Oxygenated blood begins its course down the chest through thethoracic aorta, a major blood vessel with branches that serve the chest muscles and lungs. This becomes theabdominal aorta.

The abdominal aorta’s largest branch, thesuperior mesenteric artery, supplies blood to most of the small intestine and the first half of the large intestine. Theinferior mesenteric arteryhandles the second half of the large intestine’s blood supply.

In the pelvis, the abdominal aorta forks into two branches calledcommon iliac arteries. These travel down each leg, where they branch intointernaland external iliac arteries. These branch further to supply the legs. The largest of these branches are thefemoral arteries.

Branching from the internal iliac artery, theinternal pudendal arteryis the main vessel that supplies oxygenated blood to the penis and makes erections possible. Thetesticular arteries, also known as the internal spermatic arteries, supply blood to the testes. They branch from the abdominal aorta.

Veins are the blood vessels that return oxygen-depleted blood back to the heart for reuse. They typically follow the same path as arteries. Similar to the arteries in the pelvis, veins branch within the legs. As blood returns to the heart these branches — theexternal iliac veins— feed into theinferior vena cava, the large vessel that runs parallel to the abdominal aorta.

Nervesbranch from the spinal column. There are three types of nerves:

  • Autonomic nerves: These control involuntary or partially voluntary actions such as heartbeat.
  • Motor nerves: These signal muscles to move.
  • Sensory nerves: These relay information from the skin and muscles, such as heat and pain.

In the pelvis, the spinal column ends in thesacrum, five fused vertebral bones that form the back of the pelvis. Behind it is thesacral plexus, a collection of nerves that serve the pelvic area, genitals, buttocks, and parts of the legs and feet.

Thesciatic nerveis the largest nerve, and originates from the sacral plexus. This large nerve fiber begins in the lower back at the spinal column, runs through the buttocks (beneath the gluteus maximus muscle), and extends down the back of the thigh. There is one sciatic nerve in each leg, and each is about one inch wide in the pelvis.