aorta, primary artery of the circulatory system in mammals, delivering oxygenated blood to all other arteries except those of the lungs. The human aorta, c.1 in. (2.54 cm) in diameter, originates at the left ventricle of the heart. After supplying the coronary arteries that nourish the heart itself, the aorta extends slightly toward the neck to feed branches serving the head and arms. It then arches down toward the waist, directing blood into the arterial system of the chest. Entering the abdomen through the aortic hiatus, an opening in the diaphragm, the aorta branches off to supply the stomach, kidneys, intestines, gonads, and other organs through extensive arterial networks. It finally divides into the two iliac arteries carrying blood to the legs. The elasticity of the aorta wall permits it to pulse in rhythm with the heartbeat, thus helping to propel blood through the body.

Congenital disorder involving narrowing of a short section of the aorta's arch over the heart. It causes a characteristic murmur, abnormally high blood pressure in the arms, and reduced blood flow to the abdomen, pelvis, and legs. It increases the workload of the left ventricle, which usually becomes enlarged. Surgical reconstruction or replacement (depending on the person's age) of the narrowed area is most effective in the young.

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Artery that carries blood from the heart to all the organs and structures of the body. Where the left ventricle opens into the aorta, a valve prevents backflow of blood into the heart. The aorta ascends from the heart, arches over it to the left, then descends into the trunk. Arteries branch off along its length until it divides at hip level into arteries that go to the legs.

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