A Metarteriole is a short vessel that links arterioles and venules. Instead of a continuous tunica media, they have individual smooth muscle cells placed a short distance apart, each forming a precapillary sphincter

Precapillary sphincter

The precapillary sphincter is a band of smooth muscle that adjusts the blood flow into each capillary. At the point where each true capillary originates from a metarteriole, a smooth muscle fiber usually encircles the capillary. This is called the precapillary sphincter. This sphincter can open and...

that encircles the entrance to that capillary bed. Constriction of these sphincters reduces or shuts off blood flow through their respective capillary beds. This allows the blood to be diverted to elsewhere in the body.

External links

• Diagram at sci.sdsu.edu
• Histology at uni-mainz.de