•Capillaries are microscopic blood vessels with extremely thin walls. Only the tunica intima is present in these walls, and some walls consist exclusively of a single layer of endothelium. Capillaries penetrate most body tissues with dense interweaving networks called capillary beds. The thin walls of capillaries allow the diffusion of oxygen and nutrients out of the capillaries, while allowing carbon dioxide and wastes into the capillaries.Below is a list of the different types of capillaries:•Metarterioles (precapillaries) are the blood vessels between arterioles and venules. Although metarterioles pass through capillary beds with capillaries, they are not true capillaries because metarterioles, like arterioles, have smooth muscle present in the tunica media. The smooth muscle of a metarteriole allows it to act as a shunt to regulate blood flow into the true capillaries that branch from it. The thoroughfare channel, the tail
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