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Capillaries Arteries and Veins

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Capillaries, Arteries and Veins

There are three main types of blood vessels: * arteries take blood away from the heart to the body organs and tissues. The artery wall is thick and muscular so it can withstand the high pressure of the blood being pumped directly from the heart. The main artery is the aorta. * capillaries are tiny, thin-walled vessels which form a network to take blood through the organs and tissues * veins collect blood from the capillaries in the body and return the blood to the heart. The wall of the veins are thin, the blood is at a much lower pressure. To prevent the backflow of this lower pressure blood the veins contain valves.

The function of capillaries is to allow food and oxygen to diffuse to cells while waste is diffused from cells. Capillaries have thin walls - only one cell thick - that allow them to effectively perform their function and they are composed of a single layer of endothelial cells, which are very thin flattened cells that line the inner walls of all of the blood vessels, this enables substances to efficiently diffuse. Capillaries extend and branch into every tissue of your body, ensuring that every cell has a blood supply. It is here, in the capillary beds, that your cells pick up oxygen and nutrients and drop off carbon dioxide and wastes. It is the smallest blood vessel. Capillaries are tiny (extremely narrow) blood vessels, of approximately 5-20 micro-metres
(one micro-metre = 0.000001metre) diameter.
There are networks of capillaries in most of the organs and tissues of the body. These capillaries are supplied with blood by arterioles and drained by venules. With the exception of the lungs, where the opposite is true, capillaries bring oxygenated blood, blood carrying oxygen, to organs and carry away deoxygenated blood, blood with the oxygen removed. Contains blood at low pressure...

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