Figure 4.

Cellular organization of different types of blood vessels. Blood vessels of different sizes, ranging from elastic (e.g. aorta and pulmonary artery) and muscular (e.g. femoral and radial artery) arteries via arterioles to capillaries and further on to venules and veins, are depicted. The cellular organization of endothelial and mural cells (VSMCs and pericytes) of the differently sized vessels is shown in cross-section. Note that muscular arteries contain more VSMCs in the tunica media than elastic arteries. Arterioles have a VSMC coat but largely lack elastic tissue. Capillaries have a single EC layer and are covered by pericytes rather than VSMCs. Venules and veins are thin walled and less elastic than arteries.