Intestinal villus:
| Intestinal villus |
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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. |
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| Section of duodenum of cat. X 60. |
| Latin |
villi intestinales |
| Gray's |
subject #248 1174 |
Intestinal villi (singular: villus) are tiny, finger-like projections that 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 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 collects amino acids and simple sugars taken up by the villi into the blood stream. Villus lacteals (Lymph capillary) collects absorbed fatty acids, which are reconstructed into triglycerides, combined with cholesterol and amphipathic proteins to form chylomicrons, and are taken to the rest of the body through the Lymph fluid.
[edit] 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.
[edit] Additional images
different stages of Coeliac Disease
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[edit] References
- ^ [1] Tiscali UK - Reference encyclopedia
[edit] External links
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