepatic artery
Suprapyloric
nodes
Gastroduodenal
artery
Left gastroepiploic artery
Splenic artery
Inferior Left gastroepiploic nodes
pancreaticoduodenal
artery
Infrapyloric nodes
Right gastroepiploic nodes
Right gastroepiploic artery
Superior mesenteric artery
Right gastroepiploic nodes
B
Coeliac trunk Left gastric artery
Common hepatic artery Splenic artery
Common hepatic nodes Splenic nodes
Hepatic artery
Hepatoduodenal nodes
Short gastric
Gastroduodenal artery arteries
Splenic hilar nodes
Left gastroepiploic
Retropancreatic artery
nodes
Left gastroepiploic
Anterior pancreatic nodes
nodes Inferior pancreatic nodes
Common hepatic
Superior mesenteric artery Common hepatic
nodes nodes
Pancreas
Superior mesenteric Retropancreatic Portal vein
vein nodes
Superior mesenteric Right gastroepiploic vein
artery
Infrapyloric nodes
Superior mesenteric nodes
Superior mesenteric vein
Fig. 64.14 The main lymph node stations of the stomach (A) and upper abdominal viscera (B). The sagittal relationships of the node groups around the
neck of the pancreas are shown bottom right. The para-aortic nodes are among the highest nodes for these viscera but have been removed for clarity. | 1,551 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Posterior vagus Anterior vagus cuboidal in shape, and their nuclei are rounded and euchromatic. They
contain secretory zymogen granules and their abundant cytoplasmic
A RNA renders them strongly basophilic. Parietal (oxyntic) cells are the
source of gastric acid and of intrinsic factor, a glycoprotein necessary
Hepatic nerves
for the absorption of vitamin B . They are large, oval and strongly
12
eosinophilic, and have centrally placed nuclei.
Parietal cells occur intermittently along the walls of the more apical
Anterior half of the gland but can reach as far as the isthmus; they bulge laterally
gastric nerves
into the surrounding connective tissue. They have a unique ultrastruc-
ture related to their ability to secrete hydrochloric acid. The luminal
Coeliac nerves Greater posterior side of the cell is deeply invaginated to form a series of blind-ended
gastric nerve channels (canaliculi) that bear numerous irregular microvilli covered
B by a plasma membrane rich in H+/K+ ATPase antiporter channels. The
Greater anterior latter actively secrete hydrogen ions into the lumen; chloride ions
gastric nerve follow along the electrochemical gradient. The mitochondria-rich cyto-
plasm facing these channels contains a tubulo-vesicular system of abun-
dant fine membranous tubules directed towards the canalicular surface.
The precise structure of the cell varies with its secretory phase: when
stimulated, the number and surface area of the microvilli increases up
to five-fold, probably as a result of the rapid fusion of the tubulo-
Pyloric nerves vesicular system with the plasma membrane. This process is reversed at
the end of stimulated secretion, when the excess membrane retreats
Pyloric branches back into the tubulo-alveolar system and microvilli are lost.
Fig. 64.15 The distribution of the vagal nerves to the stomach. The two Mucous neck cells are numerous at the necks of the glands and are
most common variations in the anterior vagus are shown in pink. Key: scattered along the walls of the more basal regions. They are typical
A, multiple main trunks; B, low origin of the hepatic/pyloric branch lying mucus-secreting cells, displaying apical secretory vesicles, containing
close to the lesser curvature. mucins, and basally displaced nuclei; their products are distinct histo-
chemically from those of the superficial mucous cells.
Stem cells are relatively undifferentiated mitotic cells from which the
other types of gland cell are derived. They are relatively few in number,
gastric vessels and nerves (Figs 64.16–64.17). The microstructure
and are situated in the isthmus of the gland and the bases of the gastric
reflects the functions of the stomach as an expandable muscular sac
pits. Stem cells are columnar and possess a few short apical microvilli.
lined by secretory epithelium, although there are local structural and
They periodically undergo mitosis; their progeny migrate either apically,
functional variations in this pattern.
to differentiate into new surface mucous cells, or basally, to form
mucous neck, parietal, chief or neuroendocrine cells. All of these cells
Mucosa
have a limited lifespan, especially the mucus-secreting types, and so
they are constantly replaced. The typical replacement period for surface
The mucosa is a thick layer with a soft, smooth surface that is mostly mucous cells is 3 days, and that for mucous neck cells is 1 week. Other
reddish brown in life but pink in the pyloric region. In the contracted cell types appear to live much longer.
stomach, the mucosa is folded into numerous folds, or rugae, most Neuroendocrine (enteroendocrine) cells occur in all types of gastric
of which are longitudinal. They are most marked towards the pyloric gland but more frequently in the body and fundus of the stomach. They
end and along the greater curvature. The rugae represent large folds in are situated mainly in the deeper parts of the glands, among the chief
the submucosal connective tissue (see below) rather than variations in cells. They are basally situated, pleomorphic cells and display irregular
the thickness of the mucosa covering them, and they are obliterated nuclei surrounded by granular cytoplasm that contains clusters of large
when the stomach is distended. As elsewhere in the gut, the mucosa is (0.3 µm) secretory granules. Neuroendocrine cells synthesize a number
composed of a surface epithelium, lamina propria and muscularis of biogenic amines and polypeptides that are important in the control
mucosae. of gut motility and glandular secretion. They are part of the system of
dispersed neuroendocrine cells. In the stomach, they include gastrin-
Epithelium producing G cells; somatostatin-producing D cells; histamine-producing
ECL (enterochromaffin-like) cells; serotonin-producing enterochromaf-
When viewed microscopically at low magnification, the internal surface fin cells; and ghrelin-producing P/D(1)-type endocrine cells (Sakata
of the stomach wall appears honeycombed by small, irregular gastric and Sakai 2010).
pits: there are approximately 60 to 100 gastric pits per square millimeter
of gastric mucosa, each pit having a diameter of approximately 70 µm Cardiac glands
and a depth of about 0.2 mm (Lillibridge 1964) (see Figs 64.16–64.17). Cardiac glands are confined to a small area near the cardiac orifice;
The base of each gastric pit receives several long, tubular gastric glands some are simple tubular glands, others are compound branched tubular
that extend deep into the lamina propria as far as the muscularis mu- glands. Mucus-secreting cells predominate; parietal and chief cells are
cosae. Simple columnar mucus-secreting epithelium covers the entire present but sparse.
luminal surface, including the gastric pits, and is composed of a con-
tinuous layer of surface mucous cells that release gastric mucus from Pyloric glands
their apical surfaces to form a thick, protective, lubricant layer over the Pyloric glands empty via groups of two or three short, convoluted tubes
gastric lining. This epithelium commences abruptly at the Z line at the into the bases of the deep gastric pits of the pyloric antrum; the pits
cardiac orifice, where there is a sudden transition from oesophageal occupy about two-thirds of the mucosal depth (Fig. 64.18). The glands
stratified squamous epithelium. are populated mainly by mucus-secreting cells but they also contain
neuroendocrine cells, especially G cells, which secrete gastrin when
gastric glands
activated by appropriate mechanical stimulation (causing increased
Although all gastric glands are tubular, they vary in form and cellular gastric motility and secretion of gastric juices). Although parietal and
composition in different parts of the stomach. They can be divided into chief cells are scarce, parietal cells are always present in both fetal and
three groups: cardiac, principal and pyloric. The most highly specialized postnatal pyloric glands, and may also appear in the duodenal mucosa,
are the principal glands. proximally near the pylorus, in adult tissue.
Principal gastric glands Lamina propria
The principal glands are found in the body and fundus, three to seven The lamina propria forms a connective tissue framework between the
opening into each gastric pit. Their junction with the base of the pit is glands. It contains small masses of lymphoid tissue, gastric lymphatic
the isthmus; immediately basal to this is the neck; and the remainder follicles, which resemble solitary intestinal follicles (especially in early
is the base. The walls of the gland contain at least five distinct cell types: life). It also contains a complex periglandular vascular plexus involved
chief, parietal, mucous neck, stem and neuroendocrine. in the maintenance of the mucosal environment, e.g. the removal of
Chief (peptic) cells (see Fig. 64.16) are the source of the digestive bicarbonate produced in the tissues as a counterpart to acid secretion,
enzymes pepsin and lipase. They are usually basal in position and and neural plexuses rich in both sensory and motor terminals. | 1,552 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Fundus
Oesophagus
Cardiac orifice
Body Surface mucous cell
Pylorus
Duodenum
Mucus
Pyloric canal
Pyloric antrum
Mucous neck cell
Mucus
Parietal cell
H+
Gastric pit
Intrinsic
factor
Cl−
Chief cell
Isthmus
(neck)
Mucosa
Gastric gland Pepsin
(body)
Neuroendocrine cell
Base
G cells – gastrin
D cells – somatostatin
ECL cells– histamine
Fig. 64.16 Principal regions of the interior of the stomach and the microstructure of tissues and cells within its wall. Undifferentiated, dividing cells are
shown in white. Abbreviations: ECL, enterochromaffin-like.
Muscularis mucosae variably developed in different regions of the stomach and not easily
separated. Clasp-like semicircular smooth muscle fibres are present on
The muscularis mucosae is a thin layer of smooth muscle fibres lying
the right side of the oesophagus and sling-like oblique gastric muscle
external to the layer of glands, arranged as continuous inner circular
fibres on the left side; the latter radiate horizontally towards the greater
and outer longitudinal layers, and a discontinuous external circular
curvature and maintain the angle between the oesophagus and stomach.
layer. The inner layer sends strands of smooth muscle cells between the
The circular muscle layer is thicker in the distal pyloric antrum, where
glands; their contraction probably assists in emptying into the gastric
it forms the anular pyloric sphincter. The outer longitudinal layer is
pits.
most pronounced in the upper two-thirds of the stomach.
Submucosa The muscularis externa enables the stomach to produce churning
movements that mix food with the gastric secretions. When the muscles
contract, they reduce the volume of the stomach and throw the mucosa
The submucosa is a variable layer of loose connective tissue. It contains
into longitudinal folds or rugae (see above). Muscle activity is control-
thick bundles of collagen, numerous elastin fibres, blood vessels and
led by a network of unmyelinated autonomic nerve fibres and their
nervous plexuses, including the ganglionated submucosal (Meissner’s)
ganglia, which lie between the muscle layers in the myenteric (Auer-
plexus.
bach’s) plexus.
Muscularis externa
Interstitial cells of Cajal
The muscularis externa is a thick muscle coat immediately under the
serosa, with which it is closely connected by subserous loose connective Like smooth muscle elsewhere in the gut, interstitial cells of Cajal are
tissue. From innermost outwards, it contains oblique, circular and lon- present within the submucosa and muscular layers of the stomach.
gitudinal layers of smooth muscle fibres (see Fig. 64.6). The layers are These spindle-shaped cells contact nerve fibres and form gap junctions | 1,553 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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E
P
P
Fig. 64.17 A low-power micrograph showing the stomach wall, thrown
into longitudinal folds or rugae that are visible macroscopically. The E
surface epithelium is infolded microscopically to form gastric pits. Gastric
glands extend through the thickness of the mucosal lamina propria and
Fig. 64.18 A micrograph showing the pyloric region of the stomach.
open into the bases of the gastric pits. A muscularis mucosae layer and
Pyloric glands are stained with the periodic acid–Schiff (PAS) technique to
submucosa follow the contours of the rugae. Part of the external
show mucin (magenta) in the gastric pits and glands. Pale-staining cells
muscularis layers is seen below left. (Courtesy of Mr Peter Helliwell and
are the larger parietal cells (P) and smaller enteroendocrine cells (E).
the late Dr Joseph Mathew, Department of Histopathology, Royal
(Courtesy of Dr JB Kerr, Monash University with permission from Kerr JB
Cornwall Hospitals Trust, UK.)
1999 Atlas of Functional Histology. London: Mosby.)
with smooth muscle cells, consistent with their role in modulating
GASTRIC MOTILITY
motor neurotransmission. Interstitial cells of Cajal are involved in the
generation of rhythmic gastric slow-wave contractions and play an
important role in gastric motility. They have been implicated in the In simple terms, the proximal region of the stomach (fundus and upper
pathogenesis of gastric motility disorders such as diabetic gastric paresis body) functions mostly as a temporary storage compartment, regulating
(Negreanu et al 2008) and in the development of gastric stromal intragastric pressure and the onward passage of chyme into the distal
tumours (Roggin and Posner 2012). stomach. Proximal gastric tone decreases with swallowing (receptive
relaxation) and in response to gastric distension (gastric accommoda-
Serosa or visceral peritoneum tion). Its activity is modulated by enterogastric reflexes (e.g. acid,
protein or fat in the duodenum inhibits proximal gastric muscle con-
traction) and gut hormones (e.g. cholecystokinin, gastrin, glucagon and
The serosa is an extension of the visceral peritoneum. It covers the entire
vasoactive intestinal polypeptide). The vagus nerve plays a key role in
surface of the stomach other than along the attachments of the greater
these reflexes. In contrast to this activity, the muscle of the distal region
and lesser omenta to the greater and lesser curvatures, respectively,
of the stomach exhibits strong phasic contractions that increase in
where the peritoneal layers are separated by vessels and nerves, and over
amplitude towards the pylorus; these occur about three times per
a small posterosuperior area near the cardiac orifice, where the stomach
minute and act to grind the food mechanically and propel it towards
contacts the diaphragm at the reflections of the gastrophrenic and left
the pylorus. Solid material lags behind liquids, and when the contents
gastropancreatic folds.
of the antrum reach the contracted pylorus, only the liquid and small
particulate solids can be expelled into the duodenum; larger solid
Endoscopic mucosal resection
matter is retropulsed back into the stomach for further breakdown
(Patrick and Epstein 2008).
Endoscopic mucosal resection (EMR) is a technique that can be applied
in the oesophagus and stomach in order to excise dysplastic lesions or
early cancers that remain confined to the mucosa (Pech et al 2008).
Bonus e-book images
EMR is a misnomer since the technique involves resection of both the
mucosa and submucosa. The technique is inappropriate for tumours
that have invaded the submucosa since these are associated with a
significant risk of lymph node metastases and therefore require formal Fig. 64.13 The endoscopic appearance of oesophageal and gastric
surgical resection (oesophagectomy or gastrectomy) and lymphadenec- varices in portal hypertension.
tomy (Ancona 2008).
KEY REFERENCES
Ancona E, Rampado S, Cassaro M et al 2008 Prediction of lymph node status A study that demonstrated that reflux of gastric acid and bile have a
in superficial esophageal carcinoma. Ann Surg Oncol 15:3278–88. synergistic effect in the pathogenesis of Barrett’s oesophagus.
A study that reported that intramucosal cancers and those invading the
García RM, Tomás NP, Pozo CD et al 2013 Laparoscopic treatment of acute
upper third of the submucosa are associated with significantly fewer nodal
gastric volvulus. Cir Esp 91:189–93.
metastases than tumours invading deeper into the submucosa. This
A case series that included 10 patients with acute gastric volvulus treated by
demonstrated the potential for endoscopic treatment of superficial lesions
laparoscopic gastropexy. The technique was shown to be safe and effective in
and the need for oesophagectomy and lymphadenectomy where there is
the emergency setting.
invasion beyond the upper third of the submucosa.
Japanese Research Society for Gastric Cancer 1998 Japanese Classification
Dvorak K, Payne CM, Chavarria M et al 2007 Bile acids in combination with
of Gastric Carcinoma. Tokyo: Kanehara; Gastric Cancer 1:10–24,
low pH induce oxidative stress and oxidative DNA damage: relevance
25–30.
to the pathogenesis of Barrett’s oesophagus. Gut 56:763–71. | 1,554 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Key references
A detailed, widely accepted description of the lymph node fields of the upper Pech O, Behrens A, May A et al 2008 Long-term results and risk factor analy-
abdominal viscera, particularly in relation to malignancy. sis for recurrence after curative endoscopic therapy in 349 patients with
high-grade intraepithelial neoplasia and mucosal adenocarcinoma in
Mittal RK, Goyal RK 2006 Sphincter mechanisms at the lower end of the
Barrett’s oesophagus. Gut 57:1200–6.
esophagus. PART 1 Oral cavity, pharynx and esophagus. GI Motility
A paper that showed that endoscopic therapy (endoscopic resection and
online. doi:10.1038/gimo14.
photodynamic therapy) was safe and highly effective at treating patients
A review that discusses the principle anatomical mechanisms that prevent
with high-grade dysplasia and intramucosal (T1a) cancer associated with
reflux at the gastro-oesophageal junction and explains how failure of one or
Barrett’s oesophagus.
more of these may lead to progressive gastro-oesophageal reflux disease.
Silverstein FE, Tytgat GNJ 1991 Atlas of Gastrointestinal Endoscopy, 2nd ed.
Paquet KJ 2000 Causes and pathomechanisms of oesophageal varices devel- New York: Gower Medical Publishing.
opment. Med Sci Monit 6:915–28. A pictorial atlas that includes over 900 endoscopic images along the entire
An explanation of how chronic liver diseases cause a pathological increase length of the gastrointestinal tract. The accompanying text discusses normal
in portal pressure, leading to the development of portosystemic collaterals, and abnormal features and therapeutic techniques.
including oesophageal varies. This article reviews the pathogenesis, diagnosis
Yousef F, Cardwell C, Cantwell MM et al 2008 The incidence of esophageal
and treatment of oesophageal varices.
cancer and high-grade dysplasia in Barrett’s oesophagus: A systematic
Paterson WG 2001 The normal anti-reflux mechanism. Chest Surg Clin N review and meta-analysis. Am J Epidemiol 168:237–49.
Am 11:473–83. A systematic review and meta-analysis that evaluated the incidence of
An article that describes the normal mechanisms that prevent reflux of oesophageal cancer and high-grade dysplasia in Barrett’s oesophagus,
gastric contents into the oesophagus, including the resting tone of the lower concluded that the risk of neoplastic progression was lower than previously
oesophageal sphincter, the mechanical effect of the crural sling, and the described, and questioned the need for routine surveillance of all patients
specialized anatomy of the proximal stomach. with non-dysplastic Barrett’s oesophagus. | 1,555 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Abdominal oesophagus and stomach
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demonstrated the potential for endoscopic treatment of superficial lesions
An explanation of how chronic liver diseases cause a pathological increase
and the need for oesophagectomy and lymphadenectomy where there is
in portal pressure, leading to the development of portosystemic collaterals,
invasion beyond the upper third of the submucosa.
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Arul GS, Parikh D 2008 Oesophageal replacement in children. Ann R Coll and treatment of oesophageal varices.
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Csendes A, Burgos AM 2005 Size, volume and weight of the stomach in gastric contents into the oesophagus, including the resting tone of the lower
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Didio LJ, Anderson MC 1968 The ‘Sphincters’ of the Digestive System. Bal- Patrick A, Epstein O 2008 Review article: gastroparesis. Aliment Pharmacol
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Dvorak K, Payne CM, Chavarria M et al 2007 Bile acids in combination with Pech O, Behrens A, May A et al 2008 Long-term results and risk factor analy-
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to the pathogenesis of Barrett’s oesophagus. Gut 56:763–71. high-grade intraepithelial neoplasia and mucosal adenocarcinoma in
A study that demonstrated that reflux of gastric acid and bile have a Barrett’s oesophagus. Gut 57:1200–6.
synergistic effect in the pathogenesis of Barrett’s oesophagus. A paper that showed that endoscopic therapy (endoscopic resection and
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García RM, Tomás NP, Pozo CD et al 2013 Laparoscopic treatment of acute
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gastric volvulus. Cir Esp 91:189–93.
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laparoscopic gastropexy. The technique was shown to be safe and effective in Piasecki C 1974 Blood supply to the human gastroduodenal mucosa with
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Hershcovici T, Mashimo H, Fass R 2011 The lower esophageal sphincter. Preiksaitis HG, Diamant NE 1997 Regional differences in cholinergic activ-
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Japanese Gastric Cancer Association 1998 Japanese classification of gastric
carcinoma – 2nd English edition. Gastric Cancer 1:10–24. Rebibo L, Chivot C, Fuks D et al 2012 Three-dimensional computed tomo-
Japanese Research Society for Gastric Cancer 1998 Japanese Classification of graphy analysis of the left gastric vein in a pancreatectomy. HPB (Oxford)
Gastric Carcinoma. Tokyo: Kanehara; Gastric Cancer 1:10–24, 25–30. 14:414–21.
A detailed, widely accepted description of the lymph node fields of the upper Roggin KK, Posner MC 2012 Modern treatment of gastric gastrointestinal
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Kimura K, Ohto M, Matsutani S et al 1990 Relative frequencies of portosys- Roman S, Kahrilas PJ 2014 The diagnosis and management of hiatus hernia.
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Kwok H, Marriz Y, Al-Ali S et al 1999 Phrenoesophageal ligament revisited. Shanthi KC, Sudhayesshayyan D 2011 Branching pattern of the anterior
Clin Anat 12:164–70. nerve of Latarjet and its clinical significance. J Clin Diagn Res 5:
Liebermann-Meffert D, Lüscher U, Neff U et al 1987 Esophagectomy without 980–3.
thoracotomy: is there a risk of intramediastinal bleeding? A study on Silverstein FE, Tytgat GNJ 1991 Atlas of Gastrointestinal Endoscopy, 2nd ed.
blood supply of the esophagus. Ann Surg 206:184–92. New York: Gower Medical Publishing.
