Intestinal villus
Micrograph of the small intestine mucosa showing intestinal villi - top half of image. H&E stain Image2 = Gray1058.png
Latin	villi intestinales GraySubject = 248 GrayPage = 1174

Intestinal villi (singular: villus) are tiny, finger-like projections that are approximately 0.5-1mm in length and come out from the wall of the small intestine and have additional extensions called microvilli (singular: microvillus) which protrude from epithelial cells lining villi. They increase the absorptive area and the surface area of the intestinal wall. It is important that the food is absorbed at a considerably fast rate so as to allow more food to be absorbed. (If the process is too slow, the concentration of the blood in the blood vessels and the food will be equal, thus, diffusion will not occur.) Digested nutrients (including sugars and amino acids) pass into the villi through diffusion. Circulating blood then carries these nutrients away.^[1]

[edit] Function

In all humans, the villi and microvilli together increase intestinal absorptive surface area 30-fold and 600-fold, respectively, providing exceptionally efficient absorption of nutrients in the lumen. This increases the surface area so there are more places for food to be absorbed.

There are also enzymes on the surface for digestion. Villus capillaries collects amino acids and simple sugars taken up by the villi into the blood stream. Villus lacteals (Lymph capillary) collect absorbed chylomicrons, which are lipoproteins composed of triglycerides, cholesterol and amphipathic proteins, and are taken to the rest of the body through the Lymph fluid.

[edit] Additional images

Different stages of coeliac disease

Structure of a villus

Microvilli(shaggy hair) show electron dense plaques (open arrow) at their apices. These plaques may be the anchoring point for the microfilaments which run up through the core of the microvilli. While an extensive glycocalyx is present on the microvilli of many mammals, the microvilli observed in this study do not demonstrate any visible glycocalyx. The junctional complex (thin arrow) at the apices of the epithelial cells is supplemented by numerous spot desmosomes (arrow head) on the lateral surfaces of the cells.

[edit] References

[edit] External links

• Histology at BU 11504loa – "Digestive System: Alimentary Canal: pyloro/duodenal junction, duodenum"
• Histology at BU 11513loa – "Digestive System: Alimentary Canal: pyloro/duodenal junction"
• Histology at BU 11609loa – "Digestive System: Alimentary Canal: duodenum, plicae circularis"
• Intestinal+villi at eMedicine Dictionary