The
ascending aorta (AAo) is a portion of the
aorta commencing at the upper part of the base of the
left ventricle, on a level with the lower border of the third costal cartilage behind the left half of the
sternum; it passes obliquely upward, forward, and to the right, in the direction of the heart’s axis, as high as the upper border of the second right
costal cartilage, describing a slight curve in its course, and being situated, about behind the posterior surface of the
sternum. The total length is about .