In order to understand plaque formation and plaque composition it is necessary to have a knowledge of the normal histology. In general, arteries contain three concentric layers: the intima, media and ...adventitia (Fig. 4.1.1). The intima consists of a single layer of endothelial cells with only a small amount of underlying connective tissue. The intima is separated from the media by a thick layer of elastic fibers called the intern elastic lamina. The media is mostly composed of smooth muscle cells. Approximately the inner half of the smooth muscle cell layer receives its nutrients from the lumen via diffusion. The outer half, however, needs nourishment from blood vessels themselves, called the vasa vasorum, which course into the media from the adventitia. Between the media and the adventitia lies the external elastic lamina. The adventitia consists of connective tissue, nerve fibers and the vasa vasorum.
Fig. 4.1.1.Micrograph showing a normal muscular artery with a single layer thick intima (I), the media (M, arrows mark the borders) and adventitia (A)
