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Microvilli (sg.: microvillus) are microscopic cellular membrane protrusions that increase the surface area for diffusion and minimize any increase in volume, [1] and are involved in a wide variety of functions, including absorption, secretion, cellular adhesion, and mechanotransduction.
English: Drawing showing the relationship between villi and microvilli of the small intestine. The luminal surface of the enterocytes have microvilli (1 micrometer long) while the cell layer itself is folded to form villi (0.5-1.6 millimeters long) and crypts. Both serve to increase the total absorption surface of the intestine.
Microvilli are approximately 100 nanometers in diameter and their length varies from approximately 100 to 2,000 nanometers. Because individual microvilli are so small and are tightly packed in the brush border, individual microvilli can only be resolved using electron microscopes ; [ 1 ] with a light microscope they can usually only be seen ...
Intestinal villi (sg.: villus) are small, finger-like projections that extend into the lumen of the small intestine.Each villus is approximately 0.5–1.6 mm in length (in humans), and has many microvilli projecting from the enterocytes of its epithelium which collectively form the striated or brush border.
Drawing showing the relationship between villi and microvilli of the small intestine. The luminal surface of the enterocytes have microvilli (1 micrometer long) while the cell layer itself is folded to form villi (0.5-1.6 millimeters long) and crypts. Both serve to increase the total absorption surface of the intestine.
All these villi make for a greater surface area, not only for the absorption of chyme but also for its further digestion by large numbers of digestive enzymes present on the microvilli. The chylomicrons are small enough to pass through the enterocyte villi and into their lymph capillaries called lacteals .
Microvilli are present on the epithelium of a villus and further increase the surface area over which absorption can take place. Numerous intestinal glands as pocket-like invaginations are present in the underlying tissue. In the large intestines, villi are absent and a flat surface with thousands of glands is observed.
Microvilli on the apical surface increase its surface area. This facilitates transport of numerous small molecules into the enterocyte from the intestinal lumen . These include broken down proteins , fats , and sugars , as well as water, electrolytes , vitamins , and bile salts .