Bock, Walter J. Department of Biological Sciences, Columbia University, New York, New York.
Last reviewed:November 2019
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The main vessel of the systemic arterial circulation arising from the heart. The aorta (see illustration) is the main artery leaving the heart in all vertebrates and some invertebrates. In mammals, reptiles, and birds, which possess two heart ventricles (muscular chambers that pump blood out of the heart), the aorta arises from the left ventricle. Divided into three parts for convenience only, the aorta carries blood from the heart to various organs and other structures of the body. The first portion is termed the ascending aorta and passes upward under the pulmonary artery; the coronary arteries arise at the base of the ascending aorta behind the aortic valves. The second part, or aortic arch, curves over the hilum of the left lung, giving off the innominate, left carotid, and left subclavian arteries, which supply the neck, head, and forelimbs. The third portion, or descending aorta, continues downward in the thorax on the left side of the vertebral column to the diaphragm, giving off small arteries to the bronchi, esophagus, and other adjacent tissues. Below the diaphragm, the vessel known as the abdominal aorta descends to the level of the fourth lumbar vertebra, where it bifurcates into the two common iliac arteries supplying the hindlimbs. See also: Blood; Blood vessel; Cardiovascular system; Circulation; Heart (invertebrate); Heart (vertebrate)
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