FRANCIS LEROY & MARC URLUS, BIOCOSMOS / SCIENCE PHOTO LIBRARY FRANCIS LEROY & MARC URLUS, BIOCOSMOS / SCIENCE PHOTO LIBRARY
Regulation of blood flow. Animation showing how precapillary sphincters (green) can regulate blood flow. Sphincters are bands of smooth muscle around a passage or orifice. Precapillary sphincters are found at the part of the capillary that originates at the arteriole. If they contract, blood flow is reduced and if they relax blood flow is increased. They are important in the regulation of temperature. In cold conditions the body reduces blood flow to the skin to stop heat loss, while in hot conditions it does the opposite.
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