aorta

The aorta is the body's main highway for oxygen-rich blood — the great trunk pipe from which all the body's smaller arteries branch off. Every beat of the left ventricle sends a fresh surge of blood into it.

It is the largest artery in the body, carrying oxygenated blood out of the left ventricle through the aortic valve. It arches up out of the heart, curves over like a walking-stick handle (the aortic arch), then runs down through the chest and abdomen, giving off branches to the head, arms, organs, and legs along the way. The very first branches it gives off are the coronary arteries that feed the heart itself.

The aorta's wall is thick and elastic, stretching with each surge of blood and recoiling between beats to keep flow smooth — a cushioning effect that softens the pulse. With age or disease its wall can weaken and balloon out (an aortic aneurysm) or tear between its layers (an aortic dissection), both of which can be life-threatening.