The ascending aorta is the first part of the aorta superior to the aortic valve. It is about 4-6cm long. Its lumen is in continuity with the left ventricle inferiorly and the arch of the aorta superiorly.
Immediately superior to each of the three aortic valve leaflets, it is dilated to form a sinus. With ascent superiorly from the leaflets, the amount of collagen in the aortic wall decreases while the amount of elastic tissue increases. From the right and left sinuses the right and left coronary arteries emerge; these are the only branches of the ascending aorta.
Initally, the ascending aorta runs superiorly and slightly anteriorly. Then, it curves posteriorly and to the left to join the arch of the aorta.
The structure of the wall of the ascending aorta is that of a large elastic artery. Externally, it is coated with a layer of fibrous pericardium for the majority of its course.