Arteries are blood vessels that transport oxygenated blood from the heart to other organs and systems throughout the body.

A typical artery contains an elastic arterial wall that can be divided into three principal layers, although the absolute and relative thickness of each layer varies with the type or diameter of artery. The outer layer is termed the tunica adventia, the middle layer is termed the tunica media, and an inner layer is the tunica intima. These layers surround a lumen, or opening, that varies in size with the particular artery, through which blood passes.

Arteries of varying size comprise a greater arterial blood system that includes, in descending diameter, the aorta, major arteries, smaller arteries, arterioles, metaarterioles, and capillaries. It is only at the level of the capillary that branches of arteries become thin enough to permit gas and nutrient exchange. As the arterial system progresses toward...