Microcirculation deals with the circulation of blood from the heart to arterioles (small arteries), to capillaries, to venules (small veins) and back to the heart. A vessel called a thoroughfare channel allows blood to flow freely between an arteriole and a venule. Capillaries extend from this channel and structures called precapillary sphincters control the flow of blood between the arteriole and capillaries.
The precapillary sphincters contain muscle fibers that allow them to contract. When the sphincters are open, blood flows freely to the capillary bed where fluids, gasses, nutrients, and wastes are exchanged between the blood and body cells. It is important to note that blood is supplied to all parts of the body at all times, but all capillary beds do not contain blood at all times. Blood is diverted to the parts of the body that need it most at a particular time. For more information on microcirculation and blood flow visit the Blood Vessels page.
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