Abdominal aortic aneurysm. Gross specimen of a longitudinal section through an abdominal aorta with an aneurysm (swelling). The aorta is the main artery that supplies blood from the heart to most parts of the body. The swelling (along much of this section) is due to weakening of the wall of the artery, in this case caused by atherosclerosis, the deposition of fatty plaques of atheroma on the inside of the vessel. The weakened walls swell under the pressure of arterial blood. If an aneurysm ruptures, death often results from massive internal bleeding. The aneurysm can be surgically repaired by grafting a reinforcing implant to replace the weakened part of the artery.