Aorta (Gr.air vessel), the largest artery in the body. The aorta and arteries were first named air vessels by Greek anatomists, because until the time of Galen they were supposed to contain air instead of blood. The aorta arises from the left ventricle of the heart, ascends a short distance toward the neck, and then curves obliquely backward and toward the left in a semicircular bend, at the level of the second dorsal vertebra, forming the "arch of the aorta." It then passes downward through the posterior part of the chest and abdomen, to the point where it divides into the two common iliac arteries, which are each in turn divided on either side into an internal branch, ramifying into the lower regions of the trunk, and an external branch, descending to the lower limbs. The carotids arise from the arch of the aorta to supply the head and face, and the subclavian arteries derive from the same arch, to supply the different regions of the neck and the upper limbs.

Numerous large arteries arise from the aorta or main trunk as it descends from the upper to the lower portions of the trunk; and these divide again into innumerable branches as they ramify minutely and extensively within the body.