Precapillary sphincter

Precapillary sphincter is a band of smooth muscle that adjusts the blood flow into capillaries primarily in the microcirculation. The precapillary sphincters, composed of smooth muscle cells, are located at the arteriolar end of capillaries. These sphincters regulate blood flow by constricting and dilating. When the precapillary sphincters are closed, blood is shunted away from the capillaries directly into the venules.

Structure

The precapillary sphincter is a ring-like band of smooth muscle that is capable of contracting or dilating to regulate the blood flow into a capillary. It is located at the arteriolar end of the capillary, effectively serving as a gateway for blood to enter the capillary.

Function

The primary function of the precapillary sphincter is to regulate blood flow into the capillaries. This is achieved by the contraction and dilation of the sphincter. When the body is at rest, the precapillary sphincters are usually in a half-open state. However, they can close completely under certain conditions, such as during vasoconstriction or when the body's tissues do not require additional oxygen or nutrients.

Clinical significance

Abnormal function of the precapillary sphincters can lead to a variety of health problems. For example, if the sphincters do not properly dilate, it can lead to hypertension (high blood pressure). Conversely, if the sphincters do not properly constrict, it can lead to hypotension (low blood pressure).

See also

• Arteriole
• Capillary
• Microcirculation
• Vasoconstriction
• Vasodilation

Precapillary sphincter Resources
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