The abdominal aorta begins at the level of the diaphragm, crossing it via the aortic hiatus, technically behind the diaphragm, at the vertebral level of T12.[1] It travels down the posterior wall of the abdomen, anterior to the vertebral column. It thus follows the curvature of the lumbar vertebrae, that is, convex anteriorly. The peak of this convexity is at the level of the third lumbar vertebra (L3).
It runs parallel to the inferior vena cava, which is located just to the right of the abdominal aorta, and becomes smaller in diameter as it gives off branches. This is thought to be due to the large size of its principal branches. At the 11th rib, the diameter is 122mm long and 55mm wide and this is because of the constant pressure.[2] The abdominal aorta is clinically divided into 2 segments:
The suprarenal abdominal or paravisceral segment, inferior to the diaphragm but superior to the renal arteries.
The Infrarenal segment, inferior to the renal arteries and superior to the iliac bifurcation.
Branches
The abdominal aorta supplies blood to much of the abdominal cavity. It begins at T12 and ends at L4 with its bifurcation into the common iliac arteries[1] and usually has the following branches:
Originates above the celiac trunk, below the diaphragm. Passes upward and medially to the suprarenal gland, and crosses crus of diaphragm of corresponding side. Supplies diaphragm and gives superior suprarenal arteries.
Arises just below the superior mesenteric artery. Right renal artery passes deep to the inferior vena cava to right kidney; here it divides into branches. Left renal artery passes deep to the left renal vein. Divides in hilum of kidney. Both arteries give inferior suprarenal arteries and ureteral branches.
Four on each side that supply the abdominal wall and spinal cord. The fifth pair is the lumbar branches of the iliolumbar arteries. They pass deep to the crura on side of vertebral bodies and pass deep to the psoas major and quadratus lumborum to enter the space between the internal oblique and transversus abdominis muscles. Each artery gives off a small dorsal branch, which gives a spinal branch to the vertebral canal and then continues to supply the muscles of the back.
Artery arising from the middle of the aorta at its lowest part. Represents the continuation of the primitive dorsal aorta; quite large in animals with tails but smaller in humans.
On the left side are the left crus of the diaphragm, the left celiac ganglion, the ascending part of the duodenum, and some coils of the small intestine.
A 3D illustration of the abdominal aorta at the iliac junction
Relationship with inferior vena cava
The abdominal aorta's venous counterpart, the inferior vena cava (IVC), travels parallel to it on its right side.
Above the level of the umbilicus, the aorta is somewhat posterior to the IVC, sending the right renal artery travelling behind it. The IVC likewise sends its opposite side counterpart, the left renal vein, crossing in front of the aorta.
Below the level of the umbilicus, the situation is generally reversed, with the aorta sending its right common iliac artery to cross its opposite side counterpart (the left common iliac vein) anteriorly.
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![The standard aortic measurement on abdominal ultrasonography, such as used for abdominal aortic aneurysms, is between the outer margins of the aortic wall.[3]](/en/File:Ultrasonographic_measurement_of_aortic_diameter_at_the_navel.svg)
