The Ascending Aorta is the first portion of the aorta from the left ventricle rising to the level of the sternal angle. It continues as the arch of the aorta until it begins its descending thoracic portion.
The Descending Aorta is the continuation of the aortic arch. Superiorly it lies to the left of the midline, and inferiorly it leaves the posterior mediastinum as a midline structure passing behind the crura of the diaphragm. It gives rise to the third through the eleventh posterior intercostal arteries that arch upward to the lower nine intercostal spaces. It gives rise to the bronchial and esophageal arteries. Usually there are two bronchial arteries on the left and one on the right. A second bronchial artery on the right is common; when present it arises from the first aortic intercostal artery (third posterior intercostal).
Aneurysms of the ascending aorta are most commonly the result of dissecting aortic aneurysm that has extended proximally. Aneurysms distal to the ascending aorta most commonly occur secondary to atherosclerosis and can assume varied shapes.