Aorta, the main arterial trunk of the body. It rises from the left ventricle of the heart, and after forming an arch across the chest, descends in front of the vertebral column until it reaches the level of the fourth lumbar vertebra, where it divides into the two common iliac arteries. It gives off branches in its course, which supply the head, neck, arms, and trunk, while the iliacs, its terminal divisions, supply the pelvis and lower limbs. At the junction of the aorta and left ventricle are the aortic or semi-lunar valves, which only allow of the passage of blood from the ventricle into the aorta, and prevent a flow in the opposite direction from occurring. Just above the aortic valves are the coronary arteries, by means of which the heart itself is supplied with arterial blood. The aorta is subject to various diseases,, notably to aneurism (q.v.) and atheroma (q.v.).