The abdominal aorta (Latin: aorta abdominalis) is the abdominal part of the descending aorta and the largest artery in the abdomen. It is the continuation of the thoracic aorta after it enters the abdomen via the aortic hiatus of the diaphragm. The abdominal aorta terminates by dividing into the right and left common iliac arteries.
The abdominal aorta begins at the aortic hiatus of the diaphragm at the level of the lower part of the vertebra T12. The abdominal aorta descends along the posterior wall of the abdomen, traveling down the midline along the anterior surface of the bodies of the vertebrae L1 to L4. The abdominal aorta ends on the left of the midline at the lower level of the vertebra L4, where it divides into the right and left common iliac arteries.
Along its course through the posterior abdominal region, the anterior surface of the abdominal aorta is covered by prevertebral plexus of nerves and ganglia. It is also related to several other structures in the abdomen:
- located anterior to the abdominal aorta is the pancreas, as well as the splenic vein, left renal vein, and the inferior part of the duodenum;
- posteriorly, it is crossed by several left lumbar veins as they pass to the inferior vena cava;
- situated on its right side are the cisterna chyli, thoracic duct, azygos vein, right crus of the diaphragm, and the inferior vena cava;
- located on the left side of the abdominal aorta is the left crus of the diaphragm.
The abdominal aorta gives off many essential branches, mainly to supply the abdominal region with oxygenated blood. These branches can be categorized into three groups:
- posterior branches - supplying the diaphragm or body wall;
- visceral branches - supplying internal organs;
- terminal branches - providing mainly the pelvis and lower limb.
The posterior branches of the abdominal aorta supply the diaphragm or the body wall and include the following arteries:
- inferior phrenic arteries,
- lumbar arteries, and
- median sacral artery.
There are paired and unpaired visceral branches arising from the abdominal aorta.
Three unpaired visceral branches originate from the anterior surface of the aorta. They are also known as the anterior branches of the abdominal aorta and include the following arteries:
- coeliac trunk,
- superior mesenteric artery, and
- inferior mesenteric artery.
The paired visceral branches arising on each side of the abdominal aorta include the following:
- middle suprarenal arteries,
- renal arteries,
- testicular (in males) or ovarian arteries (in females).
The terminal branches of the abdominal aorta are the right and left common iliac arteries arising from its bifurcation, which usually occurs at the level of the L4 vertebra.