Lillibridge CB 1964 The fine structure of the normal human gastric mucosa. A pictorial atlas that includes over 900 endoscopic images along the entire
Gastroenterology 47:269–90. length of the gastrointestinal tract. The accompanying text discusses normal
and abnormal features and therapeutic techniques.
Loukas M, Wartmann CT, Louis RG Jr et al 2007 The clinical anatomy of the
posterior gastric artery revisited. Surg Radiol Anat 29:361–6. Stein HJ, Liebermann-Meffert D, DeMeester TR et al 1995 Three-dimensional
Mackintosh CE, Kreel L 1977 Anatomy and radiology of the areae gastricae. pressure image and muscular structure of the human lower esophageal
Gut 18:855–64. sphincter. Surgery 117:692–8.
Mirjalili SA, Hale SJ, Buckenham T et al 2012 A reappraisal of adult thoracic UICC, Sobin LH, Wittekind CH (eds) 1997 TNM classification of malignant
surface anatomy. Clin Anat 25:827–34. tumours, 5th ed. Berlin: Springer.
Mittal RK, Goyal RK 2006 Sphincter mechanisms at the lower end of Yamagami T, Terayama K, Yoshimatsu R et al 2010 Embolisation of the right
the esophagus. PART 1 Oral cavity, pharynx and esophagus. GI Motility gastric artery in patients undergoing hepatic arterial infusion chemo-
online doi: 10.1038/gimo14. therapy using two possible approach routes. Br J Radiol 83:578–84.
A review article that discusses the principle anatomical mechanisms that Yamaguchi S, Kuroyanagi H, Milson JW et al 2002 Venous anatomy of the
prevent reflux at the gastro-oesophageal junction and explains how failure of right colon: precise structure of the major veins and gastrocolic trunk
one or more of these may lead to progressive gastro-oesophageal reflux in 58 cadavers. Dis Colon Rectum 45:1337–40.
disease. Yousef F, Cardwell C, Cantwell MM et al 2008 The incidence of esophageal
Ndoye JM, Dia A, Ndiaye A et al 2006 Arteriography of three models of cancer and high-grade dysplasia in Barrett’s oesophagus: A systematic
gastric oesophagoplasty: the whole stomach, a wide gastric tube and a review and meta-analysis. Am J Epidemiol 168:237–49.
narrow gastric tube. Surg Radiol Anat 28:429–37. A systematic review and meta-analysis that evaluated the incidence of
oesophageal cancer and high-grade dysplasia in Barrett’s oesophagus,
Negreanu LM, Assor P, Mateescu B et al 2008 Interstitial cells of Cajal in the
concluded that the risk of neoplastic progression was lower than previously
gut – a gastroenterologist’s point of view. World J Gastroenterol 14:
described, and questioned the need for routine surveillance of all patients
6285–8.
with non-dysplastic Barrett’s oesophagus. | 1,556 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
CHAPTER
65
Small intestine
OVERVIEW
A
The small intestine consists of the duodenum, jejunum and ileum. It 1st
extends from the distal end of the pyloric canal to the ileocaecal junc-
tion and has a mean length of 5 metres (3–8.5 metres) when measured
intraoperatively in the living adult (Teitelbaum et al 2013). The duode-
num extends from the stomach to the duodenojejunal junction. The 2nd
remaining small intestine is often referred to as the ‘small bowel’, the
proximal two-fifths of which is referred to as the jejunum and the distal
three-fifths as the ileum. There is no clear boundary between the two
parts, but there is a gradual transition in morphology from the proximal 4th
to distal ends of the small bowel. The distal 30 cm or so of the ileum
is often referred to as the terminal ileum, which has some specialized
3rd
physiological functions.
The duodenum is in the upper abdomen and is mostly retroperito-
neal. The jejunum and ileum occupy the central and lower parts of the
abdominal cavity and usually lie within the boundary formed by the
colon. The small bowel is attached to the posterior abdominal wall by
B
a mesentery that allows the intestinal loops to be mobile. In the supine Neck of
position, loops of jejunum may be found anterior to the transverse gallbladder
colon, stomach and even lesser omentum, whereas in the erect position,
Quadrate lobe
loops of ileum may descend into the pelvis anterior to the rectum. The
greater omentum covers the upper jejunum and ileum to a variable Right end of the
extent. The jejunum and ileum are covered by visceral peritoneum on Hepatic gastrocolic omentum
flexure
all but their mesenteric borders, where the peritoneum is reflected to
enclose the adipose tissue of the mesentery. The small bowel mesentery Attachment of the
transverse mesocolon
abuts about 20% of the circumference of the muscular wall of the ileum
and somewhat less of the jejunum.
DUODENUM
Superior
mesenteric artery
The adult duodenum is approximately 25 cm long and is the shortest,
widest and most predictably placed part of the small intestine. The Superior
proximal 2.5 cm is intraperitoneal and the remainder is retroperitoneal. mesenteric vein
The duodenum forms an elongated ‘C’ that lies between the level of the
C
first and third lumbar vertebrae in the supine position. The lower ‘limb’
Common hepatic
of the C extends further to the left of the midline than the upper limb. duct
The head and uncinate process of the pancreas lie within the concavity Portal vein Gastroduodenal
of the duodenum, which is ‘draped’ over the prominence formed artery
by the lumbar spine; the duodenum therefore curves in an anteropos- Right kidney Left kidney
terior direction as well as forming a ‘C’. The duodenum lies entirely
above the level of the umbilicus. It is described as having four parts
(Fig. 65.1).
FIRST (SUPERIOR) PART
The first, and most mobile, part of the duodenum is about 5 cm long.
It starts at the duodenal end of the pylorus and ends at the superior
duodenal flexure. The proximal 2.5 cm is intraperitoneal while the
distal 2.5 cm is covered by peritoneum on its anterior and superior Left renal
surfaces and forms the inferior boundary of the epiploic foramen. vessels
The lesser omentum is attached to its upper border and the greater
omentum to its lower border. The first 2–3 cm of the duodenum is lined Right renal Left ureter
vessels
by relatively smooth mucosa and readily distends on insufflation during
Aorta
endoscopy. This part is frequently referred to as the duodenal ‘cap’. Right ureter
During contrast radiology, it shows a few longitudinal folds continuous Left gonadal
with the pylorus (Mather Cordiner and Calthrop 1936) and has a tri- Right gonadal vein artery
angular appearance; it is often visible on plain radiographs of the
Right gonadal artery
abdomen as an isolated triangular gas shadow to the right of the first
or second lumbar vertebra. The first part of the duodenum passes supe- Inferior vena cava
riorly, posteriorly and laterally for 5 cm before curving sharply inferi- Fig. 65.1 A, The four parts of the duodenum. B, Anterior relations of the
1124 orly at the superior duodenal flexure. It becomes more retroperitoneal duodenum. C, Posterior relations of the duodenum. | 1,557 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Duodenum
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during this part of its course, until peritoneum only covers its anterior because the anterior surface of the first part is covered only by
aspect. The section from the duodenal cap to the superior duodenal peritoneum.
flexure lies posterior and inferior to the quadrate lobe of the liver. The common hepatic and hepatoduodenal lymph nodes lie close to
Beyond the duodenal cap, the internal appearance is characterized the first part of the duodenum (see Fig. 64.14B) and can be visualized
by circumferential mucosal folds that remain pronounced, even during using endoscopic ultrasound; this may be important in the staging of
endoscopic insufflation (Fig. 65.2). gastric, pancreatic or bile duct tumours. The proximity of the common
The first part of the duodenum lies anterior to the gastroduodenal bile duct to the first part of the duodenum allows endoscopic ultra-
artery, common bile duct and portal vein, and anterosuperior to the sound examination of the distal common bile duct and the formation
head and neck of the pancreas. The gastroduodenal artery lies immedi- of a surgical anastomosis between bile duct and duodenum (choledo-
ately behind the posterior wall of the duodenum; a penetrating peptic choduodenostomy) when required.
ulcer on the posterior wall may erode into the gastroduodenal artery The junction of the first and second parts of the duodenum lies
or one its branches and cause dramatic haemorrhage. A penetrating posterior to the neck of the gallbladder.
peptic ulcer on the anterior wall may perforate into the peritoneal cavity
SECOND (DESCENDING) PART
The second part of the duodenum is approximately 8 cm long. It starts
at the superior duodenal flexure and runs inferiorly in a gentle curve,
convex to the right side of the vertebral column and extending to the
lower border of the third lumbar vertebral body. It then turns sharply
medially at the inferior duodenal flexure, which marks its junction with
the third part of the duodenum. It is covered by peritoneum only on
its upper anterior surface, lies posterior to the gallbladder and the right
lobe of the liver at its start, and is crossed anteriorly by the transverse
colon. The right end of the gastrocolic omentum and the origin of the
transverse mesocolon are attached to the anterior surface of the duode-
num by loose connective tissue. Below the attachment of the transverse
mesocolon, the connective tissue and vessels forming the mesentery of
the upper ascending colon and hepatic flexure are loosely attached to
its anterior surface. This part of duodenum is at risk of injury during
surgical mobilization of the ascending colon and hepatic flexure.
The second part lies anterior to the hilum of the right kidney, the
right renal vessels, the lateral edge of the inferior vena cava and the right
psoas major (see Fig. 65.1C). The head of the pancreas and the common
bile duct are medial and the hepatic flexure is above and lateral. Part of
the pancreatic head is sometimes embedded in the medial duodenal
wall, and pancreatic ‘rests’ in the duodenal wall may produce small
filling defects on contrast radiology. The internal appearance is similar
to that of the distal portion of the first part of the duodenum, with
pronounced mucosal folds (Fig. 65.3). The common bile duct and
pancreatic duct enter the medial wall, where they usually unite to form
a common channel, which frequently contains a dilated segment known
as the hepatopancreatic ampulla (of Vater) (p. 1175). The narrow distal
end of this channel opens on the summit of the major duodenal papilla,
Duodenal cap Duodenojejunal flexure a mucosal elevation situated on the posteromedial wall of the second
Fig. 65.2 The contrast radiographic appearance of the duodenum part, 8–10 cm distal to the pylorus. A duodenal mucosal fold often
showing a distended duodenal cap and the remainder of the duodenum partially encircles the major papilla, forming a hood (Horiguchi and
up to the duodenojejunal flexure. Kamisawa 2010) (see Fig. 65.3). A second, accessory pancreatic duct is
Fig. 65.3 The endoscopic appearance of the
duodenum. A, Duodenal cap (first part). B, Second
part, showing the pronounced, ‘branched’
mucosal folds. C, Major duodenal papilla. D, Third
part.
A B
D
C | 1,558 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
SmAll inTESTinE
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nOiTCES
sometimes present and opens about 2 cm proximal to the major papilla
on a minor duodenal papilla (Suda 2010, Kamisawa et al 2010). Gastroduodenal artery
Duodenal diverticula Supraduodenal artery
Posterior superior
pancreaticoduodenal
The duodenum is the most common site for a diverticulum in the small
artery
intestine. Diverticula are usually solitary and may be congenital (con-
taining all layers of the duodenal wall) or acquired (protrusion of the Anterior superior Right gastroepiploic artery
pancreaticoduodenal
mucosa and submucosa through a defect in the muscular coat of the
artery
bowel wall). They are typically located on the medial wall of the second
Communicating artery
part of the duodenum, intimately related to the head of the pancreas,
and the major duodenal papilla is frequently found either on the
Posterior inferior
mucosal fold at the mouth of a diverticulum or arising from the mucosa pancreaticoduodenal
within it. Diverticula may complicate interpretation of contrast radio- artery
graphs of the duodenum or biliary system, and may cause difficulties
Anterior inferior
during attempted endoscopic cannulation of the major duodenal
pancreaticoduodenal
papilla. Most are asymptomatic but they may be complicated by bleed-
artery
ing, inflammation, perforation and, occasionally, pancreatitis or biliary
Inferior pancreaticoduodenal artery
complications (Fotiades et al 2005). Duodenal branches
First jejunal artery
THIRD (HORIZONTAL) PART
Anterior vessels
Posterior vessels
The third part of the duodenum starts at the inferior duodenal flexure (behind pancreas or duodenum)
and is approximately 10 cm long. It runs from the right side of the lower
Fig. 65.4 The arterial supply of the duodenum. Only representative
border of the third lumbar vertebra, and passes to the left and slightly branches of the small vessels, which may be multiple, are shown.
superiorly, anterior to the inferior vena cava and abdominal aorta,
becoming continuous with the ascending fourth part (see Fig. 65.1C).
It lies posterior to the transverse mesocolon, and is crossed anteriorly
by the origin of the small bowel mesentery and the superior mesenteric
vessels. The lower portion of its anterior aspect is covered by perito- VASCULAR SUPPLY AND LYMPHATIC DRAINAGE
neum, which is reflected anteriorly to form the posterior layer of the
root of the small bowel mesentery. The anterior surface of the left Arteries
end, close to the junction with the fourth part, is also covered by
The main vessels supplying the duodenum are the superior and inferior
peritoneum.
pancreaticoduodenal arteries. The first and second parts also receive
The third part lies anterior to the right ureter, right psoas major, right
contributions from other sources, including the right gastric, supraduo-
gonadal vessels, inferior vena cava and abdominal aorta (at the origin
denal, right gastroepiploic, hepatic and gastroduodenal arteries (Fig.
of the inferior mesenteric artery), and inferior to the head of the pan-
65.4). Branches of the superior pancreaticoduodenal artery may con-
creas. Anteroinferiorly, loops of jejunum lie in the right and left infra-
tribute to the supply of the pyloric canal, anastomosing to a minor
colic compartments. The mid portion of the third part lies in the angle
extent with the gastric arteries within the muscular layer of the
between the superior mesenteric artery anteriorly and the abdominal
pyloroduodenal junction.
aorta posteriorly; narrowing of this angle may occur from loss of
perivascular adipose tissue or spinal straightening and is a rare cause of Gastroduodenal artery
duodenal obstruction (Merrett et al 2009). The gastroduodenal artery usually arises from the common hepatic
artery behind or above the first part of the duodenum. It descends
behind the retroperitoneal portion of the first part of the duodenum to
FOURTH (ASCENDING) PART the left of the common bile duct. At the lower border of the first part
of the duodenum, it is commonly described as dividing into the right
The fourth part of the duodenum is 2.5 cm long. It starts just to the left gastroepiploic and superior pancreaticoduodenal arteries but this ana-
of the aorta, runs superiorly and laterally to the level of the upper tomical arrangement is rare (Bradley 1973, Bertelli et al 1995, Bertelli
border of the second lumbar vertebra, then turns sharply anteroinferi- et al 1996) and its usual branching pattern is as follows. As it descends
orly at the duodenojejunal flexure to become continuous with the behind the first part of the duodenum, it usually gives off the posterior
jejunum. The inferior mesenteric vein lies either posterior to the duo- superior pancreaticoduodenal artery, several retroduodenal branches
denojejunal flexure or at its lateral margin beneath a peritoneal fold. that supply the first part and proximal portion of the second part of the
The duodenojejunal flexure is a useful landmark to locate the vein duodenum, and a supraduodenal artery that supplies the anterosupe-
radiologically or surgically. The aorta, left sympathetic trunk, left psoas rior part of the proximal duodenum (Bianchi and Albanèse 1989). As
major, left renal and left gonadal vessels are all posterior relations, the gastroduodenal artery emerges below the first part of the duode-
the left kidney and left ureter are posterolateral, and the transverse num, it usually gives off the right gastroepiploic artery and several
colon and mesocolon are anterior, separating it from the stomach (see pyloric branches. It then descends on the anterior surface of the pan-
Fig. 62.8). The inferior border of the body of the pancreas is superior. creas, where it divides into the anterior superior pancreaticoduodenal
The peritoneum of the root of the small bowel mesentery descends over artery and pancreatic branches. Although the gastroduodenal artery
its anterior surface. usually branches from the common hepatic artery, it may occasionally
At its left lateral limit, the fourth part becomes progressively invested originate from other sources, including: as a trifurcation with the right
in peritoneum, such that the duodenojejunal flexure is suspended from and left hepatic arteries; the coeliac trunk; the superior mesenteric
the retroperitoneum by a double fold of peritoneum, the suspensory artery; or from the right or left branch of the hepatic artery.
ligament of the duodenum (or ligament of Treitz). The ligament of The gastroduodenal artery or one of its branches may be a source of
Treitz is in two parts; the first part may contain skeletal muscle fibres haemorrhage from a penetrating posterior duodenal ulcer (see above)
and runs from the right crus of the diaphragm to connective tissue or it may be the site of aneurysm or pseudoaneurysm formation; for
around the coeliac trunk, and the second part contains smooth muscle these reasons, it is an important vessel for interventional radiologists.
and descends from connective tissue around the coeliac trunk to the
duodenum, passing behind the pancreas anterior to the left renal vein. Superior pancreaticoduodenal arteries
The ligament is often absent or rudimentary in adults and its function There are usually two superior pancreaticoduodenal arteries: a posterior
is unknown (Kim et al 2008). The ligament of Treitz is avascular; the and anterior. The posterior superior pancreaticoduodenal artery is
vascular supply to the fourth part of the duodenum enters its wall from usually a separate branch of the gastroduodenal artery and is given off
the posteromedial aspect. behind the upper border of the first part of the duodenum. It descends
The duodenojejunal flexure is an important landmark in the radio- to the right, anterior to the portal vein and common bile duct, where
logical diagnosis of incomplete rotation and malrotation of the small the latter lies behind the first part of the duodenum. It then spirals
intestine (p. 1054). around the right side of the bile duct to run behind the head of the | 1,559 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Jejunum
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RETPAHC
pancreas, crosses posterior to the retropancreatic segment of the Lymphatic drainage
common bile duct (which is embedded, to a variable degree, in the
Duodenal lymphatics run to superior and inferior pancreaticoduodenal
head of the pancreas), and anastomoses with the posterior division of
lymph nodes, and from there to supra- and infrapyloric, hepatoduo-
the inferior pancreaticoduodenal artery (Bertelli et al 1996). The pos-
denal, common hepatic, coeliac and superior mesenteric nodes.
terior artery supplies branches to the head of the pancreas, the first and
Lymphatic drainage to para-aortic nodes has also been described (Hirai
second parts of the duodenum, and several branches to the lowest part
et al 2001).
of the common bile duct.
The anterior superior pancreaticoduodenal artery is usually a termi- Duodenal feeding
nal branch of the gastroduodenal artery and descends in the anterior
groove between the second part of the duodenum and the head of the
Available with the Gray’s Anatomy e-book
pancreas or on the anterior surface of the gland parallel to the groove
(Bertelli et al 1995). It supplies branches to the first and second parts
of the duodenum and to the head of the pancreas, and then passes
posteriorly to anastomose with the anterior division of the inferior INNERVATION
pancreaticoduodenal artery.
The duodenum is innervated by both parasympathetic and sympathetic
inferior pancreaticoduodenal artery neurones.
The inferior pancreaticoduodenal artery usually arises from the superior Preganglionic sympathetic neurones have their cell bodies in the
mesenteric artery or its first jejunal branch, near the superior border of intermediolateral columns of the grey matter in the fifth to the twelfth
the third part of the duodenum (Bertelli et al 1996). It crosses behind thoracic spinal segments. Their fibres travel via the greater and lesser
the superior mesenteric vein and passes behind the uncinate process splanchnic nerves to the coeliac plexus and synapse in the coeliac and
of the pancreas, where it divides into anterior and posterior branches. superior mesenteric ganglia; postganglionic axons are distributed to the
The anterior branch passes to the right, immediately inferior and then duodenal wall via peri-arterial plexuses on the branches of the coeliac
anterior to the lower border of the head of the pancreas, and runs trunk and superior mesenteric artery. The sympathetic nerves are vaso-
superiorly to anastomose with the anterior superior pancreaticoduode- constrictor to the duodenal vasculature and inhibitory to duodenal
nal artery. The posterior branch runs posteriorly to the right behind the musculature.
head of the pancreas, and anastomoses with the posterior superior The preganglionic parasympathetic supply is carried by vagal fibres
pancreaticoduodenal artery (Bertelli et al 1997). Both branches supply that travel from the coeliac plexus and synapse on neurones in the
the pancreatic head, its uncinate process, and the second and third parts duodenal wall. The parasympathetic supply is secretomotor to the duo-
of the duodenum. Occasionally, the anterior and posterior branches denal mucosa and motor to the duodenal musculature.
arise separately from the superior mesenteric or first jejunal artery.
Referred pain
Jejunal artery branches In common with other structures derived from the foregut, pain arising
Branches from the first jejunal branch of the superior mesenteric artery from the proximal duodenum is poorly localized and referred to the
supply the fourth part of the duodenum and frequently anastomose epigastrium. It is mediated by afferent fibres that accompany the sym-
with a terminal branch of the anterior superior pancreaticoduodenal pathetic neurones.
artery. The fourth part of the duodenum therefore receives a potential
collateral supply from the coeliac trunk and superior mesenteric artery,
which means that it is not commonly affected by ischaemia.
