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The anterior abdominal wall comprises: skin, superficial fascia, abdom-
teriorly. The two lower intercostal and four lumbar arteries supply the
inal muscles (and their respective aponeuroses), transversalis fascia,
wall posterolaterally.
extraperitoneal fat, and parietal peritoneum.
Veins of the abdominal wall (Fig. 11.6)
Skin (Fig. 11.6) deep circumflex iliac artery (a branch of the external iliac artery) an-
The skin of the abdominal wall is innervated by the anterior rami of the The abdominal wall is a site of porto-systemic anastomosis. The lateral
lower six thoracic intercostal and iliohypogastric (L1) nerves. thoracic, lumbar and superficial epigastric tributaries of the systemic
circulation anastomose around the umbilicus with the para-umbilical
Fascia (Fig. 11.2) veins which accompany the ligamentum teres and drain into the portal
There is no deep fascia in the trunk. The superficial fascia is composed circulation.
of two layers:
• A superficial fatty layeraCamper’s fasciaawhich is continuous with Lymph drainage of the abdominal wall
the superficial fat over the rest of the body. See p. 35.
• A deep fibrous (membranous) layeraScarpa’s fasciaawhich fades
above and laterally but below blends with the fascia lata of the thigh The inguinal canal (Fig. 11.4)
just below the inguinal ligament and extends into: the penis as a tubular The canal is approximately 4 cm long and allows the passage of the
sheath; the wall of the scrotum and posteriorly; the perineum where it spermatic cord (round ligament in the female) through the lower ab-
fuses with the perineal body and posterior margin of the perineal mem- dominal wall. The canal passes obliquely from the deep inguinal ring
brane. It fuses laterally with the pubic arch. The fibrous fascial layer is in a medial direction to the superficial inguinal ring.
referred to as Colles’ fascia in the perineum. • The deep ring: is an opening in the transversalis fascia. It lies half-
way between the anterior superior iliac spine and the pubic tubercle.
Muscles of the anterior abdominal wall (Fig. 11.1) The inferior epigastric vessels pass medial to the deep ring.
These comprise: external oblique, internal oblique, transversus abdo- • The superficial ring: is not a ring but a triangular-shaped defect in
minis, rectus abdominis and pyramidalis (see Muscle index, p. 162). the external oblique aponeurosis lying above and medial to the pubic
As in the intercostal space, the neurovascular structures pass in the tubercle.
neurovascular plane between internal oblique and transversus muscle
layers. The walls of the inguinal canal (Fig. 11.4)
• Anterior: external oblique covers the length of the canal anteriorly.
The rectus sheath (Fig. 11.3) It is reinforced in its lateral third by internal oblique.
The rectus sheath encloses the rectus muscles. It contains also the super- • Superior: internal oblique arches posteriorly to form the roof of the
ior and inferior epigastric vessels and anterior rami of the lower six canal.
thoracic nerves. • Posterior: transversalis fascia forms the lateral part of the posterior
The sheath is made up from the aponeuroses of the muscles of the wall. The conjoint tendon (the combined common insertion of the inter-
anterior abdominal wall. The linea alba represents the fusion of the nal oblique and transversus into the pectineal line) forms the medial
aponeuroses in the midline. Throughout the major part of the length of part of the posterior wall.
the rectus the aponeuroses of external oblique and the anterior layer • Inferior: the inguinal ligament.
of internal oblique lie in front of the muscle and the posterior layer of
internal oblique and transversus behind. The composition of the sheath Contents of the inguinal canal
is, however, different above the costal margin and above the pubic • The spermatic cord (or round ligament in the female).
symphysis: • The ilioinguinal nerve (L1).
• Above the costal margin: only the external oblique aponeurosis is
present and forms the anterior sheath. The spermatic cord (Fig. 11.5)
• Above the pubic symphysis: about halfway between the umbilicus The spermatic cord is covered by three layers which arise from the
and pubic symphysis the layers passing behind the rectus muscle gradu- layers of the lower abdominal wall as the cord passes through the
ally fade out and from this point all aponeuroses pass anterior to the inguinal canal. These are the:
rectus muscle, leaving only the transversalis fascia. • External spermatic fascia: from the external oblique aponeurosis.
The lateral border of the rectusathe linea semilunarisacan usually • Cremasteric fascia and muscle: from the internal oblique
be identified in thin subjects. It crosses the costal margin in the trans- aponeurosis.
pyloric plane. • Internal spermatic fascia: from the transversalis fascia.
Three tendinous intersections firmly attach the anterior sheath wall The contents of the spermatic cord include the:
to the muscle itself. They are situated at the level of the xiphoid, the • Ductus (vas) deferens (or round ligament).
umbilicus and one between these two. These give the abdominal ‘six- • Testicular artery: a branch of the abdominal aorta.
pack’ appearance in muscular individuals. • Pampiniform plexus of veins: these coalesce to form the testicular
vein in the region of the deep ring.
Arteries of the abdominal wall (Fig. 11.6) • Lymphatics: from the testis and epididymis draining to the pre-
These include the superior and inferior epigastric arteries (branches of aortic nodes.
the internal thoracic and external iliac arteries, respectively) and the • Autonomic nerves.

30 Abdomen and pelvis