Microvilli: Difference between revisions

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Microvilli are tiny hairlike protrusions that extend from the apical surface of some [[Epithelial_cells|epithelial cells]] and many other cells involved in absorption and secretion. They are only tiny structures, at about 0.08 µm in width but due to their vast number they greatly increase surface area for absorption and secretion in cells. 
Microvilli are thin, finger-like projections on the surface of cells and are particularly abundant in [[Epithelial cells|epithelia]], where a large surface area is required for effiecient function.  


Each Microvillus stems from one much larger villus, another hair like protrusion, these are between 0.5 and 1.6mm in length. 
 
 
Each microvilli has about 20-30 parrellel [[Actin filaments|actin filaments]] that extend from the tip into the cell cortex. In all the actin filaments the plus ends point away from the cell body and are held together by actin-bundling proteins- the most important of which is villin, a protein that is specific to microvilli and cross-links actin filaments into tight bundles.
 
 
 
At the base of each microvillus, the actin filaments are anchored into a specialized region known as the terminal web, which contains and concentrated net-work of spectrin molecules and a layter of intermediate filaments. It is thoughyt that spectrin imparts rigidity to the cell cortex; because the actin filaments are anchored to the terminal web, this keeps the microvilli orientated perpendicularly to the apical surface of the cell.&nbsp;The actin filaments are attacted to the plasma membrane by lateral bridges composed of myosin-I and serveral other molecules including the Ca2+. <ref>G M. Fuller and D, Shiels. Molecular Basis of Medical Cell Biology (1998) 1st edition. Chapter 7 PP.140-141</ref>
 
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= Reference  =
 
<references />

Revision as of 12:55, 29 November 2013

Microvilli are thin, finger-like projections on the surface of cells and are particularly abundant in epithelia, where a large surface area is required for effiecient function.

 

Each microvilli has about 20-30 parrellel actin filaments that extend from the tip into the cell cortex. In all the actin filaments the plus ends point away from the cell body and are held together by actin-bundling proteins- the most important of which is villin, a protein that is specific to microvilli and cross-links actin filaments into tight bundles.

 

At the base of each microvillus, the actin filaments are anchored into a specialized region known as the terminal web, which contains and concentrated net-work of spectrin molecules and a layter of intermediate filaments. It is thoughyt that spectrin imparts rigidity to the cell cortex; because the actin filaments are anchored to the terminal web, this keeps the microvilli orientated perpendicularly to the apical surface of the cell. The actin filaments are attacted to the plasma membrane by lateral bridges composed of myosin-I and serveral other molecules including the Ca2+. [1]


Reference

  1. ↑ G M. Fuller and D, Shiels. Molecular Basis of Medical Cell Biology (1998) 1st edition. Chapter 7 PP.140-141
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