JEJUNUM
Veins
Submucosal and intramural veins give rise to small veins that accom- The jejunum has an external diameter of about 4 cm and an internal
pany corresponding named arteries. The venous anatomy of this region diameter of about 3 cm. It has a thicker wall than the ileum and a rich
is variable and not well characterized. The superior pancreaticoduode- arterial blood supply. The plicae circulares (see below) are most pro-
nal vein runs superiorly on the posterior surface of the head of the nounced in the proximal jejunum, where they are more numerous
pancreas, posterior to the distal common bile duct, and usually drains and deeper than elsewhere in the small bowel (Figs 65.5–65.6). They
into the portal vein. The inferior pancreaticoduodenal vein runs inferi- frequently ‘branch’ around the lumen and may appear to be stacked
orly and usually drains into the superior mesenteric vein or its first on top of each other, giving the jejunum a characteristic appearance
jejunal tributary. Small veins from the first and upper second parts of during single contrast radiography (see Fig. 65.6), computed tomo-
the duodenum drain directly into the portal vein, and veins from the graphic (CT) enterography (Fig. 65.7A) or magnetic resonance (MR)
third and fourth parts may drain directly into the superior mesenteric enterography (Fig. 65.7B). The plicae circulares are also clearly visible
vein. Numerous small anastomoses are present between veins of the by capsule endoscopy, in which images of the small bowel are transmit-
second and third parts of the duodenum and retroperitoneal veins ted wirelessly from a small swallowed camera that is the size of a pill
(Murakami et al 1999). (Fig. 65.8).
Fig. 65.5 Typical cross-sections through the
Mesentery proximal jejunum (A) and terminal ileum (B). The
Vasa recta mesenteric attachment is wider in the jejunum,
and two leaves of vessels enter the bowel wall.
The latter is also thicker in the jejunum.
Mucosa
Peyer’s patch
Plicae circulares
Submucosal
arterial plexus
Circular muscle
Longitudinal muscle
Serosa
A B | 1,560 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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When gastric emptying is functionally impaired – as, for example, in Superior mesenteric Superior mesenteric Stomach
gastroparesis, nutrition may be delivered directly into the duodenum vein artery
or jejunum via a nasal transpyloric feeding tube.
A
Ileum Jejunum
Stomach Transverse colon
B
Ileum Jejunum
Fig. 65.7 A, Computed tomographic (CT) enterography. Coronal slice
showing small intestinal loops and superior mesenteric vessels.
B, Magnetic resonance (MR) enterography. Coronal slice showing the
small intestine and transverse colon. | 1,561 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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In the supine position, the jejunum usually occupies the upper left Jejunal feeding In patients with a functioning intestine who cannot
infracolic compartment, extending down to the umbilical region. The tolerate adequate oral or intragastric feeding, jejunal feeding is often
first one or two loops often occupy a recess between the left part of the the preferred option. Compared to parenteral (intravenous) nutrition,
transverse mesocolon and the left kidney. On supine radiological exam- enteral feeding is associated with fewer complications. Furthermore, it
ination, the jejunal loops are characteristically situated in the upper maintains the integrity of the gut mucosa (thereby reducing bacterial
abdomen, to the left of the midline, whereas the ileal loops tend to lie translocation from the gut lumen), decreases the likelihood of aspira-
in the lower right part of the abdomen and pelvis. This distribution can tion from gastro-oesophageal reflux, and is less of a stimulus for pan-
be reversed in small bowel obstruction due to rotation of the dilated creaticobiliary secretion. Jejunal feeds can be delivered via a nasojejunal
bowel around its mesenteric attachment. or gastrojejunal tube, or directly into the jejunum; gastrojejunal and
jejunal tubes may be inserted endoscopically, radiologically or surgi-
cally. The end of the feeding tube must lie beyond the duodenojejunal
flexure to prevent reflux of feed into the duodenum and stomach.
ILEUM
The ileum has a median external diameter of about 3 cm, an internal
diameter of about 2.5 cm and tends to have a thinner wall than the
jejunum (see Fig. 65.5B). The plicae circulares become progressively less
obvious in the distal ileum; they tend to be single and flatter (see Figs
65.6–65.7; Fig. 65.9). The mucosa of the terminal ileum immediately
proximal to the ileocaecal junction may appear almost flat at endos-
CC JJ copy, although the villi can be seen when viewed close up (see Fig. 65.9)
JJ and at capsule endoscopy (see Fig. 65.8).
In the supine position, the ileum lies mainly in the hypogastric
II
region and right iliac fossa. The terminal ileum frequently lies in the
JJ
pelvis, from where it ascends over the right psoas major and right iliac
II vessels, to end by opening at the ileocaecal junction in the right iliac
II fossa.
ANATOMICAL DIFFERENCES BETWEEN
THE JEJUNUM AND ILEUM
A
While there is no clear boundary between the jejunum (the proximal
two-fifths of the small intestine beyond the duodenum) and the ileum
(the distal three-fifths), there are general anatomical differences between
these regions. The wall of the jejunum is thicker and more vascular, has
a greater number of more prominent plicae circulares, and contains less
CC
TTII
PPCC
PPCC
II
II
B
Fig. 65.6 Barium studies of the jejunum and ileum. A, Barium follow-
through. The feathery appearance of the small intestine is due to the
plicae circulares and is most prominent in the jejunum. The constrictions
(arrows) are the result of peristalsis. B, Small bowel enema (enteroclysis).
The plicae circulares are clearly demonstrated by this technique.
Abbreviations: C, caecum; I, ileum; J, jejunum; PC, plicae circulares; TI,
terminal part of ileum. Fig. 65.9 The endoscopic appearance of the terminal ileum.
A B C D
Fig. 65.8 The small intestine visualized by capsule endoscopy (PillCam®). A, The proximal jejunum at 1 h 34 mins. B, The distal jejunum at 1 h 51 min.
C, The proximal ileum at 2 h 25 min. D, The distal ileum at 3 h 34 min. Note the presence of plicae circulares and visible intestinal villi. (Courtesy of
Simon Gabe.) | 1,562 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Fig. 65.12 A temporary loop ileostomy in an infant. The skin marking
around the stoma is from the stoma bag adhesive. (Courtesy of Professor
Mark Stringer, Christchurch Hospital, New Zealand.)
Fig. 65.11 A Meckel’s diverticulum containing ectopic mucosa at its tip.
(Courtesy of Professor Mark Stringer, Christchurch Hospital, New
Zealand.)
The mean length of the small bowel, measured from the duodenojeju- Small bowel transplantation has become a standard clinical procedure
nal flexure to the ileocaecal junction in vivo, is about 5 m but can range for selected patients with intestinal failure. The small intestine may be
from 3 to 8.5 m (Teitelbaum et al 2013). Males have a longer small transplanted in isolation or along with the liver and/or other abdomi-
bowel than females, and height is positively associated with small nal organs such as the pancreas (multivisceral transplant). Postopera-
bowel length (Teitelbaum et al 2013). Short bowel syndrome results tively, patients are recommenced on parenteral nutrition, and enteral
from surgical resection, congenital deficiency or disease-associated loss feeding is started via a feeding jejunostomy once intestinal motility has
of absorption, and is characterized by the inability to maintain protein- returned. Protein is delivered as peptides and fats as medium-chain
energy, fluid, electrolyte or micronutrient balances when on a conven- triglycerides, which are absorbed directly into the mesenteric veins and
tionally accepted, normal diet (O’Keefe et al 2006). Left untreated, not via the lymphatics (which are divided when the graft is taken from
short bowel syndrome leads to dehydration, malnutrition and weight the donor). Parenteral nutrition can usually be discontinued 3–6 weeks
loss. Adults with the greatest risk of developing intestinal failure fall after transplantation but may continue to be used to supplement enteral
into three groups: those with an end-jejunostomy and <100 cm of feeding when stoma losses are large.
residual small bowel, those with a jejunocolic anastomosis and <50 cm Intestinal dysmotility is common after intestinal transplantation.
residual small bowel, and those with a jejunoileal anastomosis and There is no extrinsic nerve supply to the graft but intrinsic small bowel
<35 cm of residual small bowel (despite the presence of an ileocaecal motility usually recovers within 48–72 hours after transplantation
junction and colon) (Nightingale and Woodward 2006, Jeppesen (Gunning and Friend 1998). Adequate gastric emptying is often delayed
2013). for several weeks, despite pyloroplasty and the administration of drugs
After surgical resection, the remaining small bowel undergoes an to enhance gastric motility. Reinnervation of the allograft via its vascular
adaptive process that involves morphological and functional changes. pedicle is a slow process (Walther et al 2013). Intestinal motility is also
The small bowel dilates and villus height and crypt depth increase, affected by any inflammatory response caused by rejection. Denervation
expanding the absorptive surface area. Adaptation begins soon after and division of the lymphatic drainage of the intestinal allograft do not
intestinal resection and may continue for up to 2 years (Jeppesen and appear to seriously impair longer-term function. In animal models,
Mortensen 2002). However, there are differences between the ability lymphatic drainage is re-established within 21–28 days, which is con-
of the proximal and distal small bowel to adapt; the likelihood of sistent with observations in patients (Kocandrle et al 1966).
regaining intestinal autonomy is greatest in patients with a retained
segment of ileum and colon in continuity, as compared to patients
with a residual duodenojejunal segment and an end-jejunostomy
(Jeppesen 2013). | 1,563 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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A B Fig. 65.10 Specimens of the jejunum (A) and
ileum (B) from a cadaver where the superior
mesenteric artery was injected with red-coloured
gelatin before fixation. Subsequently, the
specimens were dehydrated and then cleared in
benzene, followed by methyl salicylate. The largest
vessels present are the jejunal and ileal branches
of the superior mesenteric artery and these are
succeeded by anastomotic arterial arcades, which
are relatively few in number (1–3) in the jejunum,
becoming more numerous (2–6) in the ileum. From
the arcades, straight arteries (arteriae recta) pass
towards the gut wall; frequently, successive
straight arteries are distributed to opposite sides
of the gut. Note the denser vascularity of the
jejunal wall. (Specimens prepared by MCE
Hutchinson; photographs by Kevin Fitzpatrick on
behalf of GKT School of Medicine, London.)
lymphoid tissue than the ileum. There are also differences between the Short bowel syndrome
mesenteric vessels in the jejunum and ileum (Conley et al 2010). The
jejunal mesentery, measured from the superior mesenteric artery to Available with the Gray’s Anatomy e-book
the mesenteric border of the bowel, is shorter than the ileal mesentery,
and the jejunal arteries are slightly larger than their ileal counterparts.
Small intestinal transplantation
The jejunum typically contains 1–3 tiers of vascular arcades, whereas
there are often 2–6 tiers in the ileum (Fig. 65.10). The arteriae recta in
Available with the Gray’s Anatomy e-book
the ileum are more numerous, shorter and narrower than in the
jejunum. The jejunal and ileal arteries, arcades and arteriae recta
are muscular arteries capable of influencing splanchnic blood flow,
VASCULAR SUPPLY AND LYMPHATIC DRAINAGE
which can vary between 10% and 35% of cardiac output (Rosenblum
et al 1997).
Solitary lymphoid follicles are scattered throughout the small intes- Arteries
tinal mucosa but are most numerous in the distal ileum. Aggregated Branches from the superior mesenteric artery supply the jejunum and
lymphoid follicles, Peyer’s patches, are circular or oval masses contain- ileum. The arteries divide as they approach the mesenteric border of
ing 5–260 follicles. They vary in size, shape and distribution, most the intestine (see Fig. 65.5), giving off numerous branches that extend
measuring 2–8 cm and visible macroscopically as dome-like elevations, between the muscular layers before forming a submucosal arterial
usually along the antimesenteric border of the intestine. They are rarely plexus that supplies the mucosa. Although there is a rich anastomotic
present in the duodenum; small, circular, few in number and impalpa- network of arteries within the intestinal mesentery, anastomoses
ble in the distal jejunum; and larger, more numerous and often palpa- between the terminal branches close to the intestinal wall are few. The
ble in the ileum (particularly in the terminal 25 cm; Van Kruiningen intramural and submucosal arterial networks consist of small-calibre
et al 2002). Villi are small or absent over the larger follicular masses. vessels only. Consequently, division or occlusion of several consecutive
Lymphoid aggregates are most prominent in early childhood and, when vasa recta may produce segmental ischaemia of the bowel, while divi-
enlarged in viral infections, may form the apex of an intussusception. sion of more proximal arterial branches in the small bowel mesentery
They become less prominent around puberty, and decrease further in may not cause ischaemia because of collateral flow through vascular
number during adult life (Cornes 1965). arcades.
Meckel’s diverticulum A congenital ileal diverticulum (of Meckel) Superior mesenteric artery
is found in 2–3% of individuals and represents the remnant of the The superior mesenteric artery originates from the abdominal aorta
proximal part of the vitellointestinal duct. It projects from the antime- 1 cm below the coeliac trunk, at the level of the lower border of the
senteric border of the terminal ileum and is commonly located between first lumbar vertebra in the transpyloric plane (Figs 65.13–65.14). The
50 and 100 cm from the ileocaecal junction. It is variable in length angle of its origin from the aorta is acute (mean value 45°, range
(usually 2–5 cm in adults) and often possesses a short ‘mesentery’ of 38–60° and greater in individuals with a greater body mass index;
adipose tissue containing a vitellointestinal artery (from the termina- Ozkurt et al 2007); this can make cannulation via the transfemoral
tion of the superior mesenteric artery) that extends from the ileal route somewhat difficult. The artery is usually surrounded by fat, lym-
mesentery to its base (Fig. 65.11). The lumen of the diverticulum phatics and neural tissue at its origin, which helps to increase the angle
usually has a calibre similar to that of the ileum. The tip is normally and distance between it and the aorta, thereby preventing compression
free but occasionally it may be connected to the anterior abdominal of the duodenum where it is crossed by the artery. The artery descends
wall near the umbilicus by a fibrous band. The mucosa is typically ileal, anterior to the uncinate process of the pancreas and the third part of
but small heterotopic areas of gastric body type epithelium, pancreatic, the duodenum, and posterior to the splenic vein and the body of the
colonic or other tissues may also occur in the wall of a diverticulum. pancreas. The left renal vein lies behind it and separates it from the
Unopposed acid secretion by heterotopic gastric body type epithelium aorta (Fig. 65.15B). Within the small bowel mesentery, the superior
may give rise to ulceration and bleeding in the adjacent normal ileal mesenteric artery crosses anterior to the inferior vena cava, right ureter
mucosa. Diverticular inflammation may mimic acute appendicitis; and right psoas major. Its calibre progressively decreases as successive
since Meckel’s diverticulum and the appendix are both derived from branches are given off to the jejunum and ileum, and its terminal
midgut structures, pain from either structure is referred to the perium- branch anastomoses with the termination of the ileocolic artery.
bilical region. Rarer complications of a Meckel’s diverticulum include The superior mesenteric artery usually gives off the inferior pancrea-
intestinal obstruction, intussusception, perforation, calculi and tumours ticoduodenal, middle colic, right colic and ileocolic branches from its
(Sagar et al 2006, Uppal et al 2011). right side, and jejunal and ileal branches from its left side. Its jejunal
and ileal branches form vascular arcades within the small bowel mesen-
Jejunostomy and ileostomy In clinical practice, a stoma is a tery. The last of these arcades forms an irregular and incomplete ‘mar-
surgically created opening from a hollow viscus to the skin, classified ginal artery’ of the small intestine. Straight arteries, the arteriae recta,
according to its location. An intestinal stoma may be either an end are given off from the most distal arcades and pass directly to the small
stoma, in which only the proximal end of the divided bowel is anasto- intestine.
mosed to the skin, or a loop stoma, in which both the proximal and Anatomical variations in the origin and branching pattern of the
distal ends of the bowel are exteriorized on the surface (Fig. 65.12). superior mesenteric artery are well described (Winston et al 2007,
The output of a jejunostomy is greater than that of an ileostomy and Horton and Fishman 2010) (see also p. 1144). It may be the source of
more likely to result in excessive fluid, electrolyte and nutrient losses. the common hepatic, gastroduodenal, accessory or replaced right | 1,564 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Middle colic artery Fig. 65.13 The superior mesenteric artery and its
branches. The outlines of representative ileal and
Right branch Middle branch Left branch Inferior pancreaticoduodenal artery
jejunal loops, appendix, caecum, ascending and
transverse colon are shown for reference. Only the
origin of jejunal and ileal branches is shown. For
details of arcades, see Figure 65.10.
Right colic artery
Jejunal branches
Ileocolic artery
Superior division
Inferior division
Anterior Ileal branches
caecal branch
Posterior
caecal branch
Appendicular artery
Terminal ileal branch
hepatic, accessory pancreatic, splenic or rarely the inferior mesenteric ileum, caecum and vermiform appendix. It ascends in the mesentery to
artery. Also rare is a superior mesenteric artery arising from a common the right of the superior mesenteric artery, passing anterior to the right
coeliacomesenteric trunk (Rountas et al 2013). ureter, inferior vena cava, third part of the duodenum and uncinate
The remnant of the vitellointestinal artery (the embryonic artery that process of the pancreas. It joins the splenic vein behind the neck of the
originally connected the intestinal circulation to the yolk sac) is usually pancreas in the transpyloric plane (lower border of L1 vertebra) to form
obliterated; when present, it forms the artery supplying a Meckel’s the portal vein.
diverticulum. It is occasionally represented in the mesentery by a fibrous The superior mesenteric vein receives jejunal, ileal, ileocolic, right
strand from the termination of the superior mesenteric artery to the colic, middle colic, right gastroepiploic and inferior pancreaticoduode-
ileum. nal veins. A major proximal jejunal branch usually runs transversely
behind the superior mesenteric artery to enter the right posterolateral
Jejunal branches There are usually 4–6 jejunal branches, which aspect of the superior mesenteric vein (Kim et al 2007). The right colic
arise from the left side of the upper portion of the superior mesenteric vein is highly variable. When present, it may drain into the superior
artery (see Figs 65.13–65.14). They are distributed to the jejunum via mesenteric vein directly, or may join the right gastroepiploic or inferior
1–3 tiers of arterial arcades, the most distal of which gives rise to straight pancreaticoduodenal vein to form a ‘gastrocolic trunk’, which then
arteries. The latter run almost parallel in the mesentery before being drains into the superior mesenteric vein (Yamaguchi et al 2002).
distributed alternately to either side of the small bowel, forming two Although the inferior mesenteric vein usually drains into the splenic
distinct ‘leaves’ of vessels within the mesentery separated by a relatively vein, it may join the superior mesenteric vein directly or its confluence
avascular plane (see Fig. 65.5A). with the splenic vein (Graf et al 1997).
This vascular arrangement allows a dilated segment of small bowel
Lymphatic drainage
to be bisected longitudinally and tubularized to double its length, a
potentially useful technique to achieve small bowel lengthening in The lymphatic system of the small intestine regulates tissue fluid homeo-
short bowel syndrome (Bianchi 1984). stasis, participates in immune surveillance, and transports dietary fat
Small twigs from the jejunal arteries supply regional mesenteric and fat-soluble vitamins from the gut lumen. It is organized into two
lymph nodes. networks. Firstly, lacteals from the villi drain into a plexus of lymphatics
in the submucosa and are joined by vessels from lymph spaces at the
Ileal branches Ileal branches are more numerous (around 8–12) bases of solitary lymphoid follicles; these lymphatic vessels have few, if
and slightly smaller in calibre than the jejunal branches. They arise from any, valves. Secondly, a coarse plexus of lymphatics also runs in the
the left and anterior aspects of the superior mesenteric artery. The length muscularis externa between the two muscle layers. The submucosal and
of the mesentery from the superior mesenteric artery to the mesenteric muscular networks share few connections but both communicate freely
border of the bowel is greater in the ileum, and the branches form with larger valved collecting lymphatics at the mesenteric border of the
between two and six arcades before giving rise to multiple straight arter- small intestine (Miller et al 2010). Mesenteric lymphatics pass between
ies that run directly towards the ileal wall (see Fig. 65.10B). These the layers of the mesentery and drain via a series of mesenteric lymph
branches run parallel in the mesentery and are distributed to both nodes concentrated around the regional mesenteric vessels. Individual
aspects of the ileum. They are shorter and thinner than their jejunal segments of small bowel have a relatively wide field of lymphatic drain-
counterparts, particularly in the distal ileum, and do not form such age, which makes radical surgical resection of draining lymph nodes
distinct parallel ‘leaves’ of vessels. The terminal ileal arcades are sup- difficult if the blood supply to the remaining unaffected small bowel is
plied by the ileal branch of the ileocolic artery and the last ileal branch to be preserved. Mesenteric nodes drain into superior mesenteric nodes
of the superior mesenteric artery (see Fig. 65.13). Few other vessels around the root of the superior mesenteric artery.
connect the ileocolic and superior mesenteric artery territories, which
makes surgical dissection of the ileocolic artery up to its origin relatively
simple. INNERVATION
Veins
The jejunum and ileum are innervated by parasympathetic and sympa-
Superior mesenteric vein thetic fibres via the superior mesenteric plexus (see Figs 59.2–59.4).
