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The Structure of Blood Vessels

Blood vessels are a portion of the circulatory system that moves blood and necessary nutrients through the body. There are several types of blood vessels with accompanying structures and tasks. While the main function of blood vessels is to transport blood through the body, they also are used for diagnostic measuring of blood pressure and pulse. Blood vessels comprise a large portion of the body with an adult having a vessel length of 100,000 miles long when laid end to end.

  1. Arteries

    • The artery blood vessels are composed of smooth muscle on the inside and a tough layer on the outside. The artery vessel layers are an outer tissue layer, muscular layer in the middle and a layer of epithelial cells on the inside. Arteries run parallel through the body with capillaries attached in a web structure. An artery will relax and contract based on signals from the nervous system. The function of the arteries is to transport oxygenated blood from the heart.

    Arterioles

    • Arterioles are little branches of artery blood vessels that connect to the capillaries. These vessels are smaller versions of the arteries and the same as arteries will relax and contract with signals from the nervous system. The arterioles take the blood from the arteries and transport it to capillaries in the body. Arterioles are the primary regulators of blood pressure and flow.

    Capillaries

    • Capillaries are small blood vessels, very narrow in size, and fragile. The capillaries are grouped in a network or web and found in most organs and tissues of the body. The walls of the capillaries are composed of one layer of epithelial cells which allows for an easy exchange of blood to surrounding tissue. The web-like network of capillaries attaches to arteries and veins. Capillaries also exchange water, oxygen and carbon dioxide to tissues.

    Venules

    • A venule is a very small blood vessel that works to drain blood into the veins from the capillaries. Multiple venules group together and form a vein.

    Veins

    • Veins are a thick structured blood vessel consisting of the same three tissue layers as arteries. A vein is less elastic and thinner than an artery, making it not as strong. Veins have valves that aid in the return of blood to the heart. The valves prevent blood from moving in the wrong or reverse direction. A vein runs parallel through the body with capillaries attached to each. Veins transport blood that is only deoxygenated, meaning it no longer contains oxygen. The pulmonary vein is the only vein in the body that transports oxygenated blood.

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