What is the Anatomy of a Vascular?

Blood vessels are part of the circulatory system, which passes nutrients, blood, hormones, and other important substances to and from the body's cells to maintain homeostasis. Blood vessels are responsible for transporting blood throughout the body. There are three main types of blood vessels: arteries, veins, and capillaries.

Oxygen is the most important nutrient carried by the blood. Arteries carry oxygenated blood from the heart to all body structures. Capillaries are very small, permeable vessels where the exchange of water and chemicals between the blood and body tissues takes place. Blood vessels carry deoxygenated blood from the back of the capillaries to the heart.

Arteries and veins have the same structure. They consist of three layers: tunica intima, tunica media, and tunika adventitia. Intimate tunica in the innermost layer, and thinnest. It consists of a simple squamous endothelium layer, with a lower layer of connective tissue.

Medium tunica media is the thickest layer of blood vessels. It contains elastic fibers, connective tissue, and in some vessels, smooth muscle. Smooth muscle controls the size of blood vessels, for example, can make certain vessels wider if specific areas require increased blood supply. Dilation of blood vessels in what is called vasodilation, while narrowing of the vessels is called vasoconstriction. Both processes are controlled by the autonomic nervous system, and are not under the control of consciousness.

Tunika adventitia is the outermost layer of blood vessels and artieries. It consists of connective tissue, with no epithelium. In larger blood vessels, it also contains nerves and capillaries, called vaso vasorum.

Capillaries are simpler in structure than arteries and veins. They usually consist of simple squamous epithelial layers, although some have connective tissue as well. Capillaries must be very small to allow for the exchange of nutrients between blood and body tissue.

The small arteries that lead to capillaries are called arterioles, while the small blood vessels that lead from capillaries are called venules. The largest artery, which leads from the heart, is the aorta, while the largest vein, which carries blood to the heart, is the vena cava. In the pulmonary arteries and pulmonary veins, which are the blood vessels leading to and from the lungs, respectively, are the only arteries that carry deoxygenated blood and the only veins that carry oxygenated blood in the body.