Tags: Anatomical Structure.
A precapillary sphincter is a band of smooth muscle that adjusts blood flow into capillaries mainly in the mesenteric microcirculation. At the point where each of the capillaries originates from an arteriole a smooth muscle fiber encircles the capillary. This is called the precapillary sphincter. The sphincter can open and close the entrance to the capillary by which contraction causes blood flow in a capillary to change as vasomotion occurs.