The superior mesenteric vein drains the small intestine, caecum, ascend- Preganglionic sympathetic axons originate from neurones in the
ing and transverse parts of the colon, and parts of the stomach and intermediolateral grey matter of the mid-thoracic spinal segments and
greater omentum (Fig. 65.16; see Fig. 59.8). It is formed in the mesen- travel in the greater and lesser splanchnic nerves to the coeliac and
tery of the small bowel by the union of tributaries from the terminal superior mesenteric ganglia, where they synapse. Postganglionic axons | 1,565 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Superior mesenteric artery
A
A
Coeliac trunk
Splenic vein Superior mesenteric artery
Superior mesenteric artery Jejunal branches
B
B
Ileocolic artery Ileal branches
Inferior vena cava Abdominal aorta Left renal vein
Fig. 65.15 A, An ultrasound image through the origin of the superior
mesenteric artery, sagittal plane. B, An axial CT scan in an adult
demonstrating the relationship of the superior mesenteric artery to the left
renal vein. (Courtesy of Professor Mark Stringer, Christchurch Hospital,
New Zealand.) (C, continued online)
accompany the superior mesenteric artery into the mesentery and are
distributed along branches of the artery. The sympathetic nerves are
vasoconstrictor to the vasculature and inhibitory to the musculature of
the jejunum and ileum. Sympathetic neurotransmitters also have an
immunomodulatory role by influencing mucosa-associated lymphoid
tissue (Straub et al 2006). Preganglionic parasympathetic axons travel
in the vagus nerves and are secretomotor to the mucosa and motor
to the smooth muscle of the jejunum and ileum. Visceral afferents from
the small bowel, conveying pain and other gut sensations, travel with
the splanchnic and vagus nerves.
C
Referred pain
Fig. 65.14 The superior mesenteric artery and its branches. A, A digital In common with other structures derived from the midgut, the visceral
subtraction angiogram. B, A surface-shaded, volume-rendered CT sensation of pain arising from the jejunum or ileum is poorly local-
angiogram. C, A sagittal reformat of a multislice CT angiogram. ized, and is usually referred to the periumbilical region.
(A, Courtesy of Dr Adam Mitchell, Charing Cross Hospital, London.
B, Courtesy of Dr Nasir Khan, Chelsea and Westminster Hospital,
SMALL INTESTINE PHYSIOLOGY
London. C, Courtesy of GE Worldwide Medical Systems.)
The principal functions of the small intestine are fluid and electrolyte
haemostasis, digestion and absorption of nutrients, immunoregulation,
and secretion of hormones. The absorptive capacity of the small | 1,566 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Falciform ligament Splenic vein Superior mesenteric artery
C
Inferior vena cava Abdominal aorta Left renal vein
Fig. 65.15 C, An axial ultrasound image showing the superior mesenteric
artery and the splenic vein. | 1,567 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Right hepatic Portal Retrohepatic inferior Left hepatic Splenic
vein vein vena cava vein vein
Circular folds
Fig. 65.17 The internal aspect of a representative sample of the proximal
jejunum, showing circular folds.
V
P
V
SM
P
IIeocolic vein Superior mesenteric vein Ileal vein Jejunal vein
Fig. 65.16 The superior mesenteric vein and its branches, CT venogram,
coronal plane. (Courtesy of Dr Nasir Khan, Chelsea and Westminster
Hospital, London.)
intestine is greatly enhanced by the plicae circulares, villi and microvilli,
Fig. 65.18 A low-power micrograph showing several circular folds
which increase its surface area by factors of approximately 2, 7 and 13,
(arrows) in the wall of the ileum. The folds are covered with villi (V)
respectively (Helander and Fändriks 2014), yielding a total estimated
projecting into the lumen, and the submucosa (SM) extends into the core
surface area of almost 30 m2.
of each fold. Circular (innermost) and longitudinal smooth muscle layers
form the underlying muscularis externa. Large masses of lymphoid tissue
(Peyer’s patches, P) lie in the mucosa. (Courtesy of Mr Peter Helliwell and
FLUIDS AND ELECTROLYTES
the late Dr Joseph Mathew, Department of Histopathology, Royal
Cornwall Hospitals Trust, UK.)
Available with the Gray’s Anatomy e-book
duodenum (see Fig. 59.9). The submucosa contains aggregates of lym-
NUTRIENTS
phoid tissue, most numerous in the ileum.
Circular folds
Available with the Gray’s Anatomy e-book
Except in the first part of the duodenum, large circular folds of mucosa
(known as plicae circulares or valvulae conniventes) project into the
MOTILITY
lumen of the small intestine, orientated either transversely or slightly
obliquely to its long axis (see Figs. 65.8, 65.17; Fig 65.18). Unlike
gastric folds, they do not disappear during physiological distension of
Available with the Gray’s Anatomy e-book
the intestine. Most extend round half or two-thirds of the luminal cir-
cumference, some are complete circles, some bifurcate and join adjacent
folds, while others are spiral and extend one or more times round the
MICROSTRUCTURE
lumen. Larger folds are up to 8 mm deep but most are smaller than
this, and larger folds often alternate with smaller ones. Folds begin to
The intestinal wall is composed of mucosa, submucosa, muscularis appear 2.5–5 cm beyond the pylorus and are relatively large and close
externa and serosa or adventitia (see Fig. 59.9). The mucosa is thick and together in the distal duodenum and proximal jejunum. Beyond this
very vascular in the proximal small intestine, but thinner and less vas- point, they diminish in size and disappear almost completely in the
cular distally. In places, it is ridged by the underlying submucosa to terminal ileum, which therefore has a relatively thin wall. The circular
form circular folds, plicae circulares, which protrude into the lumen; folds increase the absorptive surface area and enhance mechanical seg-
mucosal finger- or leaf-like intestinal villi cover the whole surface (Fig. mentation in the small intestine. They are visible at endoscopy (see Fig.
65.17). There are numerous simple, tubular intestinal glands or crypts 65.3), during small bowel contrast studies (see Fig. 65.6), and some-
between the bases of the villi, and additional submucosal glands in the times on plain radiographs. | 1,568 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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The secretion and absorption of electrolytes and fluid are two essential muscle of the small intestine exhibits cyclical myoelectrical activity, the
functions of the small intestinal epithelium. In healthy adults, the so-called migrating motor complex (MMC). The frequency of these
gastrointestinal tract is capable of secreting 8–10 litres of fluid per day slow waves is regulated by interstitial cells of Cajal and is about 11/
in addition to the 1.5–2 litres ingested each day. To reduce this volume minute in the jejunum, decreasing along the length of the small intes-
to the typical ileocaecal daily flow of approximately 2 litres per day, tine to 7–8/minute in the ileum (Husebye 1999). When slow waves are
the small intestinal epithelium has a large number of transport mole- amplified beyond a threshold by neural, endocrine or paracrine stimu-
cules and regulatory proteins. Net fluid movement across the gastro- lation, action potentials are generated, resulting in smooth muscle
intestinal epithelium is primarily the result of the active transport of contraction. This spreads circumferentially at first and then propagates
Na+, Cl−, and HCO− ions. The jejunum can only absorb sodium across along the entire circumference of the bowel in an aboral direction,
3
a small sodium gradient and therefore does not normally absorb salt causing a ring-like contraction of the circular smooth muscle that
and water, but secretes it into the lumen. Most fluid and electrolyte progresses down the small bowel (with about 10% of contractions
absorption occurs in the ileum, which is able to absorb across a larger reaching the ileum).
sodium gradient (Nightingale and Spiller 2001). The MMC consists of three phases: phase I is a period of quiescence,
phase II is composed of irregular contractions, and phase III is a short
The mucosal brush border has an abundance of enzymes and pumps burst of phasic contractions at the maximum frequency of the slow
on its surface. Examples include the sodium-dependent glucose trans- waves for that part of the intestine. The velocity of migration is 5–10 cm/
porter protein (SGLT1) and the fructose transporter protein (GLUT5). minute in the jejunum, decreasing gradually along the small bowel to
Most carbohydrates are broken down by enzymes to monosaccharides about 1 cm/minute in the ileum. The MMC requires an intact enteric
before being transported across the mucosa. A deficiency of lactase on nervous system and does not depend on extrinsic innervation. Conse-
the mucosal brush border is relatively common and results in lactose quently, MMCs are present in the transplanted (denervated) small
intolerance. Proteins are broken down into single amino acids and bowel. However, there is evidence that extrinsic innervation modulates
small peptides. The peptidase gradient across the microvillus brush the MMC. For example, sleep causes the almost complete disappearance
border increases along the length of the small bowel, suggesting that of phase II. Phase III activity normally recovers in the proximal small
amino acids are absorbed more distally than carbohydrates. Dietary fats bowel within a few hours of major abdominal surgery but the pressure
are emulsified by biliary secretions and then broken down by pancreatic wave amplitude is temporarily reduced. Somatostatin and opioids
lipase into free fatty acids and phospholipids, which form micelles. The decrease phase II activity.
lipid components are then absorbed within the distal small bowel and After a meal, the cyclical fasting activity is abolished for several hours
converted into chylomicrons in the enterocytes before being secreted and replaced by irregular contractions that consist of both segmental
into the lymphatic system. Minerals such as calcium, magnesium, phos- ‘stationary’ contractions and propulsive contractions (Barnert 2007).
phorus and iron, and the water- and fat-soluble vitamins, are predomi- Assessment of small bowel motility can complement detailed micro-
nantly absorbed in the duodenum and proximal jejunum (Farrell 2002, scopic examination of full-thickness biopsy specimens of the intestine
Malik and Westergaard 2002). Vitamin B is absorbed in the terminal when characterizing conditions associated with intestinal dysmotility,
12
ileum after binding to intrinsic factor released by gastric parietal cells. helping to distinguish intestinal neuropathy from visceral myopathy.
The motility of the small intestine differs, depending on whether the
individual is fasting or postprandial. In the fasting state, the smooth | 1,569 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
microstructure
1133
56
RETPAHC
the epithelium against pancreatic enzymes in the intestinal lumen. The
L
cell coat also contains a number of digestive enzymes as integral mem-
brane proteins. These include enzymes that degrade disaccharides and
oligopeptides prior to absorption.
IC
The luminal surface is an important barrier to diffusion. Nutrients
generally have to pass through enterocytes (transcellular absorption)
V before they reach the underlying lamina propria and its blood vessels
and lymphatics (lacteals). Classical epithelial junctional complexes
encircle the apical plasma membranes of adjacent enterocytes; their
tight junctions form an effective barrier to non-selective diffusion
between the gut lumen and the body as a whole. The lateral plasma
B membranes of enterocytes are highly folded, interdigitating with each
B other to form complex intercellular boundaries, anchored periodically
by desmosomes, and making contact at gap junctions. The lateral inter-
cellular space expands during active absorption and is an additional
conduit (supplementing transport across the basal cell surface) for the
passage of fluids, nutrients and other solutes to the vessels of the lamina
propria.
ME
Enterocytes have a lifespan after differentiation of about 5 days.
Their position on the villus wall reflects their stage in the life cycle; at
ME the tips of intestinal villi, they undergo programmed, apoptotic, cell
death and are shed from the epithelium. They are replaced at the base
of the villus by stem cell mitosis.
Goblet cells Goblet cells are most numerous in the distal small
Fig. 65.19 A low-power micrograph showing the wall of the duodenum,
intestine, increasing in number from the duodenum to their highest
with villi (V) projecting into the lumen (L); intestinal crypts (IC) of
density in the terminal ileum. They have elongated basal nuclei, an
Lieberkühn in the mucosa, seen mainly in transverse section; muscularis
apical region containing many membrane-bound mucinogen granules,
mucosae (arrows); submucosal seromucous (Brunner’s) glands (B); and
muscularis externa (ME). (Courtesy of Mr Peter Helliwell and the late and apical surfaces that bear a few short microvilli. Goblet cell mucins
Dr Joseph Mathew, Department of Histopathology, Royal Cornwall contribute to protection against microorganisms and toxins in the gut
Hospitals Trust, UK.) lumen, and also provide lubrication and mechanical protection from
the intestinal contents.
Microfold (M) cells Microfold cells are present where the epithe-
lium covers lymphoid aggregates in the intestinal wall. They are cuboi-
Intestinal villi
dal or flattened in shape and have long, widely spaced microfolds rather
than microvilli on their apical surfaces. They sample luminal antigens
Intestinal villi are highly vascular projections of the mucosal surface, by endocytosis, and transport antigen to lymphocytes lying within
just visible to the naked eye (see Fig. 65.18; Figs 65.19–65.21; Com- intercellular pockets formed by deep invaginations of the M-cell baso-
mentary 8.2). They cover the entire small intestinal mucosa, increase lateral plasma membranes. See Chapter 4 for details of antigen process-
the surface area of the lumen about seven-fold (Helander and Fändriks ing and presentation.
2014), and give it a velvety texture. Villi are large and numerous in the
duodenum and jejunum, and smaller and fewer in the ileum. In the Lymphocytes Intraepithelial lymphocytes are found in close asso-
first part of the duodenum, they appear as broad ridges, become tall ciation with M cells and also between the basolateral regions of entero-
and foliate in the distal duodenum and proximal jejunum, and then cytes and goblet cells. They are migratory cells derived from the
gradually shorten to a finger-like form in the distal jejunum and ileum. underlying lymphoid tissue and constitute an important means of
Villi vary in density from 10 to 40 per mm2 and from 0.5 to 1.0 mm in immune defence.
height (see Fig. 65.19). Infoldings of the mucosa dip down from the
base of the villi for a short distance into the lamina propria. These crypts intestinal glands or crypts
(of Lieberkühn) are most prominent in the proximal small intestine Intestinal glands or crypts (of Lieberkühn) are tubular pits that open
(see Fig. 65.20). into the lumen throughout the intestinal mucosa via small circular
apertures between the bases of the villi (see Fig. 65.20). Their thin walls
Mucosa are composed of columnar enterocytes supplemented by mucous
cells, Paneth cells, stem cells and neuroendocrine cells. They are sepa-
The mucosa consists of epithelium, lamina propria and muscularis rated by a basal lamina from a rich capillary plexus within the lamina
mucosae. propria.
Epithelium Enterocytes Enterocytes in the crypts secrete ions and alkaline fluid
A single-layered epithelium covers the intestinal villi (see Figs 65.20, to dilute chyme and aid absorption by structurally similar cells that
2.2C) and also lines the intestinal glands (crypts) that open between cover the villi.
the bases of villi. Two types of cell, enterocytes and goblet cells, cover
the surfaces of the villi, whereas microfold cells (M cells) are restricted Mucous cells The mucous cells in the crypts are similar to the goblet
to the dome epithelium that covers localized accumulations of lym- cells of the villi.
phoid tissues. These cell types are all in contact basally with a basal
lamina to which they adhere, and all are derived from a common stem Paneth cells Paneth cells are highly specialized epithelial cells of
cell in the intestinal crypts. the small intestine, involved in the coordination of many physiological
functions. They were first identified more than a century ago on the
Enterocytes Enterocytes are columnar absorptive cells, approxi- basis of their readily discernible secretory acidophilic granules that stain
mately 20 µm tall. They are the most numerous type of cell in the small strongly with eosin or phosphotungstic haematoxylin. Paneth cells are
intestinal lining, and are responsible for nutrient absorption. Their numerous in the deeper parts of the intestinal crypts. They synthesize
surfaces bear up to 3000 microvilli, which greatly increase the surface and secrete lysozyme, a highly specific antibacterial enzyme, other
area for absorption (Marsh and Swift 1969). Collectively, microvilli are defensive proteins (defensins) and tumour necrosis factor alpha (TNF-
visible by light microscopy as a brush border 1 µm thick; individual α), which help to protect the luminal surface. Recent studies have
microvilli can be resolved only by electron microscopy. Enterocyte shown that these antimicrobial molecules are key mediators of host–
nuclei are elongated vertically, mainly euchromatic and located just microbe interactions, including maintaining the homeostatic balance
below the centre of the cell. with colonizing microbiota and providing innate immune protection
The apical cell surface is resistant to protease attack because micro- from enteric pathogens (Clevers and Bevins 2013). In addition, Paneth
villi possess a specialized glycoprotein-rich surface coat (glycocalyx), cells secrete factors that help sustain and modulate epithelial stem and
which, with an overlying layer of mucus (Johansson et al 2011), protects progenitor cells in the crypts. | 1,570 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
SmAll inTESTinE
1134
8
nOiTCES
Direction of cell migration
Absorptive
enterocyte
Goblet cell
Central lymphatic
vessel (lacteal)
within the
lamina propria
Orifices of crypts of Lieberkühn
Fibroblasts
Epithelium Lymphoid follicle
Lamina
propria
Mucosa
Muscularis
mucosae
Submucosa
Circular muscle
Muscularis externa
Longitudinal muscle
Serosa
Fig. 65.20 The architecture of an intestinal villus. The various layers and cells are not drawn to scale.
Stem cells Stem cells occur in a zone just above the basal region of
the crypts. Lineage tracing has demonstrated that Lgr5hi crypt base
columnar stem cells generate all cell types of the small intestinal epi-
thelium (Barker et al 2007). These cells divide rapidly in the crypt
compartment directly above the Paneth cells. Their progeny (transit-
amplifying cells) move upwards from this compartment on to the
surfaces of the villi while differentiating into goblet cells, tuft cells,
neuroendocrine cells and enterocytes. An individual cell takes only
4–5 days to reach the villus tip and undergo apoptosis. Paneth cells
escape this upward flow and migrate downwards instead to settle at the
base of the crypt, where they can remain for one month or more
(Clevers and Bevins 2013). Stem cell daughter cells and young transit-
amplifying cells retain their plasticity and are able to revert back to stem
cells if the crypt is damaged and existing stem cells are lost.
Neuroendocrine cells Several types of neuroendocrine cell are
scattered among the walls of the intestinal crypts, and less commonly
over the villi. They secrete bioactive peptides, such as gastrin, chole-
cystokinin and secretin, basally into the surrounding lamina propria.
Crypt neuroendocrine cells are derived from stem cells, which also give
Fig. 65.21 The endoscopic appearance of the terminal villi (magnified). rise to enterocytes and other epithelial elements. | 1,571 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
1135
56
RETPAHC
Key references
Lamina propria the duodenojejunal junction. They are small, branched tubuloacinar
glands; each has several secretory acini lined by low columnar epithelial
The lamina propria is composed of connective tissue and provides
cells, which produce an alkaline (pH 9) mucoid secretion that effec-
mechanical support for the epithelium. It has a rich vascular plexus,
tively neutralizes acidic chyme from the stomach. Many neuroendo-
receives nutrients absorbed by the enterocytes, and forms the cores of
crine cells are present among the acinar cells.
the villi. It contains lymphoid tissue, fibroblasts and connective tissue
extracellular matrix fibres, smooth muscle cells, eosinophils, macro-
Muscularis externa
phages, mast cells, capillaries, lymphatic vessels and unmyelinated
nerve fibres. Plasma cells are numerous. Lymphocytes may be clustered
in solitary or aggregated follicles, some of which extend through the The muscularis externa consists of a thin, external, longitudinal layer
muscularis mucosae into the submucosa. and a thick, internal, circular layer of smooth muscle cells. It is thicker
in the proximal small intestine and is mainly responsible for the dif-
Villus core ferential appearance of proximal jejunum and distal ileum on CT
Each villus has a core of delicate connective tissue that contains a large, scanning.
blind-ending lymphatic vessel or lacteal (so called because of its content
of suspended chylomicrons, the droplets of apoprotein–lipid complex Interstitial cells of Cajal
elaborated by enterocytes from absorbed dietary fats). The core also
contains blood vessels, nerves and smooth muscle cells derived from
Interstitial cells of Cajal (ICC; p. 1043) are found throughout the entire
fine extensions of the muscularis mucosae. Each lacteal, usually single
length of the gastrointestinal tract, where they lie in close contact with
but occasionally double, starts in a closed dilated extremity near the tip
nerve terminals (Farrugia 2008). They originate from mesenchymal
of a villus, and extends through the core to the base of the villus, where
cells and may be considered to be specialized smooth muscle cells.
it joins a narrower lymphatic plexus in the deeper lamina propria. Its
However, whereas smooth muscle cells develop an extensive array of
wall is a single layer of endothelial cells. Smooth muscle cells surround
contractile elements, ICCs are fusiform cells with a large oval nucleus,
the lacteal throughout the villus and their contraction propels its con-
sparse cytoplasm, dendritic-like processes, few contractile elements, an
tents into the underlying lymphatic plexus. Capillaries within the core
abundance of endoplasmic reticulum and mitochondria, and charac-
are lined by fenestrated endothelium to facilitate the rapid intake of
teristic sets of channels in their membrane (Mostafa et al 2010). Distinct
nutrients diffusing from the covering absorptive epithelium.
networks are found in the myenteric plexus between the circular and
longitudinal muscle layers; ICCs contact each other and neighbouring
mucosa-associated lymphoid tissue
smooth muscle cells via gap junctions. Looser arrangements exist within
Mucosa-associated lymphoid tissue (MALT) consists of lymphoid fol-
the individual muscle layers and the submucosa of the gut. Isolated or
licles covered by follicle-associated intestinal epithelium, which includes
small groups of ICCs are also found in connective tissue septa and the
scattered M cells. MALT is found mainly in the lamina propria but
subserosal region. The cells are involved in the generation of pacemaker
sometimes expands into the submucosa; it is the source of B and T
signals, the propagation of electrical slow wave activity, neuromuscular
lymphocytes and other related cells involved in the immune defence of
transmission, and mechanosensation (Sanders et al 2014). Defective
the gut wall.
