Aorta

Aorta, principal artery of the body that carries oxygenated blood to most other arteries in the body. In humans the aorta rises from the left ventricle (lower chamber) of the heart, arches back and downward through the thorax, passes through the diaphragm into the abdomen, and divides into the right and left iliac arteries at about the level of the fourth lumbar vertebra. The aorta gives rise to the coronary arteries, which supply the heart muscle with blood, and to the innominate, subclavian, and carotid arteries, which supply the head and arms. The descending part of the aorta gives rise, in the thorax, to the intercostal arteries that branch in the body wall. In the abdomen it gives off the coeliac artery, which divides into the gastric, hepatic, and splenic arteries, which supply the stomach, liver, and spleen, respectively; the mesenteric arteries to the intestines; the renal arteries to the kidneys; and small branches to the body wall and to reproductive organs. The aorta is subject to a condition known as atherosclerosis, in which fat deposits attach to the aortic walls. If left untreated, this condition may lead to hypertension or to an aneurysm (a swelling of the vessel wall), which can be fatal.