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Capillary
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The capillary sits at the transition point between two small vessels: the arteriole and the venule. That is where exchange happens. Nutrients and metabolites, the substances the body makes and uses up, leave the blood and move into the interstitium, the space between the cells, and the cells pick them up.
Its wall is a single layer of flat cells, what histology calls simple squamous epithelium, resting on a basement membrane and dotted with a few scattered cells called pericytes. That is why the comparison that helps most is a garden hose against a sheet of wet paper. And the flow of blood entering that stretch is governed mainly by small rings of muscle, the precapillary sphincters. Capillaries are spread throughout the body, doing the same job in every tissue.
In brief
The capillary is the transition point between an arteriole and a venule, and this is where exchange happens: its thin wall delivers nutrients and metabolites into the interstitium for cells to take up.
That wall is made of a single layer of simple squamous epithelium, a basement membrane and a few scattered pericytes; blood entry is controlled mainly by precapillary sphincters.
It is the difference between a garden hose and a sheet of wet paper.
Capillaries are distributed throughout the body and do this work in every tissue.
Sources (1)
- National Center for Biotechnology InformationHistology, Capillary. StatPearls
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
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