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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. Microvilli are approximately 100 nanometers in diameter and their length varies from approximately 100 to 2,000 nanometers.
The destruction of microvilli can actually be beneficial sometimes, as in the case of elimination of microvilli on white blood cells which can be used to combat auto immune diseases. [ 6 ] Congenital lack of microvilli in the intestinal tract causes microvillus atrophy , a rare, usually fatal condition found in new-born babies.
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 nuclei are located closer along the basal side of the cell. [1] 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.
The brush border on the apical surface of the epithelial cells is covered with glycocalyx, which is composed of oligosaccharides attached to membrane glycoproteins and glycolipids. [7] TEM image of a thin section cut through an epithelial cell showing the luminal surface (apical end) of the cell packed with microvilli that make up the absorbing ...
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 .
The nuclei of the cells (located at the outer edges of the cells lining the walls of the crypts) are stained blue-gray with haematoxylin. As seen in panels C and D, crypts are about 75 to about 110 cells long. The average crypt circumference is 23 cells. [8] From the images, an average is shown to be about 1,725 to 2530 cells per colonic crypt.
The microvilli create a brush border that increases the area for absorption. In the ileum there are occasionally Peyer's patches in the lamina propria. Brunner's glands are found in the duodenum but not in other parts of the small intestine.