The common iliac arteries, each a continuation of the descending aorta, arise from the bifurcation (splitting into two) of the abdominal aorta at about the level of the fourth lumbar vertebra. The common iliac arteries bifurcate again into internal and external iliac arteries that supply oxygenated blood to the lower abdomen, pelvis, and legs.

On both the left and right sides, the common iliac artery is short, and each common iliac artery divides into an internal and an external iliac artery at about the level of the sacrum. Before bifurcating into internal and external iliac arteries, it gives rise to small branches that supply blood to the ureter and peritoneal structures. The external iliac arteries continue on to supply blood to the legs (lower limb) and the internal iliac arteries supply blood to pelvic and peritoneal structure.

The internal iliac arteries are prominent in the fetus...