Skip to Main Content


The aorta has a complex intrinsic biology and sophisticated mechanical properties involving intrinsic relaxation and contraction that interact with left ventricular ejection to enhance hemodynamic function. 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 (Fig. 106–1).1,2 The innermost lining of the tunica intima is the endothelium, resting on a thin basal lamina. The subendothelial tissue comprises fibroblasts, collagen fibers, elastic fibers, and mucoid ground substance. An internal elastic membrane forms the outer lining of the tunica intima. The tunica media is approximately 1 mm thick, comprising elastin, smooth muscle cells, collagen, and ground substance. The predominance of elastic fibers in the aortic wall and their arrangement as circumferential lamellae distinguish this elastic artery from the smaller muscular arteries. A lamellar unit is made up of two concentric elastic lamellae and the smooth muscle cells, collagen, and ground substance contained within.3,4 The thoracic aorta incorporates 35 to 56 lamellar units and the abdominal aorta about 28 units.5 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 is known to surgeons as the "strength" layer of the aorta and is essential for secure suturing of aortic tissues. Within the tunica adventitia lie the nervi vasorum and vasa vasorum. The arteries arising along the course of the aorta give rise to the vasa vasorum, which develop into a capillary network supplying the adventitia and media of the thoracic aorta. The vasa vasorum do not supply the media of the abdominal aorta. 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.

Figure 106–1.
Graphic Jump Location

Transverse section of the wall of a large elastic artery demonstrating the well-developed tunica media containing elastic lamellae. Pararosaniline–toluidine blue stain; medium magnification. Reproduced with permission from The circulatory system.1.


The ascending aorta is approximately 3 cm in diameter, depending on age, gender, and body surface area. The diameter of the aortic arch is similar. Descending in the posterior mediastinum, the thoracic aorta tapers slightly to about 2 to 2.3 cm. The abdominal aorta narrows to 1.7 to 1.9 cm in its distal portion. The aortas of males are larger than those of females, and aortic root dimension increases with age, height, and weight. The gender difference in aortic root dimension is not entirely explained by body surface area.5


Hemodynamic Function of the Aorta


The force of left ventricular (LV) ejection creates a pressure wave that traverses the aorta, producing radial expansion and contraction of the arterial walls.6 Potential energy derived from myocardial ...

Want remote access to your institution's subscription?

Sign in to your MyAccess profile while you are actively authenticated on this site via your institution (you will be able to verify this by looking at the top right corner of the screen - if you see your institution's name, you are authenticated). Once logged in to your MyAccess profile, you will be able to access your institution's subscription for 90 days from any location. You must be logged in while authenticated at least once every 90 days to maintain this remote access.


About MyAccess

If your institution subscribes to this resource, and you don't have a MyAccess profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus.

Subscription Options

AccessCardiology Full Site: One-Year Subscription

Connect to the full suite of AccessCardiology content and resources including textbooks such as Hurst's the Heart and Cardiology Clinical Questions, a unique library of multimedia, including heart imaging, an integrated drug database, and more.

$595 USD
Buy Now

Pay Per View: Timed Access to all of AccessCardiology

24 Hour Subscription $34.95

Buy Now

48 Hour Subscription $54.95

Buy Now

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.