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There are two types of blood vessels in the circulatory system of the body: arteries that carry oxygenated blood from the heart to various parts of the body and veins that carry blood towards the heart for purification.hey are tiny branches of arteries that lead to capillaries and help maintain the pressure and blood flow in the body. Venous valves prevent blood from flowing in the opposite direction. Connective tissues make up the outermost layer of a vein which is also known as-tunica adventitia or tunica externa.
Veins have the same three layers as arteries and are elastic, but they have a less-muscular middle layer, making their walls thinner. Also, unlike arteries, some veins have valves (tissue flaps) that permit blood to flow in only one direction, back to the heart.rteries carry blood away from the heart; capillaries reach all of the body's seventy trillion cells; and veins carry blood back to the heart. Because blood vessels form a circular route, this system is also called the circulatory system.