Venule
619442
222538595
2008-06-29T21:54:09Z
Udo.schroeter
7128480
[[Image:Illu_capillary.jpg|thumb|300px]]
A '''venule''' is a small [[blood vessel]] that allows deoxygenated [[blood]] to return from the [[capillary]] beds to the larger blood vessels called [[vein]]s.
Venules are blood vessels that drain blood directly from the capillary beds. Many venules unite to form a vein.
==Structure==
Venule walls have three layers: An inner [[endothelium]] composed of squamous [[Endothelium|endothelial cell]]s that act as a [[biological membrane|membrane]], a middle layer of muscle and elastic tissue and an outer layer of [[fibrous connective tissue]]. The middle layer is poorly developed so that venules have thinner walls than [[arterioles]]. These vessels are pink sometimes due to the high content of nitrogen.
In contrast to regular venules, [[high endothelial venules]] are a special type of venule where the endothelium is made up of [[simple cuboidal]] cells. Lymphocytes re-enter the bloodstream through the HEVs.
==External links==
* {{MeshNumber|A07.231.432.952|Venules}}
{{circulatory-stub}}
{{Cardiovascular_system}}
[[Category:Cardiovascular system]]
[[bs:Venula]]
[[de:Venole]]
[[es:Vénula]]
[[it:Venula]]
[[nds:Venool]]
[[pt:Vénula]]
[[ru:Венулы]]