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Thousands of microvilli form a structure called the brush border that is found on the apical surface of some epithelial cells, such as the small intestines. (Microvilli should not be confused with intestinal villi, which are made of many cells. Each of these cells has many microvilli.)
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 ...
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.
Enterocytes, or intestinal absorptive cells, are simple columnar epithelial cells which line the inner surface of the small and large intestines. A glycocalyx surface coat contains digestive enzymes. Microvilli on the apical surface increase its surface area.
Cells that absorb substances need a large surface area in contact with the substance to be efficient. [7] In intestinal cells, the microvilli are referred to as brush border and are protoplasmic extensions contrary to villi which are submucosal folds, while in the kidneys, microvilli are referred to as striated border. [8]
Micrograph of the small intestine mucosa showing the intestinal villi and crypts of Lieberkühn. The three sections of the small intestine look similar to each other at a microscopic level, but there are some important differences. The parts of the intestine are as follows: This cross section diagram shows the 4 layers of the small intestine wall.
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 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.