ICC function has been implicated in a wide range of intestinal motility
Like other masses of MALT (except lymph nodes), solitary and aggre-
disorders (Al-Shboul 2013).
gated lymphoid follicles are most prominent around the age of puberty,
after which they diminish in number and size, although many persist
Serosa
into old age. For further details of intestinal MALT and its function,
including Peyer’s patches, see Didierlaurent et al (2005).
Serosa is visceral peritoneum and consists of a subserous stratum of
Muscularis mucosae loose connective tissue covered by mesothelium. It covers the majority
The muscularis mucosae forms the base of the mucosa, and has external of the muscularis externa; the only exceptions are the part adjacent to
longitudinal and internal circular layers of smooth muscle cells. It mesenteric adipose tissue and the retroperitoneal portions of the duo-
follows the surface profiles of the circular folds and sends fine fascicles denum, both of which are covered mainly by a connective tissue adven-
of smooth muscle cells into the cores of the villi. titia rather than by serosa.
Submucosa Bonus e-book images
The submucosa is composed of loose connective tissue and contains
blood vessels, lymphatics and nerves. Its ridged elevations form the Fig. 65.7 A, Computed tomographic (CT) enterography. Coronal
cores of the circular folds. The geometry of its collagen and elastin slice showing small intestinal loops and superior mesenteric
fibres permits the considerable changes in transverse and longitudinal vessels. B, Magnetic resonance (MR) enterography. Coronal slice
dimensions that accompany peristalsis, whilst still providing adequate showing the small intestine and transverse colon.
support, elasticity and strength.
Fig. 65.11 A Meckel’s diverticulum containing ectopic mucosa at
Submucosal (Brunner’s) glands
its tip.
Submucosal glands are limited to the submucosa of the duodenum and
often referred to as ‘Brunner’s glands’ (see Fig. 65.19). Their ducts Fig. 65.12 A temporary loop ileostomy in an infant.
traverse the muscularis mucosae to enter the bases of the mucosal
crypts. They are largest and most numerous near the pylorus and form Fig. 65.15C An axial ultrasound image showing the superior
an almost complete layer in the proximal half of the descending duo- mesenteric artery and the splenic vein.
denum; thereafter, they gradually diminish in number and disappear at
KEY REFERENCES
Sanders KM, Ward SM, Koh SD 2014 Interstitial cells: regulators of smooth Teitelbaum EN, Vaziri K, Zettervall S et al 2013 Intraoperative small bowel
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cells of Cajal and their importance in smooth muscle function. Information on small bowel length in living adults, which varies with sex,
height and age. | 1,572 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Small intestine
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condition with many phenotypes. Expert Opinion Orphan Drugs Walther A, Coots A, Nathan J et al 2013 Physiology of the small intestine
1:515–25. after resection and transplant. Curr Opin Gastroenterol 29:153–8.
Jeppesen PB, Mortensen PB 2002 Enhancing bowel adaptation in short Winston CB, Lee NA, Jarnagin WR et al 2007 CT angiography for delineation
bowel syndrome. Curr Gastroenterol Rep 4:338–47. of celiac and superior mesenteric artery variants in patients undergoing
Johansson ME, Ambort D, Pelaseyed T et al 2011 Composition and func- hepatobiliary and pancreatic surgery. AJR Am J Roentgenol 188:
tional role of the mucus layers in the intestine. Cell Mol Life Sci W13–W19.
68:3635–41. Yamaguchi S, Kuroyanagi H, Milson JW et al 2002 Venous anatomy of the
Kamisawa T, Takuma K, Tabata T et al 2010 Clinical implications of accessory right colon: precise structure of the major veins and gastrocolic trunk
pancreatic duct. World J Gastroenterol 16:4499–503. in 58 cadavers. Dis Colon Rectum 45:1337–40. | 1,573 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
CHAPTER
66
Large intestine
absent from the caecum, vermiform appendix and rectum); and the
OVERVIEW
colonic wall is puckered into sacculations (haustrations), visible on
plain radiographs as incomplete septations arising from the bowel wall
The large intestine extends from the ileocaecal junction to the anus. It (see Fig. 66.2; Fig. 66.3). Its calibre is greatest near the caecum, gradu
begins as the caecum and vermiform appendix, which are usually ally diminishes towards the sigmoid colon, and then increases again in
located in the right iliac fossa. The ascending or right colon passes the rectum, where the lower third is dilated to form the rectal ampulla.
upwards in the right flank to the right hypochondrium, where it bends The mean internal diameter of the large intestine is 4.8 cm (Helander
to the left to form the hepatic flexure (right colic flexure) and become and Fändriks 2014).
the transverse colon. This loops across the abdomen with an anteroin During development, the large intestine is temporarily suspended
ferior convexity until it reaches the left hypochondrium, where it curves by a midline dorsal mesentery. However, after rotation of the gut in
inferiorly to form the splenic flexure (left colic flexure). From here, it utero, large portions of it come to lie adherent to the retroperitoneum,
descends in the left flank as the descending or left colon before continu while other segments remain suspended by a mesentery within the
ing as the sigmoid colon in the left iliac region. The sigmoid colon peritoneal cavity. The mesenteries of the colon consist of two layers of
descends into the true pelvis and becomes the rectum anterior to the visceral peritoneum enclosing adipose and connective tissues and sur
third sacral vertebra. The rectum transitions to the anal canal at the level rounding vessels, nerves and lymphatics that run forward from retro
of the pelvic floor (Figs 66.1–66.2). The large intestine thus runs from peritoneal structures. Where colonic mesenteries lie in contact with the
the ileocaecal (ileocolic) junction to the anal verge. It is formed from retroperitoneum, the potential space between the retroperitoneum and
the distal midgut, all of the hindgut, and the proctodeum (Ch. 72 and mesentery, referred to as the ‘subperitoneal space’, forms an avascular
Figs 72.4 and 72.7E). Knowledge of the development of the large intes plane during surgical dissection and allows the tracking of fluid, blood
tine not only helps to explain its anatomy, relations (including perito and disease (Oliphant et al 1996, Coffey 2013) (Ch. 62). The caecum
neal attachments) and neurovascular supply (Ch. 60), but is also may be firmly adherent to the retroperitoneum but is frequently sus
fundamental to understanding congenital large bowel disorders such as pended by a short mesentery, especially in infants. The ascending colon
anorectal malformations and malrotation of the gut. is usually adherent to the retroperitoneum, while the transverse colon
In the adult, the large intestine is approximately 1–1.5 m long in is suspended by a mesocolon and is freely mobile within the upper
vivo, although there is considerable individual variation. The large intes abdomen. The hepatic and splenic flexures may have a short mesentery.
tine differs from the small intestine in several ways: it has a greater The descending colon is adherent to the retroperitoneum, usually down
calibre; for much of its course it is more fixed in position; the outer to the level of the left iliac crest, and the sigmoid colon has a mesentery
longitudinal muscle layer of the colon is concentrated into three longi of variable length. The sigmoid mesentery shortens as it approaches the
tudinal bands, taeniae coli; small fatty projections, appendices epi pelvis and practically disappears at the level of the rectosigmoid junc
ploicae, are scattered over its free surface (although these tend to be tion. The rectum is a retroperitoneal structure.
First part of the duodenum
Spleen
Right lobe of the liver Tail of pancreas
Splenic flexure
Hepatic flexure
Transverse colon
Superior taenia
Third part of the duodenum
Left kidney
Right kidney
Descending colon
Ascending colon
Anterior taenia (libera)
Anterior taenia (libera)
Left iliac crest
Caecum
Sigmoid colon
Vermiform appendix
Rectum
1136 Fig. 66.1 An overview of the abdominal colon and its relations. | 1,574 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Splenic flexure
Hepatic flexure Appendices epiploicae
Transverse colon
Taenia libera
Fig. 66.2 The appearance of the colon on double contrast barium enema
examination, demonstrating the transverse colon and hepatic and splenic
flexures.
Taenia mesocolica
The posterior attachments of the small bowel mesentery and trans Taenia omentalis
verse mesocolon result in the peritoneal cavity being divisible into Fig. 66.3 Layers of the colonic wall.
named compartments (Ch. 62). The supracolic and infracolic compart
ments are separated by the attachment of the transverse mesocolon to
the posterior abdominal wall. Anteriorly, the transverse colon and trans
verse mesocolon are adherent to the posterior surface of the greater reflection on to the colonic wall. In the transverse colon, the taeniae
omentum. Lifting the greater omentum upwards exposes the infracolic are rotated as a consequence of the dependent position of this segment
compartment. This is divided by the root of the small bowel mesentery of colon and so anterior becomes inferior, posteromedial becomes
that descends obliquely from left to right; to the right lies the right posterior, and posterolateral becomes superior. The width of the taeniae
infracolic compartment, its apex the ileocaecal junction, and to the left, coli remains fairly constant throughout the colon but they broaden out
the left infracolic compartment, bordered laterally by the descending in the distal part of the sigmoid colon and gradually merge to form a
colon and continuous below with the pelvic cavity. complete longitudinal muscle layer around the rectum, which therefore
The microstructure of the large bowel corresponds to the general has no external sacculations.
pattern of the gut wall, having a mucous membrane consisting of epi
thelium, lamina propria and muscularis mucosa, surrounded by an
inner circular and outer longitudinal layer of muscle and a serosa (see INTERNAL APPEARANCE
Figs 66.3, 66.51). The mucosa also contains scattered neuroendocrine
cells derived from the amine precursor uptake and decarboxylation Colonic haustrations represent sites where the mucosa and submucosa
(APUD) cell lineage; these cells produce amines and/or peptides, which of the colonic wall is infolded; these folds partially span the bowel
act as hormones or neurotransmitters. Unlike the small intestine, the lumen but never form a complete, circumferential ring. The pattern of
mucosa of the large intestine lacks villi and the glands (crypts) contain haustrations and appearance of the colonic mucosa help the clinician
a high proportion of goblet (mucinsecreting) cells. In the appendix, appreciate the level reached during flexible endoscopic examinations of
the glands are sparse and numerous lymphoid follicles are found in the the colon (Silverstein and Tytgat 1991). In the caecum, the three longi
mucosa and submucosa. Although it is not a vital organ, the primary tudinal taeniae coli converge to form a characteristic ‘trefoil’ pattern on
function of the colon is transmission and elimination of intestinal the caecal wall (Fig. 66.4). The lower pole of the caecum is usually
contents, but it also has important absorptive and secretory roles. The devoid of haustrations, although a spiral mucosal pattern is often seen
anal sphincter is responsible for both continence and evacuation. The in the region of the orifice of the appendix (Fig. 66.5). The upper
large intestine has its own intrinsic (enteric) nerve supply, the activity caecum and ascending colon possess shallow but deep haustrations,
of which is modulated by extrinsic innervation. which may extend across onethird of the lumen (Fig. 66.6). In the
transverse colon, the haustrations often confer a triangular appearance
to the crosssection of the lumen when viewed along its axis at colon
EXTERNAL APPEARANCE oscopy (Fig. 66.7). The haustrations of the descending and sigmoid
colon tend to be thicker and shorter, producing a more circular cross
The haustrations of the colon are frequently absent in the caecum and section to the lumen (Figs 66.8–66.9). The wall of the colon is thinnest
often relatively sparse in the ascending and proximal transverse colon. in the region of the caecum and ascending colon, where it is most at
They become more pronounced beyond the middle of the transverse risk of perforation during therapeutic endoscopic procedures. The
colon. The sigmoid colon often has marked sacculation. Appendices overall luminal diameter is often smallest in the descending colon. The
epiploicae are small, fatfilled pouches of peritoneum that project from tortuosity of the sigmoid colon means that shorter lengths of colon are
the external surface of the colon and are supplied by blood vessels that visible during endoscopy than elsewhere in the colon. The haustrations
perforate the bowel wall. There are few, if any, appendices epiploicae of the rectum usually form consistent and recognizable transverse folds
on the serosal surface of the caecum, and only a limited number scat and the submucosal vessels tend to be more pronounced than in the
tered along the ascending colon. They are more common over the distal colon (Fig. 66.10). Distinct veins are usually visible during endoscopy,
colon and particularly numerous on the surface of the sigmoid colon, and are most marked above the anorectal junction.
where they can be large in the obese individual. The rectum has no
appendices epiploicae.
The three taeniae coli are located in fairly constant positions beneath RADIOGRAPHIC APPEARANCES
the serosal surface of the colon, except in the transverse colon. They are
found on the antimesenteric aspect of the colon directly opposite the Crosssectional imaging of the colon can be performed with computed
mesentery (taenia libera), posterolaterally (taenia omentalis) and pos tomography (CT) and magnetic resonance imaging (MRI). On axial
teromedially (taenia mesocolica) midway between the taenia libera and imaging, the colon may be filled with particulate faeces and air (Fig.
the mesentery (see Fig. 66.3). In the ascending and descending colon, 66.11). The wall in normal individuals is thin. The caecum and ascend
the posterolateral taenia is often obscured from view by the peritoneal ing colon often contain faecal residue and are easily identified in the | 1,575 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Ileocaecal
valve
Fig. 66.4 The endoscopic appearance Fig. 66.5 The endoscopic appearance of the orifice of Fig. 66.6 The endoscopic appearance of
of the caecum. The characteristic trefoil the appendix, seen as a slit-like depression near the the ascending colon.
appearance of the confluence of the three centre of this view of the caecal pole. The orifice varies
taeniae is usually obvious. from a small depression to an obvious luminal structure.
The ileocaecal junction is just visible in the top left
corner. (Courtesy of Dr Michael Schultz.)
Fig. 66.7 The Fig. 66.9 The
endoscopic appearance endoscopic appearance
of the transverse colon. of the sigmoid colon.
Note the characteristic Multiple large mucosal
triangular appearance folds are characteristic.
of the haustrations
when viewed
collectively (see also
Fig. 66.11C).
Fig. 66.8 The Fig. 66.10 The endoscopic
endoscopic appearance appearance of the rectum. Note
of the descending colon. the large transverse folds, with little
The lumen tends to look else in the way of mucosal folds,
rather more featureless characterizing the rectum. Prominent
than the more proximal submucosal vessels are often seen,
colon. particularly in the lower third.
retroperitoneum on the right. The transverse colon may contain faeces and superior rectal arteries, with a small contribution from branches of
or gas and lies in a variable position, suspended by its mesentery. The the internal iliac artery (the middle and inferior rectal arteries).
descending colon lies in the retroperitoneum on the left and often The arteries of the midgut and hindgut contribute to an anastomotic
contains little faecal residue. The volume data sets produced by modern vessel, the marginal artery of Drummond, which runs in the mesentery
multislice CT can now produce virtual colonoscopic mucosal images of along the inner margin of the colon and gives off short terminal
the distended and cleaned colon, and surfacerendered images of the branches to the bowel wall. These divide into vasa brevia, which pass
internal surface of the bowel (Fenlon 2002). directly through the muscularis externa of the colonic wall, and vasa
longa, which travel through the subserosa for a short distance before
running through the circular muscle, giving off branches to the appen
VASCULAR SUPPLY AND LYMPHATIC DRAINAGE
dices epiploicae (Fig. 66.13). The marginal artery is formed by the main
branches and arcades arising from the ileocolic, right colic, middle colic
Arteries
and left colic arteries. It is most apparent in the ascending, transverse
The arterial supply of the large intestine is derived from both the supe and descending colons (Fig. 66.14) and poorly developed in the
rior and the inferior mesenteric arteries (Fig. 66.12) (Jackson 1999). sigmoid colon. The marginal artery in the region of the splenic flexure
The caecum, appendix, ascending colon and proximal twothirds of the may be absent or of insufficient calibre to be of functional significance.
transverse colon (derived from the midgut) are supplied from ileocolic, Nevertheless, it may dilate considerably when one of the main visceral
right colic and middle colic branches of the superior mesenteric artery. arteries is compromised since it then provides a collateral arterial supply
The distal third of the transverse colon, descending and sigmoid colon, to the colon. The most susceptible part of the chain of anastomosing
rectum and upper anal canal (hindgut derivatives) are supplied pre vessels is at the junction of midgut and hindgut in the distal transverse
dominantly from the inferior mesenteric artery via the left colic, sigmoid colon near the splenic flexure. However, the arterial supply to this | 1,576 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Overview
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Fig. 66.11 The appearance of the colon on
multislice computed tomographic examination.
A, Axial CT. B, Coronal reformat showing
normal calibre and distribution of the abdominal
colon (ascending, transverse and descending).
C, Volume-rendering of the colonic wall using the
axial data set to produce virtual colonoscopic
views, showing the triangular lumen of the
transverse colon. D, Volume-rendering of the
air-filled colon using the axial data set to give an
image similar to a double contrast barium enema,
demonstrating haustrations. (A–B, By courtesy of
Dr Louise Moore, Chelsea and Westminster
Hospital. C–D, By courtesy of GE Worldwide
Medical Systems.)
A B
Ascending Transverse Descending Ascending Caecum Hepatic Small Descending Splenic
colon colon colon colon flexure bowel colon flexure
C D
Middle colic artery Fig. 66.12 The main branches of the superior and
inferior mesenteric arteries.
Middle branch
Right branch Left branch
Right colic artery
Ascending branch
Ileocolic trunk
Left colic artery
Superior division Descending branch
Inferior division
Inferior mesenteric artery
Anterior
caecal branch
Posterior
Sigmoid arteries
caecal branch
Appendicular artery
region may be augmented by an inner arterial arc (of Riolan), which an abdominal aortic aneurysm, when the descending colon remains
runs a meandering course in the colonic mesentery between the main viable because the marginal artery continues to receive an adequate
trunk of the middle colic artery and the ascending branch of the left blood supply from the left branch of the middle colic artery and the
colic artery (Fisher and Fry 1987, Gourley and Gering 2005). When sigmoid colon gains its supply from the middle and inferior rectal arter
present, this vessel is usually only prominent when there is occlusion ies via the superior rectal and sigmoid arteries. When colonic ischaemia
of the superior or inferior mesenteric artery. does occur, it is usually maximal in the region of the splenic flexure and
proximal descending colon because this segment is furthest from the
Colonic vascular occlusion collateral arterial supplies. Occlusion of the common iliac arteries may
The marginal artery of the colon may become massively dilated when also result in dilation of the marginal and inferior mesenteric arteries,
there is chronic stenosis or occlusion of the superior or inferior which become an important collateral supply to the lower limbs via
mesenteric artery. The latter may occur, for example, in association with dilated middle rectal arteries arising from the internal iliac artery. | 1,577 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Veins descending colon, sigmoid colon and rectum drain into nodes follow
ing the course of the inferior mesenteric artery (Fig. 66.16). In cases
The venous drainage of the large intestine is primarily into the portal
where the distal transverse colon or splenic flexure is predominantly
vein via the superior mesenteric and inferior mesenteric veins, although
supplied by vessels from the middle colic artery, the lymphatic drainage
some drainage from the rectum occurs via middle rectal veins into the
of this area may be predominantly to superior mesenteric nodes.
internal iliac veins, and inferior rectal veins into the internal pudendal
veins. Those parts of the colon derived from the midgut (caecum,
appendix, ascending colon and proximal twothirds of the transverse
colon) drain into colic branches of the superior mesenteric vein, while Right colic Right colic/middle Superior mesenteric Left colic Marginal
hindgut derivatives (distal third of the transverse colon, descending and artery colic trunk artery artery artery
sigmoid colon, rectum and upper anal canal) drain into the inferior
mesenteric vein (Fig. 66.15).
Lymphatic drainage
Lymph drainage from the large intestine follows the course of the arter
ies. Thus, lymphatic vessels of the caecum, ascending and proximal
transverse colon drain ultimately into lymph nodes related to the supe
rior mesenteric artery, while those of the distal transverse colon,
Feeding vessel
Mesentery
(e.g. marginal artery)
Terminal branch
Vasa brevia
Circular muscle
Vasa longa
Serosa
Taenia omentalis
Taenia mesocolica
Ascending Ileocolic Inferior Superior rectal Sigmoid Descending Ascending
Submucosal plexus
colic artery artery mesenteric artery artery branch branch
artery
Submucosa Appendicular vessel Fig. 66.14 The marginal artery running parallel to the colon and providing
an anastomosis between the branches of the superior mesenteric artery
Taenia libera Appendix epiploicae supplying the right side of the colon and the branches of the inferior
mesenteric artery supplying the left side of the colon (digital subtraction
Fig. 66.13 The typical pericolic arrangement of the arterial vasculature. arteriogram). (Courtesy of Dr J Jackson, Hammersmith Hospital, London.)
