American Board of Pathology (ABPath) Practice Test

The media is the thickest layer of an artery due to its composition and function. This layer consists primarily of smooth muscle cells and elastic fibers, which play a critical role in regulating blood pressure and flow. The smooth muscle allows for vasoconstriction and vasodilation, processes necessary for maintaining adequate blood circulation and responding to varying physiological demands.

In contrast, the intima, which is the innermost layer of the artery, consists of a single layer of endothelial cells and a small amount of connective tissue, making it relatively thin. The adventitia, or the outer layer, primarily provides structural support and houses larger blood vessels and nerves, but it does not have the same capacity for muscle contraction as the media. The endothelium is a part of the intima and is also not thick, being a single layer of cells. Hence, the media’s significant thickness is essential for the dynamic functions of arteries in the cardiovascular system.