Page 168 - Clinical Anatomy

ECA2 7/18/06 6:43 PM Page 153

The posterior abdominal wall 153

The external iliac artery runs along the brim of the pelvis on the medial
side of psoas major. The artery passes below the inguinal ligament to form
the femoral artery, giving off, immediately before its termination, the
inferior epigastric artery, which demarcates the medial edge of the internal
inguinal ring (Fig. 45) and also the deep circumflex iliac artery.
The internal iliac artery passes backwards and downwards into the
pelvis, sandwiched between the ureter anteriorly and the internal iliac vein
posteriorly. At the upper border of the greater sciatic notch it divides into
an anterior and posterior division, which give off numerous branches to
supply the pelvic organs, perineum, buttock and sacral canal.

Inferior vena cava (Fig. 110)
The inferior vena cava commences at L5 by the junction of the common iliac
veins behind the right common iliac artery (unlike the usual arrangement of
a vein being superficial to its corresponding artery). It lies to the right of the
aorta as it ascends until separated from it by the right crus of the diaphragm
when the aorta pierces this muscle. The inferior vena cava itself passes
through the diaphragm at T8 (Fig. 11), traverses the pericardium and drains
into the right atrium.
As the inferior vena cava ascends, it is related anteriorly to coils of small
intestine, the third part of the duodenum, the head of the pancreas with the
common bile duct, and the first part of duodenum. It then passes behind the
foramen of Winslow, in front of which lies the portal vein, separating it
from the common bile duct and hepatic artery. Finally, the inferior vena
cava lies in a deep groove in the liver before piercing the diaphragm. Within
the liver it receives the right and left hepatic veins. Occasionally these veins
fuse into a single trunk which opens directly into the inferior vena cava;
on other occasions the central hepatic vein (which usually enters the left
hepatic near its termination) drains directly into the inferior vena cava
(Fig. 74). These variations are now of importance because of the possibility
of carrying out resection of one or other lobe of the liver.

Lumbar sympathetic chain

The lumbar part of the sympathetic trunk commences deep to the medial
arcuate ligament of the diaphragm as a continuation of the thoracic sympa-
thetic chain (see Fig. 276). On each side it lies against the bodies of the
lumbar vertebrae overlapped, on the right side, by the inferior vena cava
and on the left by the aorta.
The lumbar arteries lie deep to the chain but the lumbar veins may cross
superficial to it and are of importance because they may be damaged in per-
forming a sympathectomy.
Below, the lumbar trunk passes deep to the iliac vessels to continue as
the sacral trunk in front of the sacrum. Inferiorly, the chains converge and
unite in front of the coccyx as the small ganglion impar.
Usually the lumbar trunk carries four ganglia, although sometimes
these are condensed to three. All four send grey rami communicantes to the