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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.
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.
Duodenum with brush border of microvilli. Illustration of the brush border membrane of small intestinal villi. A brush border (striated border or brush border membrane) is the microvillus-covered surface of simple cuboidal and simple columnar epithelium found in different parts of the body.
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.
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.
The terminal web is a filamentous structure found at the apical surface of epithelial cells that possess microvilli.It is composed primarily of actin filaments stabilized by spectrin, which also anchors the terminal web to the apical cell membrane.
Absorptive columnar epithelium is characterized as having a striated border on its apical side, this border is made up of non-motile microvilli allowing for increase surface area for absorption. [1] These are known as non-ciliated columnar epithelium.
When they lack microvilli, they are characterized by their microfolds, and hence receive their commonly known name. These cells are far less abundant than enterocytes . These cells can also be identified by cytoskeletal and extracellular matrix components expressed at the edge of cells or on their cell surfaces, such as actin , villin ...