Most cells need to be within a few cell-widths of a capillary to stay alive, and the cells that make up the outer walls of a blood vessel are no exception. The network of smaller vessels that supply these cells is known as the vasa vasorum. The vasa vasorum penetrates the tunica adventitia, as well as the deeper tunica media of larger vessels such as the aorta.

The vasa vasorum consists of a network of arterioles, capillaries and venules, depending on the vessel. They provide the vessel wall that they penetrate with metabolites which they would otherwise not receive due to the thickness of the layers making up the wall. The vasa vasorum is present more frequently in veins than in arteries.

Vasa vasorum