Intestinal villus

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Intestinal villus
Nudemousejejunum EM.jpg
Microvilli 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.
Gray1058.png
Section of duodenum of cat. X 60.
Latin villi intestinales
Gray's subject #248 1174
Dorlands/Elsevier v_08/12857047

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Overview

Intestinal villi (singular: villus) are tiny, finger-like structures that protrude from the wall of the intestine and have additional extensions called microvilli (singular: microvillus) which protrude from epithelial cells lining villi. They increase the absorptive 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]

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 of the intestine to around the area of a small parking lot or a tennis court.

There are also enzymes on the surface for digestion. Villus capillaries collect amino acids and simple sugars taken up by the villi into the blood stream. Villus lacteals collect absorbed fatty acids.

Homologue of alveolus

Villi serve the same purpose as the alveoli in the lungs. Both increase surface area, which helps to increase the transfer rate of nutrients into the blood through diffusion, although alveoli also transfer wastes out. Alveoli transfer carbon dioxide out and oxygen into the bloodstream, while villi transfer digested food in.

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References

  1. [1] Tiscali UK - Reference encyclopedia

External links

  • Histology image: 11504loa – Histology Learning System at Boston University - "Digestive System: Alimentary Canal: pyloro/duodenal junction, duodenum"
  • Histology image: 11513loa – Histology Learning System at Boston University - "Digestive System: Alimentary Canal: pyloro/duodenal junction"
  • Histology image: 11609loa – Histology Learning System at Boston University - "Digestive System: Alimentary Canal: duodenum, plicae circularis"
  • Histology at University of Southern California gi/c_36
  • Histology at University of Southern California gi/c_39
  • Intestinal+villi at eMedicine Dictionary

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