![]() The media comprises cellular elements (including smooth muscle cells) and structural proteins (notably elastin and collagen) that form the extracellular matrix (ECM). Most of the mechanical properties of the aorta can be attributed to the media (with the strong collagen component and the stretchable elastin component), although the adventitia is also recognized as a strong layer that maintains aortic diameter and holds stitches when performing surgery on the vessel ( Sanz et al., 2007). The aortic wall, like that of all elastic arteries, has a trilaminar structure consisting of a tunica intima, media, and adventitia. Elefteriades, in Encyclopedia of Cardiovascular Research and Medicine, 2018 Histology and Embryology Because of its delicate structure, the intima is most susceptible to injury. The aortic intima is the thin inner wall layer, characterized histologically by a basement membrane lined with endothelium that is in direct contact with the blood. The media normally accounts for up 80% of the aortic wall thickness and consists of elastic tissue intertwined with muscle fibers. The aortic media is the thick middle layer between the adventitia and intima. Although it is thin, its rich collagen content gives the adventitia the greatest tensile strength of the three aortic wall layers. ![]() The aortic adventitia is the thin outermost collagenous layer that contains the vasa vasorum and nerves. Aortic atherosclerosis injures the intima to cause thickening, calcification, and ulceration. In aortic dissection, the intimal layer separates from the adventitia as the false lumen develops. Diseases such as dissection and atheroma alter aortic wall anatomy. Under normal circumstances, TEE cannot distinguish these layers. The aortic wall consists of three layers: outer adventitia, middle media, and inner intima. Cheung, in Perioperative Transesophageal Echocardiography, 2014 Aortic Wall
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