(3.58)

Now we’ll move on to look at the blood vessels of the abdominal region - first the arteries, then the veins. We’ll start by looking at the part of the descending aorta that lies below the diaphragm, the abdominal aorta.

Here’s the posterior abdominal wall with the arteries in place and the veins removed. Here’s the abdominal aorta. It enters the abdomen by passing though the aortic opening in the diaphragm at the level of the twelfth thoracic vertebra. The aorta runs down on the front of the lumbar vertebral bodies, just to the left of the mid-line. It ends by dividing at the level of L4, into the right and left common iliac arteries. The point where it divides is called the aortic bifurcation.

In looking at the branches of the abdominal aorta we’ll begin with the three which arise in the midline and supply the gastro-intestinal organs. Then we’ll look at the branches that arise in pairs. The three midline branches are the celiac trunk, the superior mesenteric, and the inferior mesenteric.

The celiac trunk arises immediately below the margin of the aortic opening at the level of T12. It divides into three branches: the common hepatic, the left gastric, and the splenic. Between them these supply the liver, stomach, duodenum, pancreas and spleen.

The superior mesenteric artery arises at the level of L1. Its branches supply the small intestine and much of the large intestine. The inferior mesenteric artery arises at the level of L3. Its branches supply the distal part of the large intestine.

Of the branches of the aorta that arise in pairs, much the largest are the right and left renal arteries, which supply the kidneys. They arise just below the level of the superior mesenteric artery.

Arising at about L2 are, in the female, the ovarian, and in the male the testicular arteries, which run downward and laterally over the psoas muscle.

Four pairs of lumbar arteries arise from the back of the aorta. Here are the lower two. They pass behind psoas major, where they branch to supply the back, the spine, and the abdominal wall.

Lastly, here’s the median sacral artery, which arises from the back of the aorta just above the bifurcation, and passes down into the pelvis.

Next we’ll look at the common iliac arteries and at their branches. On each side the common iliac artery divides into the internal and external ilac arteries. The common iliac artery runs close to the medial border of psoas major. It divides here, at the pelvic brim. Here’s the external iliac artery, here’s the internal.

We’ll look at the internal iliac in the next section. The external iliac artery is the main artery to the lower extremity. It runs along the pelvic brim just medial to psoas major, and passes beneath the inguinal ligament. Below the inguinal ligament the artery goes by a different name: the femoral artery.

Just before passing beneath the ligament, the external iliac gives off two branches, the deep circumflex iliac laterally, and the inferior epigastric medially.