Abdominal aorta, inferior vena cava and their branches

The aorta enters the abdomen at T12 between the crura of the diaphragm and ends at L4 by dividing into the common iliac arteries, which in turn divide into the external and internal iliacs. The external gives no branches apart from just above its termination into the common femoral artery – the inferior epigastric and deep circumflex iliac. The internal iliac artery gives off numerous visceral and body wall branches to the pelvic organs, pelvic wall, perineum and buttock region. The aorta gives off visceral branches anteriorly (coeliac, superior and inferior epigastrics) and laterally (suprarenal, renal and gonadal – testicular and ovarian – as well as inferior phrenic, four lumbar and the middle sacral artery). The inferior vena cava commences by the junction of the common iliac veins in front of L5. It lies immediately to the right of the aorta but is considerably longer because it ascends to the right crus of the diaphragm to pierce the central tendon of the diaphragm at T8, having deeply grooved the posterior aspect of the liver at its bare area. The tributaries of the inferior vena cava differ from the branches of the aorta in two respects. First, those corresponding to the anterior visceral branches of the aorta form the portal vein, which passes into the liver at the porta hepatis. Venous blood then returns to the inferior vena cava via the right, middle, left and accessory hepatic veins. Second, the suprarenal and gonadal veins on the left side, unlike those on the right, which drain directly into the inferior vena cava, empty into the left renal vein, which then crosses the front of the aorta to enter the inferior vena cava.