Middle colic vein Fig. 66.15 The main branches of the superior and
inferior mesenteric veins.
Right branch Left branch
Inferior mesenteric
vein
Ileocolic vein Ascending branch
Left colic vein
Superior branch
Descending branch
Inferior branch
Anterior caecal
branch
Posterior caecal
branch Sigmoid veins
Appendicular vein
Superior rectal vein | 1,578 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Midgut region of large intestine
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Middle colic nodes
Fig. 66.16 The lymph vessels and nodes draining
Superior mesenteric the large intestine.
Paracolic nodes nodes
Inferior mesenteric
Upper ileocolic
nodes
nodes
Ascending left
Right colic colic nodes
nodes
Left colic nodes
Paracolic nodes
Paracolic nodes
Lower ileocolic
nodes Descending left
colic nodes
Anterior caecal
nodes
Sigmoid nodes
Posterior caecal
nodes
Appendicular
nodes
Superior rectal Perirectal nodes
nodes
Colic nodes
Lymph nodes related to the colon form four groups: epicolic, paracolic,
intermediate colic and preterminal colic nodes. Epicolic nodes are
minute whitish nodules on the serosal surface of the colon, sometimes
within the appendices epiploicae. Paracolic nodes lie along the medial
borders of the ascending and descending colon and along the mesenteric Ileocaecal valve
borders of the transverse and sigmoid colon. Intermediate colic nodes
lie along the named colic vessels (the ileocolic, right colic, middle colic,
left colic, sigmoid and superior rectal arteries). Preterminal colic nodes
lie along the main trunks of the superior and inferior mesenteric arteries
and drain into preaortic nodes at the origin of these vessels.
Ascending mesocolic lymph nodes are significantly larger than
sigmoid mesocolic lymph nodes; this is relevant to lymph node retrieval
and examination after resection for colonic cancer (Ahmadi et al 2015).
Radical lymphadenectomy during resection of colorectal cancer
Terminal ileum
requires removal of the highest possible lymph nodes draining the
region of colon in which the tumour is located. In cases of cancer
of the rectum or sigmoid colon, this usually involves excision of the
preterminal colic nodes along the inferior mesenteric artery with liga
tion of the artery at its root or just below the origin of the left colic
Vermiform appendix
artery.
MIDGUT REGION OF LARGE INTESTINE
CAECUM
This blind pouch, measuring approximately 6 cm in length, lies below
Fig. 66.17 The caecum and ileocolic junction, double contrast barium
enema appearance.
the level of the ileocolic junction, anterior to the fascia covering the
right iliacus and psoas major, with the lateral cutaneous nerve of the
thigh interposed. The caecum usually lies adjacent to the anterior
tively large diameter of the caecum makes it liable to distension with
abdominal wall unless the greater omentum or loops of small bowel
increased intracolonic pressure and it is the region of the large intestine
are interposed. The caecum is often completely covered by peritoneum,
at greatest risk of perforation secondary to colonic distension (from
which is reflected posteriorly and inferiorly to the floor of the right iliac
obstruction or other pathology).
fossa. Peritoneal folds from the posterior caecal wall may create a variety
of peritoneal recesses around the caecum that have the potential to
Ileocolic junction
become sites of internal herniation; a superior and inferior ileocaecal
recess, a retrocaecal recess and a paracolic recess have been described
(Rivkind et al 1986). The retrocaecal recess frequently contains the The terminal ileum joins the posteromedial aspect of the large intestine
vermiform appendix. The three taeniae coli lie anteriorly, posteromedi at the junction of the caecum and colon, where it projects into the
ally and posterolaterally, and converge on the base of the appendix. lumen of the large intestine as the ileal papilla (Fig. 66.18A). It consists
During childhood, the lateral caecal wall outgrows the medial wall such of two labial folds; its precise shape and form varies from slitlike to an
that the orifice of the appendix, which is originally at the apex of the oval mucosal rosette, depending, in part, on the state of contraction or
caecum (Fig. 66.17), usually comes to lie slightly posteromedially. distension of the caecum. The upper labial fold is approximately hori
Fluid and electrolyte reabsorption by the large intestine begins in zontal and is at the junction between the ileum and colon; the lower
the caecum but occurs mostly in the ascending and transverse colon. lip is longer and more concave, and is at the junction between the ileum
The distensible ‘saclike’ morphology of the caecum allows storage of and caecum. At their bases, the labia fuse and continue as narrow
large volumes of semiliquid chyme from the small intestine. The rela mucosal ridges or frenula. | 1,579 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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A B
5mm
Fig. 66.18 A, The endoscopic appearance of the ileocolic junction (‘ileocaecal valve’), which appears as a bilabial structure on the left of this view of the
caecal pole. B, A photomicrograph showing a longitudinal section through the inferior labium of the ileal papilla (haematoxylin and eosin); the ileal
mucosa is visible superiorly. (A, Courtesy of Dr Michael Schultz. B, Courtesy of Drs. Matthew Pollard and Mark Stringer.)
The ileal papilla is formed by the mucosa, submucosa and external
muscle layers of the ileum, continuing through the wall of the colon Preileal
and combining with corresponding layers from the caecum inferiorly Taenia coli
and the colon superiorly (Fig. 66.18B). The internal surface of the
papilla is lined by small intestinal mucosa and its colonic surface is Postileal
covered by large bowel mucosa; these epithelial surfaces meet near the
tip of the papilla. A localized thickening of the muscle at the base of
the ileal papilla is consistent with physiological data that suggest the Caecum
presence of an intrinsic anatomical sphincter (Pollard et al 2012). In Ileum
addition, the bilabial configuration of the papilla may confer a valvular
function. The ileocolic junction performs several roles: it provides Retrocaecal
partial mechanical and functional separation of the luminal environ Promonteric
ments of the small and large intestine, which differ in their composi
tion, pH and bacterial content; it impedes reflux from the colon; and
it helps to regulate antegrade small bowel transit.
Caecal volvulus Paracolic/precaecal
Pelvic
If the caecum and ascending colon are attached to the posterior
abdominal wall by a narrow mesentery, the ileocolic region is at risk
of twisting about its mesenteric pedicle, creating a caecal volvulus. In Subcaecal
such cases, the caecum becomes markedly distended as a consequence
of the strangulating closed loop bowel obstruction that develops. Non
anatomical factors such as caecal distension may also contribute to the
pathogenesis of caecal volvulus (Madiba and Thomson 2002). Fig. 66.19 The major positions of the appendix encountered at surgery or
postmortem.
APPENDIX artery) (see Fig. 63.10). The luminal orifice is sometimes partially
covered by a mucosal fold forming an asymmetrical ‘valve’ (see Fig.
The vermiform (wormlike) appendix is a narrow, blindending tube, 66.5). The lumen may be widely patent in early childhood but is often
usually between 6 and 10 cm long in the adult. It joins the postero partially or wholly obliterated in the elderly. Agenesis or duplication of
medial wall of the caecum below the ileocolic junction. The appendix the appendix are exceptionally rare (Barlow et al 2013).
grows in length and diameter during early childhood, reaching almost
Microstructure
mature dimensions by about 3 years of age (Searle et al 2013). The
appendix usually lies in the right iliac fossa but its tip may occupy one
of several positions (Fig. 66.19) (Buschard and Kjaeldgaard 1973). In The layers of the wall of the appendix are similar to those of the large
clinical practice, the tip is most commonly retrocaecal or retrocolic intestine in general but with some notable differences. The serosa forms
(behind the caecum or lower ascending colon, respectively, anterior to a complete covering, except along the mesenteric attachment. The outer
iliacus and psoas major), or pelvic (when the appendix descends over longitudinal muscle is a complete layer of uniform thickness, except in
the pelvic brim, in close relation to the right uterine tube and ovary in a few small areas where the muscularis externa is deficient, allowing the
females). Other positions include subcaecal, and pre or postileal serosa to come into contact with the submucosa.
(anterior or posterior to the terminal ileum, respectively), especially The submucosa typically contains large lymphoid aggregates that
when a long appendicular mesentery allows greater mobility. The may extend into the mucosa and disrupt the integrity of the muscularis
surface marking for the base of the appendix has traditionally been mucosae (Fig. 66.20). The mucosa is covered by a columnar epithe
described by McBurney’s point (twothirds of the way along a line lium, which contains M cells where it overlies the mucosal lymphoid
between the umbilicus and right anterior superior iliac spine) but its tissue. Glands (crypts) (see Fig. 4.5) are similar to those of the colon
position is variable and affected by posture, caecal distension and other but are fewer in number and less densely packed. They penetrate deep
factors (Hale et al 2010). into the lamina propria. The submucosal lymphoid tissue frequently
The appendix has a continuous outer layer of longitudinal muscle exhibits germinal centres within its follicles (see Fig. 4.10), indicative
formed by the coalescence of the three taeniae coli. Its lumen is irregu of Bcell activation. Lymphoid follicles are absent at birth but accumu
larly narrowed by submucosal lymphoid tissue. The mesoappendix is a late during the first 10 years of life to become prominent. In adults, the
triangular mesentery running between the terminal ileum and appen lymphoid follicles gradually atrophy; in the elderly, the lumen of the
dix; it contains a variable amount of fat and frequently ends short of appendix may be partially obliterated by fibrous tissue.
the tip of the appendix. A small fold of peritoneum runs between the
terminal ileum and the anterior layer of the mesoappendix (the socalled Acute appendicitis
‘bloodless fold of Treves’), and another fold of peritoneum containing
the anterior caecal vessels extends from the terminal ileal mesentery
Available with the Gray’s Anatomy e-book to the anterior wall of the caecum (and contains the anterior caecal | 1,580 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Acute appendicitis may develop as a consequence of obstruction of the
lumen from inspissated material, a faecolith (appendicolith) or lym
phoid swelling. This can lead to suppuration, infarction and necrosis.
Appendicoliths are more common in children than adults but their
prevalence is variable, reflecting differences between populations, defi
nitions and methods of detection. In one radiographic study of normal
appendices removed incidentally at surgery or at autopsy, calcified fae
coliths were identified in 2.7% (Felson 1949). The increased size of the
appendicular orifice in early childhood and the decreased lumen in the
elderly may be reasons why acute appendicitis is less common in these
age groups. Although the appendix is well supplied by arterial anasto
moses at its base, the appendicular artery is an end artery; its close
proximity to the wall of the appendix makes it susceptible to thrombo
sis during acute appendicitis, which explains the high frequency of
gangrenous perforation seen in the disease.
Visceral afferent nerves are responsible for the initial symptoms of
acute appendicitis arising from distension and inflammation of the
organ: namely, colicky pain with or without vomiting. These afferent
nerves enter the spinal cord at around the level of the tenth thoracic
spinal segment. Abdominal pain from appendicitis is poorly localized
initially and referred to the central (periumbilical) region of the
abdomen, consistent with the midgut origin of the appendix. It is not
until parietal tissues adjacent to the appendix become involved in the
inflammatory process that somatic nociceptors are stimulated, resulting
in localization of pain to the right iliac fossa. Removal of the appendix
is not by itself associated with any discernible longterm sequelae but
this does not mean that it is an entirely vestigial organ. There is some
evidence that the appendix acts as a reservoir for normal gut flora,
enabling the large bowel flora to recover more rapidly after severe gas
troenteritis (Randal Bollinger et al 2007). | 1,581 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Ascending Right Transverse Third part of Inferior vena Small
colon kidney colon duodenum cava bowel
A
Fig. 66.20 A low-power micrograph of the appendix in transverse section,
showing part of its circumference and a faecal pellet lodged in its lumen.
Lymphoid tissue (basophilic staining) occupies much of the mucosa
between crypts, and part of the submucosa. The muscularis externa and
outermost serosal layer are seen at the right of the field.
Right kidney B
Transversus Second part Liver Right Hepatic Gallbladder Duodenum, third Transverse
abdominis of duodenum kidney flexure part colon
Iliohypogastric
Fig. 66.22 Axial CT images of the ascending colon obtained (A) at the
level of the mid ascending colon and (B) at the level of the hepatic
nerve
flexure, showing the relationship of the ascending colon and hepatic
flexure to the right lobe of the liver, the right kidney, the second part of
the duodenum, and the gallbladder. (Courtesy of Dr Louise Moore,
Chelsea and Westminster Hospital, London.)
Ilioinguinal
nerve
Gonadal vein
of the ascending colon are covered by peritoneum, which runs laterally
Iliac crest Gonadal artery into the right paracolic gutter and medially into the right infracolic
compartment. The ascending mesocolon is composed of two layers
Psoas major of mesothelium containing fat embedded within a connective tissue
Iliacus lattice, vessels and nerves; it is attached to the retroperitoneum of the
posterior abdominal wall via a layer of connective tissue (Coffey 2013,
Culligan et al 2014), known as Toldt’s fascia, which forms the plane of
Lateral femoral dissection when performing a right hemicolectomy.
cutaneous nerve
Hepatic flexure
The hepatic flexure, forming the junction between the ascending
Femoral nerve Genitofemoral nerve
and transverse colon, is variable in position, and has a less acute
angle than the splenic flexure. It overlies the anterior surface of the
lower pole of the right kidney, abutting the inferior surface of the right
lobe of the liver above (see Fig. 66.21; Fig. 66.22B), the second part of
the duodenum medially, and the fundus of the gallbladder anteromedi
Fig. 66.21 Posterior relations of the ascending colon. ally. The posterior aspect of the hepatic flexure is not covered by peri
toneum and is in direct contact with renal fascia. The greater omentum
often extends from its attachment to the transverse colon on to the
ASCENDING COLON hepatic flexure.
The ascending colon is 15–20 cm long and passes upwards from the
ileocolic junction to the right colic (hepatic) flexure, separated TRANSVERSE COLON
posteriorly by loose connective tissue from the iliac fascia, iliolumbar
ligament, quadratus lumborum, transversus abdominis, and the renal The transverse colon is intraperitoneal. It is highly variable both in
fascia anterior and inferolateral to the right kidney. The lateral femoral length (approximately 50 cm long on average) and the extent to which
cutaneous nerve, usually the fourth lumbar artery, and sometimes the it hangs down anterior to the small bowel between sites of attachment
ilioinguinal and iliohypogastric nerves lie posteriorly as they cross at the right (hepatic) and left (splenic) colic flexures. The greater curva
quadratus lumborum (Fig. 66.21). Both the lateral and anterior surfaces ture of the stomach and the gastrocolic omentum, which fuses with the | 1,582 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Occasionally, the ascending mesocolon is reflected forwards from
the posterior abdominal wall, conferring greater mobility on this
usually retroperitoneal part of the large bowel (Saunders et al 1995). | 1,583 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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transverse colon anteriorly and continues inferiorly as the greater ileal artery (Ouattara et al 2007) (see Fig. 66.12). Accessory appendicu
omentum, are superior. The transverse colon is suspended by the trans lar arteries are common; two or more arteries may supply the
verse mesocolon, which is attached from the lower pole of the right appendix.
kidney, across the second part of the duodenum and pancreas, to the
upper pole of the left kidney (see Fig. 63.2). The splenic flexure lies at Right colic artery
a higher level than the hepatic flexure, often abutting the spleen under The right colic artery is relatively small and variable in its anatomy
the left lower ribs. The disposition of the transverse colon and more (Batra et al 2013). It usually arises as a common trunk with the middle
posteriorly sited flexures results in the anterior taenia of the ascending colic artery, but may originate directly from the superior mesenteric
(and descending) colon lying inferiorly (see above). The transverse artery, or from the ileocolic artery (when it is referred to as an accessory
mesocolon affords considerable mobility to the transverse colon. Occa right colic artery) (Fig. 66.24). It passes to the right, across the right
sionally, the colon may be interposed between the liver and the dia psoas major and quadratus lumborum, crossing the right gonadal
phragm, when it may be mistaken for free intraperitoneal gas on vessels and ureter, just posterior to the peritoneal floor of the right
imaging; when associated with gastrointestinal symptoms it is referred infracolic compartment. Near the left side of the ascending colon, it
to as Chilaiditi’s syndrome (Murphy et al 2000). divides into a descending branch, which runs down to anastomose with
the superior branch of the ileocolic artery, and an ascending branch,
which passes up across the lower pole of the right kidney to the hepatic
VASCULAR SUPPLY AND LYMPHATIC DRAINAGE flexure, where it anastomoses with a branch of the middle colic artery.
OF THE MIDGUT Together, these anastomoses form the marginal artery at the hepatic
flexure.
Arteries
superior mesenteric artery Middle colic artery
The middle colic artery arises from the right side of the superior
The artery of the midgut is the superior mesenteric artery, which arises
mesenteric artery, either separately or in common with the right colic
from the anterior surface of the aorta at the level of the lower border
artery, just inferior to the neck of the pancreas, and passes anteriorly
of the body of the first lumbar vertebra. It runs steeply downwards,
and superiorly within the transverse mesocolon, just to the right of
posterior to the splenic vein and body of the pancreas, with the superior
the midline. As it approaches the colon, it usually divides into right and
mesenteric vein on its right, and directly anterior to the left renal vein,
left branches. The right branch anastomoses with the ascending branch
the uncinate process of the pancreas and the third part of the duode
of the right colic artery. The left branch supplies the terminal part of
num. It then enters the root of the mesentery of the small intestine and
the midgut and anastomoses with a branch of the left colic artery near
passes obliquely downwards and to the right, giving off several branches
the splenic flexure. The marginal artery thus formed lies a few centime
to the large intestine.
tres from the mesenteric edge of the transverse colon. Sometimes,
Ileocolic artery the middle colic artery divides into three or more branches within the
The ileocolic artery arises from the superior mesenteric artery near
the root of the mesentery of the small intestine, descending within the
mesentery to the right towards the caecum, and crossing anterior to the
right ureter, gonadal vessels and psoas major. It usually divides into Ascending branch Posterior caecal artery
superior and inferior branches, the superior branch running up along
Anterior caecal artery
the left side of the ascending colon to anastomose with the right colic
Inferior division of
artery (or right branch of the middle colic artery) (Veeresh et al 2012).
ileocolic artery
The inferior branch runs to the ileocolic junction and divides into
Colic branch
anterior and posterior caecal arteries, the appendicular artery, and an
ileal branch that passes to the left in the ileal mesentery to anastomose Ileal branch
with a terminal ileal branch of the superior mesenteric artery (Fig.
66.23). The latter therefore provides a collateral arterial supply to the Termination
caecum. The ileocolic artery provides the major arterial supply to the of superior
caecum; traction on the caecum in the direction of the anterior superior mesenteric artery
iliac spine will cause the artery to tent up the mesentery, allowing easy Mesenteric-terminal
identification of the vessel. ileal anastomosis
The appendicular artery usually arises directly from the ileocolic
Terminal ileal artery
artery and descends posterior to the terminal ileum to enter the meso
appendix a short distance from the base of the appendix (see Fig.
66.23). Here, it gives off a recurrent branch, which anastomoses at the Anastomosing
base of the appendix with a branch of the posterior caecal artery. The arcades
appendicular artery approaches the tip of the organ, at first near to, and
then in the edge of, the mesoappendix. The terminal part of the artery Recurrent branch
lies on the wall of the appendix and may become thrombosed in appen Appendicular artery
dicitis, resulting in distal gangrene or necrosis. Less commonly, the Fig. 66.23 The arteries of the caecum, vermiform appendix and
appendicular artery may arise from the posterior caecal artery or an ascending colon.
Middle colic artery Superior mesenteric artery Fig. 66.24 Anatomical variants of
the right colic artery.
Absent right colic artery: <5%
Separate right colic artery: 35%
Ileocolic artery
Accessory right colic artery: 10% | 1,584 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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A B C Fig. 66.25 Variants in the origin
of the middle colic artery; only
Middle colic artery
replaced arteries have been
Dorsal pancreatic artery Hepatic artery illustrated for simplicity.
Accessory arteries are more
common than completely
replaced arteries. A, The left
colic artery or inferior mesenteric
Middle colic artery artery. B, The dorsal pancreatic
artery. C, The hepatic artery. Each
Superior mesenteric
variant accounts for fewer than
artery
Middle colic artery 5% of cases.
Inferior mesenteric
artery Superior mesenteric Superior mesenteric
artery artery
Left colic artery
transverse mesocolon, in which case the most lateral branches form the
arterial anastomoses. An accessory, or rarely a replaced, middle colic
artery may arise directly from the aorta (Yoshida et al 1993), dorsal
pancreatic, hepatic, inferior mesenteric or left colic arteries (Fig. 66.25). Hilum of spleen
In addition, an accessory middle colic artery is occasionally found
arising from the superior mesenteric artery proximal to the origin of the
Tail of pancreas
actual middle colic artery (Turmezei and Cockburn 2009).
Veins Left renal vein
All the branches of the superior mesenteric artery are accompanied by
correspondingly named veins. These tributaries drain into the superior
mesenteric vein, which ascends to the right of the artery, crossing the
third part of the duodenum and uncinate process of the pancreas.
