Thoracic aorta

The thoracic aorta is defined as the portion of the aorta that extends from the aortic valve to the diaphragm and is anatomically divided into four segments: the aortic root (including the aortic valve annulus, valve cusps, and sinuses of Valsalva), the ascending aorta (from the sinotubular junction to the origin of the brachiocephalic artery), the aortic arch (from the brachiocephalic artery origin to the left subclavian artery, giving rise to the head and neck vessels), and the descending thoracic aorta (from the left subclavian artery to the diaphragm).

Note that in the Terminologia Anatomica 2 , the thoracic aorta is defined as the thoracic part of descending aorta, and does not include the ascending aorta and aortic arch.

The thoracic aorta is structurally composed of three layers: the intima (endothelial layer), media (concentric elastic fibers and smooth muscle), and adventitia (collagen, vasa vasorum, and nerves), which are critical for its function and integrity.