A metarteriole is a short
microvessel
The microcirculation is the circulatory system, circulation of the blood in the smallest blood vessels, the microvessels of the microvasculature present within organ (anatomy), organ Tissue (biology), tissues. The microvessels include terminal ar ...
in the
microcirculation that links
arteriole
An arteriole is a small-diameter blood vessel in the microcirculation that extends and branches out from an artery and leads to capillary, capillaries.
Arterioles have vascular smooth muscle, muscular walls (usually only one to two layers of smoo ...
s and
capillaries.
Instead of a continuous
tunica media
The tunica media (Neo-Latin "middle coat"), or media for short, is the middle tunica (layer) of an artery or vein. It lies between the internal elastic lamina of the tunica intima on the inside and the tunica externa on the outside.
Artery
The ...
, 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.
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.
References
External links
Histology at uni-mainz.de
Arteries
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