Behind the neck of the pancreas, at the level of the transpyloric plane
(the lower border of the body of the first lumbar vertebra), it joins the
splenic vein to form the portal vein, which ascends behind the first part
of the duodenum to reach the liver. The right colic vein is highly vari
able: it may drain either directly into the superior mesenteric vein, or
into the right gastroepiploic or inferior pancreaticoduodenal veins to
form a ‘gastrocolic trunk’ that drains into the superior mesenteric vein,
or it may be entirely absent (Yamaguchi et al 2002). Several tributaries
draining into one or more middle colic veins are highly variable in
extent and position. The middle colic veins drain either into the supe Left renal pelvis
rior mesenteric vein, just before its junction with the splenic vein, or
directly into the hepatic portal vein. The appendicular vein usually joins Left ureter
the caecal vein to become the ileocolic vein; infection from the appen
dix can therefore be carried directly to the liver via the portal vein. Inferior mesenteric
vein
Lymphatic drainage
Lymphatic vessels originate from both anterior and posterior aspects of
the colon. Lymph drainage from the midgut follows the course of the
superior mesenteric artery. Thus, lymph from the caecum and appendix
drains to nodes associated with the ileocolic artery, and from the distal
ascending colon and hepatic flexure to nodes along the right colic artery
(see Fig. 66.16). When the distal transverse colon and splenic flexure Fig. 66.26 Relations of the splenic flexure.
are predominantly supplied by the middle colic artery, lymph drainage
of this segment is also largely to superior mesenteric nodes. Lymphatic
vessels in the appendix are numerous and combine to form vessels that be peritoneal and omental adhesions between the two structures. It lies
ascend in the mesoappendix, occasionally interrupted by one or more more superiorly and posteriorly than the hepatic flexure.
nodes. They unite to form three or four larger vessels that anastomose
with lymphatic vessels draining the ascending colon into ileocolic
DESCENDING COLON
nodes.
The descending colon is 25–30 cm long and descends from the splenic
HINDGUT REGION OF LARGE INTESTINE flexure in the left hypochondrium to the level of the iliac crest, where
it curves medially anterior to iliacus to become the sigmoid colon. In
most adults it is retroperitoneal, covered anteriorly and on both sides
Splenic flexure
by peritoneum, but occasionally the descending colon is more mobile,
being suspended from the posterior abdominal wall by a short meso
The splenic flexure marks the junction between the transverse and colon (Saunders et al 1995). Its lateral peritoneal reflection in the left
descending colon, and lies in the left hypochondrium, anterior to the paracolic gutter is marked by a white line (of Toldt). The posterior
tail of the pancreas and the left kidney (Fig. 66.26). Its position with surface of the descending colon is separated by a layer of loose con
respect to the spleen is variable: it usually lies inferomedial to the lower nective tissue from the anterior renal fascia inferolateral to the left
pole, forming the colic impression, but it may lie anterior to the splenic kidney, transversus abdominis, quadratus lumborum, iliacus and the
hilum, or even a little above. The splenic flexure is often attached to the lateral margin of psoas major (Fig. 66.27). The subcostal vessels and
splenic capsule by a peritoneal ligament and inadvertent downward nerves, iliohypogastric, ilioinguinal, lateral femoral cutaneous, femoral
traction on the flexure during surgery may tear the splenic capsule. The and genitofemoral nerves, and, usually, the fourth lumbar artery also
phrenicocolic ligament attaches the flexure to the diaphragm below the lie posteriorly, and loops of jejunum are anterior. The descending
inferior pole of the spleen at about the level of the tenth rib. The splenic colon is smaller in calibre and more deeply placed than the ascending
flexure often adopts a very acute angle such that the end of the trans colon. Appendices epiploicae are more common in this part of the
verse colon overlaps the beginning of the descending colon; there may colon. | 1,585 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Left gonadal
Left ureter
vessels
Spleen
Left kidney
Psoas major
Genitofemoral
Subcostal
nerve
nerve
Internal iliac
Iliohypogastric artery
nerve
Quadratus Transversus
lumborum abdominis Upper roots
of the
sacral plexus
Ilioinguinal
Gonadal vein nerve Sigmoid colon
Gonadal artery Iliac crest
Psoas major
Iliacus Piriformis
Obturator
Genitofemoral nerve
nerve Lateral femoral External iliac artery and vein
cutaneous nerve
Fig. 66.28 Posterior relations of the sigmoid colon.
Femoral nerve
Diverticular disease
Available with the Gray’s Anatomy e-book
Fig. 66.27 Posterior relations of the descending colon.
MESOCOLON
The mesocolon extends along the entire length of the colon and is
SIGMOID COLON continuous with the small bowel mesentery proximally and the meso
rectum distally. The mesocolon consists of fat embedded within a con
nective tissue lattice and sandwiched between two layers of mesothelium;
The sigmoid colon runs from the lesser pelvis to the beginning of the
it also contains nerves, blood and lymphatic vessels, and lymph nodes.
rectum at the level of the third sacral vertebra. It is usually suspended
A layer of loose connective tissue, known as Toldt’s fascia, lies immedi
from the posterior abdominal and pelvic walls by a fanshaped sigmoid
ately posterior to the mesocolon, where it is adherent to the retroperi
mesocolon, but may be tethered by congenital adhesions to the parietal
toneum of the posterior abdominal wall (Culligan et al 2014). Complete
peritoneum over iliacus. Consequently, its length and position are
excision of the relevant segment of mesocolon by dissecting within or
highly variable. It usually lies within the pelvic cavity anterior to the
behind the plane of Toldt’s fascia has been shown to improve survival
rectum on the peritoneal surface of the bladder (and uterus in the
in colon cancer (Søndenaa et al 2014).
female). It is usually completely invested in peritoneum. The root of
the sigmoid mesocolon has an inverted Vshaped attachment; the right
limb of this inverted ‘V’ ascends from a point anterior to the third sacral RECTUM
vertebra to the bifurcation of the left common iliac vessels (crossed by
the left ureter) and descends from this point along the external iliac
The rectum is continuous with the sigmoid colon at the level of the
vessels.
third sacral vertebra and ends as it passes through the pelvic floor (the
Between the fixed junctions with the descending colon and rectum,
puborectalis part of levator ani), where it is continuous with the anal
the relations of the sigmoid colon are quite variable (Fig. 66.28). Later
canal. It descends within the sacrococcygeal concavity, at first running
ally are the left external iliac vessels, the obturator nerve, ovary or vas
posteriorly and then curving anteriorly. The junction between the ante
deferens, and the lateral pelvic wall; posteriorly lie the left external and
riorly directed distal rectum and the posteriorly directed anal canal is
internal iliac and gonadal vessels, ureter, piriformis and the sacral
the anorectal angle, which is maintained by puborectalis. This is 2–3 cm
plexus; anteroinferiorly lie the bladder in males, or the uterus and
anterior to and slightly below the tip of the coccyx, level with the apex
bladder in females; superiorly and to the right, the sigmoid colon is in
of the prostate in males. The rectum also deviates in three lateral curves:
contact with loops of the ileum. The gonadal vessels and ureter lie in a
upper, convex to the right; middle (the most prominent), convex to the
distinct fascial plane, which is the inferior extension of the retroperito
left; and lower, convex to the right. Both ends of the rectum are in the
neal perirenal fascia and is separate from the sigmoid mesocolon. This
median plane (Fig. 66.30).
plane can be recognized and separated during surgical resection of the
Although variable in absolute length, the rectum is often defined in
sigmoid mesocolon. The taeniae coli of the sigmoid colon are wider
clinical practice as extending approximately 15 cm above the external
than elsewhere in the colon, and coalesce at its distal end to form a
anal margin. Its upper diameter is similar to that of the sigmoid colon,
complete circumferential longitudinal muscle layer. Appendices epi
but more inferiorly it becomes dilated as the rectal ampulla. Unlike the
ploicae are particularly prominent in the sigmoid colon.
sigmoid colon, the rectum has no sacculations, appendices epiploicae
The position and shape of the sigmoid colon depend on its length
or taeniae coli. The taeniae merge a few centimetres above the recto
(which increases with age) and mobility; the length of the sigmoid
sigmoid junction, initially forming wide anterior and posterior muscu
mesocolon (usually longer in males); and the degree of distension of
lar bands that then fuse to form a continuous outer layer of longitudinal
the colon, rectum, bladder and uterus. The length of the sigmoid colon
muscle investing the entire length of the rectum. At the rectal ampulla,
and its mesentery vary between ethnic groups (Alatise et al 2013).
a few longitudinal muscle fibres pass forwards from the anterior rectal
wall to the perineal body and urethra (rectourethralis).
Sigmoid volvulus
The upper third of the rectum is covered by peritoneum on its ante
rior and lateral aspects, and the middle third by peritoneum on its
Available with the Gray’s Anatomy e-book anterior aspect only; the lower third is below the peritoneum. The | 1,586 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Rotation or volvulus of the sigmoid colon may occur around its
mesenteric attachment. Volvulus is more likely when the length of the
sigmoid colon and the length and width of its mesentery are greater
(Akinkuotu et al 2011). Volvulus does not occur when the sigmoid
colon and its mesocolon are short. The anatomical features predispos
ing to sigmoid volvulus are most commonly found in subSaharan
Africans and chronically institutionalized patients.
Acquired diverticula commonly occur in the sigmoid colon, particu
larly in Western populations. These diverticula frequently develop in
parallel rows between the mesenteric taenia coli and the two anti
mesenteric taeniae where the colonic wall is weaker; at this site, the
outer longitudinal muscle is deficient and the circular muscle is tra
versed by arteries supplying the submucosal vascular plexus (Slack
1962). However, the predilection of diverticula in the sigmoid colon
probably relates to causative factors rather than intrinsic differences in
the structure of this segment of the colon. In contrast, congenital diver
ticula may occur at any site in the colon (Fig. 66.29) and are often
found along the mesenteric border.
Fig. 66.29 A CT scan (coronal reformat) showing both right colonic and
sigmoid diverticulosis. (Courtesy of Dr Kamini Patel, Homerton Hospital,
London.) | 1,587 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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A B Sacrum
Sacral nerve root
Fibres of piriformis
Rectum
Posterior mesorectal
fascia
Obturator internus Mesorectal fat
Mesorectal vessel
Iliococcygeus part
of levator ani Mesorectal
(pararectal) lymph
Puborectalis part node
of levator ani
Ischio-anal fossa
External anal
sphincter
Fig. 66.30 A, A coronal T2-weighted MRI of the rectum. B, A line diagram illustrating the main features in A.
peritoneum is reflected anteriorly on to the urinary bladder in males to by mesorectal fascia, a distinct layer of connective tissue that is also
form the rectovesical pouch, or on to the posterior vaginal fornix in called the fascia propria of the rectum. This fascia limits the mesorec
females to form the rectouterine pouch (of Douglas). The level of this tum posteriorly and lies anterior to the presacral fascia (of Waldeyer),
reflection is higher in males; the rectovesical pouch is approximately separated by a socalled retrorectal ‘space’. The rectum and mesorectal
7.5 cm above the anorectal junction in males, while the rectouterine fascia are connected to the parietal fascia of the pelvis by two ‘lateral
pouch is approximately 5.5 cm above the anorectal junction in females. ligaments’ (see below) and one posterior ligament, the rectosacral fascia
In neonatal boys, the peritoneum extends on the anterior rectal wall as (Gaudio et al 2010). The latter is a thin layer of connective tissue that
far as the lower limit of the prostate. Superiorly, the peritoneum is passes obliquely downwards from the presacral fascia to fuse with the
firmly attached to the muscle layer of the sigmoid colon by fibrous mesorectal fascia posterior to the rectum 3–5 cm above the anorectal
connective tissue, but as it descends on to the rectum, it is more loosely junction (GarcíaArmengol et al 2008). The mesorectal fascia is sur
attached by fatty connective tissue, which allows considerable expan rounded by a thin and relatively avascular layer of loose areolar tissue,
sion of the upper half of the rectum. which separates it from the posterior and lateral walls of the true pelvis.
When the rectum is empty, the mucosa has several longitudinal folds Superiorly, the mesorectal fascia blends with the connective tissue
in its lower part, which become effaced during distension. The rectum bounding the sigmoid mesentery. Laterally, it extends around the
commonly has three permanent semilunar transverse or horizontal rectum and mesorectum, and becomes contiguous anteriorly with a
folds (although the number can vary), which are most marked in rectal denser condensation of fascia, conveniently described eponymously as
distension (see Fig. 66.10). Two types of horizontal fold have been Denonvilliers’ fascia. This fascia is sometimes confusingly known as
recognized. One consists of the mucosa, the circular muscle layer and rectovesical fascia in males but it extends caudal to the bladder and is
part of the longitudinal muscle, and is marked externally by an indenta particularly dense posterior to the prostate and seminal vesicles; it lies
tion. The other is devoid of longitudinal muscle and has no external immediately anterior to the mesorectal fascia, to which it may be fused
marking. The most superior fold at the beginning of the rectum may (Lindsey et al 2000). In females, Denonvilliers’ fascia combines with
be on either the left or the right and occasionally encircles the rectal the anterior mesorectal fascia to form the rectovaginal septum (Zhai
lumen. The middle fold is largest and most constant, and lies immedi et al 2009).
ately above the rectal ampulla, projecting from the anterior and right Mesorectal fascia is visible by CT, MRI and dissection (Bissett et al
wall just below the level of the anterior peritoneal reflection; the circular 2001). On MRI scans, the mesorectum appears as a fatfilled envelope
muscle is particularly prominent in this fold. The inferior fold is on the containing blood vessels and lymph nodes; small nerves are not visible
left and the most variable. but interlacing connective tissue strands can be seen. The mesorectal
fascia is recognizable on axial MRI images as a lowsignal layer sur
Relations Posterior to the rectum and mesorectum, separated by the rounding the mesorectum, corresponding to a distinct condensation of
presacral fascia, are the lower three sacral vertebrae, coccyx, median and fascia seen on histological sections (Brown et al 1999). Identification
lateral sacral vessels, and the lowest portion of the sacral sympathetic of this layer in patients with a malignant rectal tumour can help predict
chain. Laterally, the upper rectum is related to the sigmoid colon and/ the success of surgical resection. Branches of the inferior hypogastric
or small bowel, while below the peritoneal reflection lie levator ani, plexus and middle rectal vessels enter the mesorectum anterolaterally.
obturator internus, the obturator nerve and vessels, ureters, the inferior They are ensheathed by fascia and are sometimes collectively referred
hypogastric plexus, internal iliac vessels, piriformis and the sacral to as the ‘lateral rectal ligaments’. The number and calibre of the middle
plexus. Anteriorly, the rectum is related to the sigmoid colon and/or rectal vessels are highly variable; they may be very small or even absent
small bowel in both sexes, and the base of the bladder, seminal vesicles, (Sato and Sato 1991). The ‘lateral ligaments’ are not clearly seen on MRI
vas deferens, terminal parts of the ureters, and the prostate in males or CT scanning, and only appear as an identifiable structure with surgi
(see Figs 66.34, 76.17). In females, the cervix/body of the uterus and cal traction on the rectum. The fascia of the ‘ligaments’ is flimsy and
vagina are anterior, the latter separated from the rectum by a rectovagi probably plays little role in support of the rectum. Parietal fascia covers
nal septum. In postmenopausal females, and after childbirth, the con levator ani and the muscles of the side wall of the pelvis, and is continu
nective tissue of the rectovaginal septum may atrophy or become ous posteriorly with the presacral fascia (see Fig. 66.36).
thinned, reducing the support of the anterior rectal and posterior
vaginal walls. Rectal prolapse
Available with the Gray’s Anatomy e-book
MESORECTUM AND RECTAL FASCIAE
Rectocele
Although the rectum has no mesentery, its surrounding fat is enclosed
within a fascial envelope known as the mesorectum. This constitutes a Available with the Gray’s Anatomy e-book
distinct compartment that is intimately related to the rectum down to
the level of levator ani (Figs 66.31–66.36). It contains the superior
Rectal cancer
rectal artery and its branches, the superior rectal vein and its tributaries,
lymphatic vessels and nodes, and adipose connective tissue. The meso
Available with the Gray’s Anatomy e-book rectum is much bulkier posteriorly (see Figs 66.31, 66.32). It is enclosed | 1,588 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Large intestine
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In prolapse of the rectum involving all layers of the rectal wall, the mid tumour recurrence (Heald et al 1982). In total mesorectal excision, the
and upper rectum descend towards the pelvic floor on straining. Descent posterolateral plane of dissection is outside the mesorectal fascia but
occurs within the lumen of the rectum as a form of intussusception, anterior to the presacral fascia and its underlying venous plexus. Later
and may be a consequence of the large diameter of the rectal ampulla ally, the plane is interrupted only by small branches of the middle rectal
and relative fixation of the anal canal. The loose adipose tissue of the vessels; anteriorly, it merges with the rectovesical or rectovaginal fascia.
upper mesorectum and the ‘lateral ligaments’ offer only limited resist The inferior hypogastric plexus is closely related to the plane of dissec
ance against rectal descent. Chronic enlargement of the anorectal space tion laterally; these nerves must be preserved to retain bladder and
bound by levator ani commonly occurs in patients suffering from recur sexual function. Total mesorectal excision involves complete excision
rent rectal prolapse, but is probably a consequence rather than a cause of the rectum down to the level of the pelvic floor, where the puborec
of the prolapse. In females, the rectouterine pouch also descends with talis component of levator ani merges with the deep component of the
the anterior rectal wall. external anal sphincter. Superiorly, the inferior mesenteric artery is
When the rectovaginal septum is grossly effaced, especially in post ligated near its origin.
menopausal females, the pressure of defecation can cause bulging of In abdominoperineal excision of the rectum, it should be noted that
the rectal wall into the posterior vagina and, in extreme cases, through the mesorectum becomes extremely thin at the point where the rectum
the vaginal introitus. Weakness of the pelvic floor muscles contributes passes through levator ani. To achieve adequate surgical margins, the
to the prolapse by allowing descent of the perineum during straining. plane of dissection is through the ischioanal fossa and levator ani
An important concept in the surgical treatment of adenocarcinoma outside the puborectalis sling and into the mesorectal plane well above
of the rectum is the necessity of excising the rectum in continuity with the pelvic floor.
the mesorectum and its contained lymph nodes in order to avoid local | 1,589 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
LARgE inTEsTinE
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nOiTCEs
A B
Sacrum
Posterior mesorectum
Mesorectal vessel
Peritoneal
reflection
Posterior mesorectal
fascia
Bladder
Presacral vessel
Rectoprostatic
space
Presacral fat
Prostate
Rectum
Anterior
mesorectum
Anococcygeal raphe
Anterior
mesorectal Levator ani
fascia
Posterior external
Anterior external anal sphincter
anal sphincter
Anal canal
Fig. 66.31 A, A sagittal T2-weighted MRI of the rectum in a male. B, A line diagram illustrating the main features in A.
A B
Sacrum
Posterior mesorectum
Presacral vessel
Pelvic peritoneal
reflection
Posterior mesorectal
Uterus fascia
Mesorectal vessel
Bladder
Presacral space
Vagina
Rectovaginal
Rectum
septum
Levator ani
Anterior
mesorectum Anococcygeal
ligament
Anterior
mesorectal Puborectalis
fascia
External
anal sphincter
Anal canal
Fig. 66.32 A, A sagittal T2-weighted MRI of the rectum in a female. B, A line diagram illustrating the main features in A. | 1,590 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Hindgut region of large intestine
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RETPAHC
B
A
Base of broad Uterine cervix
ligament
Anterior mesorectal
Obturator internus fascia
Internal iliac vessel Rectum
Posterior mesorectum
Piriformis
Presacral fascia Mesorectal vessel
Posterior
Sacrum
mesorectal
fascia
Fig. 66.33 A, An axial T2-weighted MRI of the upper rectum in a female. B, A line diagram illustrating the main features in A.
A B Prostatic fascia
Anterior mesorectal
Prostate fascia
Prostatic venous
Obturator internus
plexus
Branches of inferior
hypogastric plexus Obturator fascia
Levator fascia Ischium
Levator ani Rectum
Ischio-anal fossa Mesorectal fascia
Gluteus maximus
Coccyx
Fig. 66.34 A, An axial T2-weighted MRI of the mid rectum below the peritoneal reflection in a male. B, A line diagram illustrating the main features in A.
A B
Bladder
Obturator internus
Vagina
Obturator fascia
Levator ani Anterior
(puborectalis) mesorectal fascia
Ischio-anal fossa Mesorectal fascia
Rectum above
Top of anorectal junction
anococcygeal
ligament
Tip of coccyx
Fig. 66.35 A, An axial T2-weighted MRI of the low rectum below the peritoneal reflection in a female. B, A line diagram illustrating the main features in A. | 1,591 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
LARgE inTEsTinE
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nOiTCEs
A B
Anterior mesorectal
Prostate fascia
Obturator internus Prostatic vessels
Obturator fascia Branches of inferior
hypogastric plexus
Mesorectum
Piriformis Piriformis
Mesorectal fascia Mesorectal vessels
Presacral
(piriformis) fascia
Sacrum
Fig. 66.36 A, A light microscope transverse section of the mid rectum (male, cadaveric specimen). B, A line diagram illustrating the main features in A.
