Chapter 93: Diseases of the Aorta
The aorta is an elastic artery with a trilaminar wall. Which of the following statements is incorrect regarding the layers that make up the aorta?
A. The innermost lining of the tunica intima is the endothelium
B. An internal elastic membrane forms the outer lining of the tunica intima
C. Within the tunica adventitia lie the nervi vasorum and vasa vasorum
D. The vasa vasorum develops into a capillary network supplying the adventitia and media of the abdominal aorta
E. The tunica media is comprised of elastin, smooth muscle cells, collagen, and ground substance
The answer is D. (Hurst’s The Heart, 14th Edition, Chap. 93) The vasa vasorum supplies the adventitia and media of the thoracic aorta (the vasa vasorum do not supply the media of the abdominal aorta). The major conductance vessel of the body, the aorta is an elastic artery with a trilaminar wall: the tunica intima, tunica media, and tunica adventitia.1,2 The innermost lining of the tunica intima is the endothelium, resting on a thin basal lamina (option A). An internal elastic membrane forms the outer lining of the tunica intima (option B). The tunica media is approximately 1 mm thick, comprised of elastin, smooth muscle cells, collagen, and ground substance (option E). The predominance of elastic fibers in the aortic wall and their arrangement as circumferential lamellae distinguish it from the smaller muscular arteries. Surrounding the tunica media is the tunica adventitia, which is composed of loose connective tissue, including fibroblasts, relatively small amounts of collagen fibers, elastin, and ground substance. The adventitia strengthens the aorta and is essential to aortic surgeons for secure suturing of tissues. Within the tunica adventitia lie the nervi vasorum and vasa vasorum. Unlike the elastic fibers of the arterial wall, which are highly distensible, collagen is inelastic and provides the tensile strength required to prevent deformation and rupture of the aortic wall.
A 75-year-old man who smokes and is known for hypertension presents to the emergency department with chest pain. Troponins are mildly positive, but the electrocardiogram does not demonstrate acute ischemia. CT angiography of the aorta is performed, which reveals a contrast-filled pouch-like protrusion in the thoracic aorta, in the absence of an intimal flap or false lumen. A transesophageal echocardiogram confirms a localized, crater-like protrusion of the aortic lumen into the aortic wall. Which of the following best represents the diagnosis?