Blood vessel between the blood and the tissues; and the veins, which carry blood from the capillaries back toward the heart. The word "vascular", meaning relating to the blood vessels, is derived from the Latin "vas", meaning vessel. A few structures (such as cartilage and the lens of the eye) do not contain blood vessels and are labeled. The arteries and veins have three layers. The middle layer is thicker in the arteries than it is in the veins: Capillaries consist of little more than a layer of endothelium and occasional connective tissue. When blood vessels connect to form a region of
Vasa vasorum Vasa vasorum The vasa vasorum is a network of small blood vessels that supply the walls of large blood vessels, such as elastic arteries (e.g. aorta) and large veins (e.g. venae cavae). The name derives . Studies conducted with 3-dimensional microcomputed tomography (3D Micro-CT) on pig and human arteries from different vascular beds have shown that there are three different types of vasa vasorum: Depending on the type of vasa vasorum, it penetrates the vessel wall starting at the intimal layer (vasa vasorum interna) or the adventitial layer (vasa vasorum externa). Due to higher radial and circumferential pressures within the