What are blood vessels?
blood vessels are part of the circulatory system that passes through nutrients, blood, hormones and other important substances to and from body 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 blood. Tits carry oxygenated blood from the heart to all structures of the body. The capillaries are very small, permeable blood vessels in which water and chemicals between blood and body are changed. The veins carry deoxygenated blood from the capillaries back to the heart.
The arteries and veins have the same structure. They are composed of three layers: tuns Intima, Tunica Media and Tunica Adventitia. Intima tuna in the innermost layer and thinnest. It consists of a layer of simple spinocellic endothelium with layer tissue below it.
Medium tunica media is the strongest layer of blood vessels. It contains elastic fibers, connective tissue and smooth muscle in some blood vessels. Smooth musclethe size of the blood vessel; For example, it can enlarge a specific container if a particular area requires increased blood supply. The spread of blood vessels in called vasodilation, while narrowing of the blood vessels is called vasoconstriction. Both processes are controlled by an autonomic nervous system and are not under conscious.
Tunica Adventitia is the farthest layer of veins and springs. It consists of connective tissue without epithelium. In larger blood vessels, it also contains nerves and capillaries, called vaso vasorum.
capillaries have a much simpler structure than arteries and lives. Usually there are a layer of simple spinocellular epithelium, although some also have connective tissue. The capillaries must be very small to allow nutrients to be replaced between blood and body tissues.
Small arteries leading to capillaries are called arteriols, while small veins leading from capillaries are called venules. The largest artery that leads from the heart, there is aorta, while the largest vein that carries blood into the heart is the Cava. The pulmonary artery and lung vein, which are blood vessels leading to the lungs and lungs, are the only artery bearing deoxygenated blood and the only vein bearing oxygenated blood in the body.