Left colic
Inferior
artery
mesenteric
vein
Catheter Inferior mesenteric artery
Marginal
artery (of
Inferior Drummond) Ascending branch
mesenteric
Left colic artery
artery
Descending branch
Superior
rectal
Sigmoidal
artery
arteries
Sigmoid arteries
Fig. 66.37 A digital subtraction arteriogram showing the inferior Superior rectal artery
mesenteric artery and its branches.
VASCULAR SUPPLY AND LYMPHATIC DRAINAGE
OF THE HINDGUT
Arteries
inferior mesenteric artery
The artery of the hindgut is the inferior mesenteric artery (Figs 66.37–
66.39), which arises from the anterior or left anterolateral aspect of the
Fig. 66.38 The inferior mesenteric artery.
aorta behind the inferior border of the third part of the duodenum
3–4 cm above the aortic bifurcation, at the level of the third lumbar
vertebra. It runs obliquely down to the pelvic brim, beneath the peri thus formed supply the distal third of the transverse and the descending
toneal floor of the left infracolic compartment, initially anterior and colon. The left colic artery may originate from or in common with a
then to the left of the aorta. It gives off the left colic and sigmoid arter sigmoid artery (Murono et al 2015). Occasionally, an accessory, or
ies, and crosses the origin of the left common iliac artery medial to rarely a replaced, left colic artery may originate from the trunk of the
the ureter, with the inferior mesenteric vein lying between. Beyond the superior mesenteric artery or its middle colic or first jejunal branch
pelvic brim, it continues in the root of the sigmoid mesocolon as the (Fig. 66.40). When present, it runs laterally in the upper left colic
superior rectal artery. mesentery just inferior to the duodenojejunal flexure to supply the
upper descending colon, and forms part or all of the marginal artery in
Left colic artery the region of the distal transverse colon. The left colic artery may itself
The left colic artery usually arises from the inferior mesenteric artery give rise to an accessory left middle colic artery. Occasionally, the left
shortly after its origin, ascends within the left colic mesentery and colic artery gives rise to a branch shortly after its origin, which ascends
divides into an ascending and a descending branch (see Figs 66.38– in the mesentery and anastomoses directly with a similar descending
66.39). The ascending branch passes upwards across the left psoas branch of the left branch of the middle colic artery (the socalled arc of
major, gonadal vessels, ureter and left kidney, and is crossed by the Riolan; van Gulik and Schoots 2005).
inferior mesenteric vein; its terminal branches anastomose with those The dominant arterial supply of the splenic flexure is usually from
of the left branch of the middle colic artery within the transverse meso the left colic artery but may be from the left branch of the middle colic
colon. The descending branch passes laterally and downwards, and artery. The marginal artery in this region may be absent or small, but it
anastomoses with branches from the ascending branch and the highest may enlarge considerably if the inferior mesenteric artery is stenosed or
sigmoid artery to form part of the marginal artery. The arterial arcades occluded (see p. 1100). | 1,592 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Hindgut region of large intestine
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Posterior aspect of rectum
Superior rectal
artery Right branch
Inferior mesenteric artery
Main descending
branch
Left colic artery,
ascending branch
Left colic artery,
descending branch
Descending colon Middle rectal artery
Marginal artery
Levator ani
Terminal descending
branches
Inferior rectal
branch of internal Ascending branches
pudendal artery
Anal canal
Fig. 66.41 The arterial supply of the rectum.
Fig. 66.39 The vascular supply of the descending colon from the inferior
mesenteric artery via the ascending and descending branches of the left
Vascular ligation in left colonic resections
colic artery, coronal reformat CT. (Courtesy of Dr Louise Moore, Chelsea
and Westminster Hospital, London.) During resection of the distal descending and sigmoid colon, ligation
of the inferior mesenteric artery close to its origin preserves the bifurca
tion of the left colic artery and helps to maintain the arterial supply to
the proximal descending colon via the anastomosis between the left
branch of the middle colic artery and the ascending branch of the left
colic artery. Ligation of the left colic artery close to its bifurcation may
interfere with this supply and render the proximal descending colon
more likely to become ischaemic. Similarly, if the inferior mesenteric
vein is ligated, then the bifurcation of the left colic vein forms the route
of venous drainage from the proximal descending colon to the middle
colic vein.
Superior rectal artery
The principal arterial supply to the upper twothirds of the rectum is
Middle colic via the artery of the hindgut – specifically, its pelvic continuation, the
artery
superior rectal artery (Fig. 66.41). The inferior mesenteric artery crosses
the left common iliac vessels medial to the ureter and descends in
the medial limb of the sigmoid mesocolon, straddled by the inferior
Superior mesenteric artery hypogastric nerves on either side. As it crosses the pelvic brim, it
becomes the superior rectal artery. At the level of the third sacral verte
Left colic artery bra, where the rectum begins, the artery enters the upper mesorectum
in the midline and divides into two branches that descend, initially
posterolaterally, and then on each side of the rectum. Terminal branches
Inferior mesenteric artery
pierce the rectal wall and anastomose with branches of the middle and
inferior rectal arteries within the rectal submucosa.
Middle and inferior rectal arteries
The middle rectal arteries arise either directly from the anterior division
Sigmoid artery of the internal iliac artery or from the inferior vesical artery (vaginal
artery in females). When present, they enter the mesorectum antero
laterally in the ‘lateral ligaments’ and provide some additional supply
to the middle third of the rectum. The inferior rectal arteries are termi
nal branches of the internal pudendal arteries. They cross the ischio
anal fossa to enter the upper anal canal laterally and supply the internal
and external anal sphincters, the anal canal and perianal skin. Ascend
ing branches supply the distal third of the rectum, anastomosing with
Fig. 66.40 A replaced left colic artery arising from the middle colic branch
terminal branches of the superior rectal artery in the rectal submucosa.
of the superior mesenteric artery.
The rectum also receives a small arterial supply from the median sacral
artery via a branch that enters posteriorly at the level of the anorectal
Sigmoid arteries junction.
The inferior mesenteric artery gives rise to between two and five sigmoid
Veins
arteries, which descend obliquely in the sigmoid mesocolon anterior to
the left psoas major, ureter and gonadal vessels. They supply the distal inferior mesenteric vein
descending colon and sigmoid colon, and anastomose superiorly with The inferior mesenteric vein drains the rectum, sigmoid, descending
the left colic artery and inferiorly with the superior rectal artery. Unlike and distal transverse colon (see Fig. 66.15; Fig. 66.42). It begins as the
the arrangement in the small intestine, arterial arcades do not form continuation of the superior rectal vein from the rectal plexus, through
until the arteries are close to the wall of the colon, when small branches which it connects with the middle and inferior rectal veins. The inferior
arise that supply the sigmoid colon directly. A true marginal artery is mesenteric vein lies to the left of the inferior mesenteric artery in the
less obvious in the sigmoid colon. A significant interval often exists in retroperitoneum and ascends anterior to the left psoas major and left
the mesentery between the highest sigmoid artery and the descending ureter; it may cross the gonadal vessels or ascend medial to them. It lies
branch of the left colic artery; this forms a useful guide to the arterial just lateral or occasionally posterior to the duodenojejunal flexure,
territories during surgical dissection. where it can be located intraoperatively. The inferior mesenteric vein | 1,593 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
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Inferior mesenteric node
Inferior mesenteric
artery
Left colic vein
Preterminal node
Inferior mesenteric
vein
Intermediate nodes
Superior rectal Internal iliac nodes
Catheter in inferior
artery
mesenteric artery
Marginal vein
Pararectal nodes
Middle rectal
artery
Epirectal nodes
Inferior rectal artery
Fig. 66.42 The inferior mesenteric vein and its tributaries, digital
subtraction arteriogram. (Courtesy of Dr Adam Mitchell, Charing Cross Fig. 66.43 Lymph nodes of the rectum and upper anal canal (viewed from
Hospital, London.) behind).
receives the superior rectal vein, several sigmoid veins, and the left colic paracolic to intermediate nodes in the sigmoid mesocolon. Intramural
vein. It usually passes posterior to the lower border of the body of the lymph from the rectum and anal canal above the dentate line drains
pancreas and anterior to the left renal vein to drain into the splenic predominantly to pararectal nodes in the adipose tissue of the mesorec
vein, but it may drain into the confluence of the splenic and superior tum and then along lymphatics accompanying the superior rectal artery
mesenteric veins or directly into the superior mesenteric vein (Graf et al (Fig. 66.43). These intermediate nodes then drain to lymph nodes
1997). along the inferior mesenteric artery and, from there, to preaortic nodes.
Some lymphatics from the lower rectum travel with the middle and
Rectal venous plexus inferior rectal arteries to internal iliac nodes, and along the median
A rectal venous plexus surrounds the rectum and connects anteriorly sacral artery to presacral nodes. The clinical significance of such drain
with the vesical plexus in males or the uterovaginal plexus in females. age in relation to the spread of malignancy from the lower rectum is
It consists of internal veins beneath the mucosa of the rectum and upper debated (Bell et al 2009).
anal canal, and external veins lying outside the muscular wall. The
upper twothirds of the rectum and the internal part of the rectal venous
INNERVATION OF THE LARGE INTESTINE
plexus drain mainly to the superior rectal vein and, from there, to the
inferior mesenteric vein; the middle third of the rectum drains by one
or more middle rectal veins into the internal iliac vein; and the lower The innervation of the large intestine is complex, and includes the
third of the rectum and anal canal drains via inferior rectal veins into enteric nervous system (made up of motor neurones, intrinsic sensory
the internal pudendal veins. The rectal venous plexus is therefore a site neurones, and interneurones lying within the wall of the gut); the
of communication between the portal and systemic venous systems. autonomic nervous system (sympathetic and parasympathetic innerva
tion); and extrinsic sensory innervation (visceral afferents) (Brookes
Superior rectal vein et al 2009) (Ch. 59).
Venous tributaries from the rectal venous plexus ascend in the rectal The enteric nervous system consists of ganglionated nerve plexuses
submucosa and pierce the rectal wall to form the superior rectal vein. lying in the submucosa (Meissner’s plexus) and between the longitudi
This runs in the upper mesorectum and root of the sigmoid mesocolon nal and circular smooth muscle layers (Auerbach’s myenteric plexus).
to the left of the superior rectal artery, crossing the pelvic brim and left Collectively, these nerves are concerned with control of mucosal func
common iliac vessels to form the inferior mesenteric vein (see Figs tions (secretion, blood flow) and the propulsion of luminal contents
66.15, 66.44). by rhythmic and synchronized contractions. Motor neurones may be
inhibitory or excitatory. Intrinsic sensory neurones are activated by
Left colic vein mechanical stimuli such as stretch and muscle tension, and by chemical
The left colic vein is formed from several tributaries, including ascend stimuli released by neuroendocrine cells in the wall of the gut (see Fig.
ing and descending branches that correspond to similarly named arter 3.26). Sensory neurones project locally on to myenteric interneurones
ies. The left colic vein usually lies superior to its corresponding artery, and motor neurones, allowing the spread of reflex activity along the
and has a shorter course because the inferior mesenteric vein lies lateral gut. Interstitial cells of Cajal are present within the submucosal and
to the inferior mesenteric artery (see Fig. 66.42). Occasionally, there are myenteric nerve plexuses. In summary, they act as a link between
two left colic veins that both drain into the inferior mesenteric vein. smooth muscle cells and extrinsic neurones, and are responsible for the
intrinsic pacemaker activity of the gut; their activity is modulated by
Lymphatic drainage
autonomic nerves.
Small lymphoid aggregates measuring no more than a few millimetres The large intestine is richly innervated by sympathetic neurones that
are occasionally visible on the surface of the large bowel (epicolic and originate either directly from the sympathetic chain or indirectly via the
epirectal nodes). Lymph from the descending colon drains to paracolic aortic plexus; the former are mostly involved in the control of blood
nodes in the mesentery adjacent to the bowel and, from there, to inter flow (vasoconstriction), while the latter also influence the secretory
mediate nodes along the left colic artery (Jamieson and Dobson 1909). activity and motility of the gut. The cell bodies of preganglionic sym
Lymphatics from the sigmoid colon follow a similar pathway from pathetic fibres supplying the midgut are found in the intermediolateral | 1,594 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |
Anal canal
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columns of the fifth to the twelfth thoracic spinal segments and those create the anorectal angle. The anal canal lies 2–3 cm anterior and
of the hindgut in the intermediolateral columns of the first and second slightly inferior to the tip of the coccyx, opposite the apex of the prostate
lumbar spinal segments. Postganglionic sympathetic neurones from in males. At the anal verge, the squamous epithelium lining the lower
both sources release noradrenaline (norepinephrine), causing presyn anal canal becomes continuous with the skin of the perineum. The area
aptic inhibition within enteric circuits, slowing gut motility and driving of pigmentation of skin around the anal verge corresponds approxi
contraction of the ileocaecal and internal anal sphincters. Sympathetic mately to the extent of the external anal sphincter. Identification of the
supply to the midgut is conveyed to the coeliac and superior mesenteric anal verge may be difficult, particularly in males in whom the perineum
plexuses via the greater and lesser splanchnic nerves; postganglionic may ‘funnel’ upwards into the lower anal canal, but the characteristic
axons are distributed with branches of the superior mesenteric artery. puckering of the skin formed by the penetrating fibres of the conjoint
Sympathetic supply of the hindgut is conveyed via the lumbar splanch longitudinal muscle of the anal canal provides a useful landmark.
nic nerves that synapse in the abdominal aortic and inferior mesenteric The anal canal consists of an inner epithelial lining, a vascular
plexuses, and via sacral splanchnic nerves that synapse in the superior subepithelium, the internal and external anal sphincters, and fibro
and inferior hypogastric plexuses; postganglionic fibres are distributed muscular supporting tissue, as well as dense neuronal networks of
with branches of the inferior mesenteric artery and are inhibitory to autonomic and somatic origin. Functionally, it represents a zone of
colonic muscle. high pressure. It is between 2 and 5 cm long in adults; the anterior
The midgut receives its parasympathetic innervation from the vagus, wall is slightly shorter than the posterior. It is usually shorter in
via the coeliac and superior mesenteric plexuses, whereas the hindgut females. At rest, it forms an oval or triradiate slit in the anteroposte
receives its parasympathetic innervation from the pelvic splanchnic rior plane rather than a truly circular canal. The arrangement of the
nerves. The cell bodies of the pelvic splanchnic nerves are located in the external anal sphincter and its attachments to the perineal body and
second to fourth sacral spinal segments, the sacral parasympathetic coccyx create sites of maximum pressure in the anterior and posterior
nucleus. These parasympathetic fibres enter the inferior hypogastric midline of the canal.
plexus, where some synapse. From here, some pass directly to the Anteriorly, the middle third of the anal canal is attached by dense
rectum and other pelvic viscera while others ascend by one of two connective tissue to the perineal body, which separates it from the
routes: either within the hypogastric nerves to the superior hypogastric membranous urethra in males and from the lower vagina in females.
plexus to be distributed along branches of the inferior mesenteric artery, Laterally and posteriorly, the anal canal is surrounded by the loose
or by passing directly through the retroperitoneal tissues to reach the adipose tissue of the ischioanal fossae; this arrangement allows expan
splenic flexure and descending and sigmoid colon. Most preganglionic sion of the canal but offers a potential pathway for the spread of peri
parasympathetic neurones synapse in intramural plexuses in the gut anal sepsis. Posteriorly, the anal canal is attached to the coccyx via the
wall; from here, postganglionic neurones innervate the glands (secreto anococcygeal ligament, a midline fibroelastic structure that runs
motor) and muscle (motor) of the large intestine. Parasympathetic between the posterior aspect of the middle region of the external anal
stimulation is integral to colonic propulsion and defecation and to sphincter and the coccyx. The anococcygeal ligament is traditionally
relaxation of the internal anal sphincter. regarded as lying just inferior to the midline raphe of levator ani but
Visceral afferent impulses mediating sensations of distension and its relationship to the raphe is more complex (Kinugasa et al 2011).
spasm from the midgut travel with the vagus nerve while the hindgut The ischial spines may be palpated laterally by an examining finger
is innervated by afferent neurones with cell bodies in the lumbar in the upper anal canal. The pudendal nerves pass over the attachment
(mostly L2 and L3) and sacral dorsal root ganglia (mostly S1 and S2) of the sacrospinous ligament at this point and pudendal nerve motor
(Brookes et al 2009). These travel alongside autonomic nerves and are terminal latency may be measured digitally using a modified electrode
often erroneously referred to as ‘sympathetic afferents’ or ‘parasympa worn on the examining glove.
thetic afferents’. Visceral afferent innervation of intramural colonic
blood vessels probably conveys the sensation of colonic distension
(Song et al 2009), while visceral afferents in the rectum convey the LINING OF THE ANAL CANAL
sensation of rectal filling and are involved in reflex propulsive activity.
The upper part of the anal canal is lined by reddish columnar epithe
lium similar to that of the rectum; it contains secretory and absorptive
MOTOR FUNCTION OF THE LARGE INTESTINE cells with numerous tubular glands or crypts. Distally, the epithelium
becomes cuboidal and darker just above the level of the anal valves (Fig.
Healthy colorectal function includes absorption of water and sodium 66.47). The subepithelial tissues are mobile and relatively distensible,
from the bowel lumen, net antegrade propulsion of intestinal contents and contain submucosal arterial and venous plexuses.
at an adequate rate, and temporary faecal storage. Colonic motor activ In the midanal canal, there are 6–10 vertical mucosal folds, the anal
ity is greatest during the day and increases on waking and after meals. columns. These are better defined in children than in adults. The
It is characterized by sustained tonic contractions and brief phasic columns frequently contain a terminal branch of the superior rectal
contractions. Phasic contractions are subdivided according to whether artery and vein, supplemented to a variable degree by middle and infe
or not they propagate along the colon. Nonpropagating contractions rior rectal vessels (Thomson 1975). Dilated submucosal veins in the
are associated with segmental mixing of luminal contents, whereas upper anal canal form an internal haemorrhoidal venous plexus. Tiny
propagated sequences can be retrograde or antegrade. In the normal arteriovenous connections to these dilated submucosal veins give the
colon, antegrade activity occurs more frequently than retrograde blood within them a higher oxygen tension and therefore a redder
sequences, which are seen more in the proximal colon. Highamplitude colour than normal venous blood. The submucosal vessels are most
propagated contractions occur in adults 4–6 times per day, originate prominent in the leftlateral, rightposterior and rightanterior quad
anywhere in the colon (but mostly proximally), and migrate for a vari rants of the wall of the canal (approximately 3, 7 and 9 o’clock when
able distance distally (Narducci et al 1987, Bharucha 2012). They are viewed in the lithotomy position); here, the subepithelial tissues are
often associated with defecation or passing flatus. The sigmoid colon expanded into three ‘anal cushions’. Although variable in number and
exhibits cyclical bursts of motor activity, which may be important in position, the cushions help to seal the anal canal and contribute to the
modulating the delivery of faeces to the rectum. A highpressure zone maintenance of continence to flatus and fluid. The anal cushions are
with unique contractile properties in response to sigmoid and rectal important in the pathogenesis of haemorrhoids. The lower ends of the
distension or contraction has been demonstrated in the distal sigmoid columns form small crescentic folds, called anal valves, between which
(the socalled rectosigmoid sphincter; Shafik et al 2003). Rectal motor lie small recesses known as anal sinuses. The anal valves and sinuses
activity is characterized by motor complexes that can be triggered by together form the scalloped dentate (or pectinate) line, which is firmly
propagating contractions from the proximal colon and by the delivery anchored to submucosal connective tissue. Anal glands open into small
of stool or gas from the sigmoid colon. However, since these frequently depressions, anal crypts, in the anal valves. The glands are branched and
propagate retrogradely, it has been suggested that they help to keep the lined by stratified columnar epithelium. Cystic dilations in the glands
rectum empty, thereby preventing the untimely delivery of colonic may extend through the internal anal sphincter and even into the exter
contents. nal sphincter (SeowCheon and Ho 1994).
The epithelium below the dentate line is smooth and typically shows
an abrupt transition to parchmentcoloured, nonkeratinized, stratified
ANAL CANAL
squamous epithelium, which lacks sweat and sebaceous glands and hair
follicles but contains numerous somatic sensory nerve endings convey
The anal canal begins at the anorectal junction and ends at the anal ing sensations of touch, pain and temperature. It extends down to the
verge (Figs 66.44–66.46). It is directed posteriorly because the slinglike intersphincteric groove, a palpable depression at the lower border of
puborectalis component of levator ani pulls the rectum forwards to the internal sphincter. Below the intersphincteric groove, the anal canal | 1,595 | Gray's Anatomy | temp.pdf | https://archive.org/download/GraysAnatomy41E2015PDF/Grays%20Anatomy-41%20E%20%282015%29%20%5BPDF%5D.pdf | PDFPlumberTextLoader |