The aorta enters the abdomen via the aortic hiatus in the diaphragm at the level of the 12th thoracic vertebra and ends at L4 in the transcristal plane (Fig. 42). It lies throughout this course against the vertebral bodies and is easily palpable in the midline.
Anteriorly, from above down, it is related to the pancreas (separating it from the stomach), the third part of the duodenum and coils of small intestine. It is crossed by the left renal vein. A large tumour of pancreas or stomach, a mass of enlarged para-aortic nodes, or a large ovarian cyst may transmit the pulsations of the aorta and be mistaken for an aneurysm.
The branches of the aorta are: 1 three anterior unpaired branches passing to the viscera: (a) the coeliac axis—giving off the
• hepatic artery
• splenic artery
• left gastric artery
(b) the superior mesenteric artery
(c) the inferior mesenteric artery
2 three lateral paired branches passing to viscera:
(a) the suprarenal artery
(b) the renal artery
(c) the testicular or ovarian artery
3 five lateral paired branches to the parietes:
(a) the inferior phrenic artery
(b) four lumbar branches
4 terminal branches:
(a) the common iliacs
(b) the median sacral artery.
The common iliac arteries pass, one on each side, downwards and outwards to bifurcate into the internal and external iliacs in front of the sacroil-iac joint, at the level of the sacral promontory. They give no other branches.
At the bifurcation, the common iliac artery is crossed superficially by the ureter — a convenient site to identify this latter structure in pelvic operations.
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.
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