Editing Intestinal villus

{{short description|Finger-like projection of the small intestine}}
{{Infobox anatomy
| Name        = Intestinal villus
| Latin       = villi intestinales
| Greek       = 
| Image       = Small intestine low mag.jpg
| Caption     = [[Micrograph]] of the [[small intestine]] [[mucosa]] showing '''villi''' – top half of image. [[H&E stain]]
| Width       = 300
| Image2      = Gray1058.png
| Caption2    = Section of duodenum of a cat. X 60.
| Precursor   = 
| PartOf      = [[Gastrointestinal wall|Wall]] of [[small intestine]]
| System      = [[Digestion|Digestive system]]
| Artery      = 
| Vein        = 
| Nerve       = 
| Lymph       = 
}}
'''Intestinal villi''' ({{Singular}}: '''villus''') are small, finger-like projections that extend into the [[lumen (anatomy)|lumen]] of the [[small intestine]]. Each villus is approximately 0.5–1.6&nbsp;mm in length (in humans), and has many [[microvillus|microvilli]] projecting from the [[enterocytes]] of its [[epithelium]] which collectively form the striated or [[brush border]]. Each of these microvilli are about 1 μm in length, around 1000 times shorter than a single villus. The intestinal villi are much smaller than any of the [[circular folds]] in the intestine. 

Villi increase the internal surface area of the intestinal walls making available a greater surface area for absorption. An increased absorptive area is useful because digested nutrients (including monosaccharide and [[amino acid]]s) pass into the semipermeable villi through diffusion, which is effective only at short distances.  In other words, increased surface area (in contact with the fluid in the lumen) decreases the average distance travelled by nutrient molecules, so effectiveness of diffusion increases. The villi are connected to the blood vessels so the circulating blood then carries these nutrients away.

==Structure==

===Microanatomy===
<gallery>
File:Gray1059.png|Vertical section of a villus from the dog's small intestine. X 80. (Simple columnar epithelium labeled at right, third from top.)
File:Gray1060.png|Transverse section of a villus, from the human [[intestine]]. X 350.<br />a. [[Basement membrane]], here somewhat shrunken away from the epithelium.<br />b. [[Lacteal]].<br />c. [[Columnar epithelium]].<br />d. Its striated border.<br />e. [[Goblet cells]].<br />f. [[Leucocytes]] in epithelium.<br />f’. Leucocytes below epbithelium.<br />g. [[Blood vessel]]s.<br />h. [[Muscle cells]] cut across.
File:Cross-section histology of small intestinal villi of the terminal ileum.jpg|Cross-section histology of small intestinal villi of the human [[terminal ileum]].
File:MCT Chicken jejunum oblique.jpg|[[X-ray microtomography|MicroCT]]-based volume projection of the jejunal mucosa of a chicken. Virtual volume block with vertically truncated villi in oblique view. Scalebar = 0.2 mm.
File:MCT Chicken jejunum horizontal cut.jpg|MicroCT-based volume projection of the jejunal mucosa of a chicken. Virtual horizontal cut through villi. Scalebar = 0.2 mm.
</gallery>

[[Enterocytes]], along with [[goblet cells]],  represent the principal cell types of the [[epithelium]] of the villi in the small intestine.<ref name=cytokines>{{Cite web|url=http://www.copewithcytokines.org/cope.cgi?key=Paneth%20cells|title=Paneth cells (Cytokines & Cells Encyclopedia - COPE)}}</ref>

==Function==
There, the villi and the microvilli increase intestinal absorptive surface area approximately 40-fold and 600-fold, respectively, providing exceptionally efficient absorption of [[nutrient]]s in the [[lumen (anatomy)|lumen]].<ref name="Oral Delivery of Macromolecular Drugs: Barriers, Strategies and Future Trends">{{cite book|url=https://www.springer.com/biomed/pharmacology%20&%20toxicology/book/978-1-4419-0199-6|title=Oral Delivery of Macromolecular Drugs - Barriers |author=Andreas Bernkop-Schnürch |editor1-first=Andreas |editor1-last=Bernkop-Schnürch |year=2009 |publisher=Springer|doi=10.1007/978-1-4419-0200-9 |isbn=978-1-4419-0199-6 }}</ref> 

There are also [[enzyme]]s (enterocyte digestive enzyme) on the surface for [[digestion]]. Villus capillaries collect [[amino acid]]s and simple sugars taken up by the villi into the blood stream. Villus [[lacteal]]s ([[lymph capillaries]]) collect absorbed [[chylomicron]]s, which are lipoproteins composed of triglycerides, [[cholesterol]] and amphipathic proteins, and are taken to the rest of the body through the [[lymph]] fluid.

Villi are specialized for absorption in the small intestine as they have a thin wall, one cell thick, which enables a shorter diffusion path. They have a large surface area so there will be more efficient absorption of fatty acids and glycerol into the blood stream. They have a rich blood supply to keep a concentration gradient.<ref name="Science Aid:Digestive System">{{cite web|url=http://scienceaid.co.uk/biology/humans/digestion.html|title=Digestion: Digestive System, Enzymes, Absorption in the Small Intestine|access-date=2014-12-30|archive-url=https://web.archive.org/web/20161118053805/http://www.scienceaid.co.uk/biology/humans/digestion.html|archive-date=2016-11-18|url-status=dead}}</ref>

<gallery>
File:Intestinal villus simplified.svg|Structure of a villus (see reference quoted in text)
</gallery>

==Clinical significance==

===Villous atrophy===
[[File:Coeliac Disease.png|thumb|Different stages of coeliac disease]]
In diseases of the small intestine the villi can become flattened due to the effects of inflammation, and the villi can sometimes disappear. This deterioration is known as villous atrophy, and is often a feature of [[coeliac disease]].<ref name="Coeliac">{{cite web |title=Causes |url=https://www.coeliac.org.uk/information-and-support/coeliac-disease/about-coeliac-disease/causes/ |website=Coeliac UK |access-date=12 July 2020 |language=en}}</ref>

==Additional images==
<gallery>
File:Nudemousejejunum EM.jpg|[[Microvilli]] (shaggy hair) show electron dense plaques (open arrow) at their apices.
</gallery>

==References==
{{Reflist}}

==Further reading==
* C. W. Chan, Y. K. Leung and K. W. Chan (2014). "Microscopic anatomy of the vasculature of the human intestinal villus - a study with review". ''European Journal of Anatomy'', 18 (4): 291–301.

{{Digestive tract}}

{{Authority control}}
[[Category:Small intestine]]