A metarteriole is a short microvessel in the microcirculation that links arterioles and capillaries.[1] Instead of a continuous tunica media, they have individual smooth muscle cells placed a short distance apart, each forming a precapillary sphincter 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.[2]

Illustration of a capillary system with metarterioles and precapillary sphincters, as is present in the mesenteric microcirculation.
Anatomical terminology

Metarterioles exist in the mesenteric microcirculation, and the name was originally conceived only to define the "thoroughfare channels " between arterioles and venules. In recent times the term has often been used instead to describe the smallest arterioles directly prior to the capillaries.[1]


  1. Sakai T, Hosoyamada Y (September 2013). "Are the precapillary sphincters and metarterioles universal components of the microcirculation? An historical review". The Journal of Physiological Sciences. 63 (5): 319–31. doi:10.1007/s12576-013-0274-7. PMC 3751330. PMID 23824465.
  2. "Structure and Function of Blood Vessels". Anatomy and Physiology II. Lumen Learning. Retrieved 2019-09-23.

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