Editing Microvillus (section)

==Structure==
Microvilli are covered in plasma membrane, which encloses [[cytoplasm]] and [[microfilaments]]. Though these are cellular extensions, there are little or no cellular [[organelles]] present in the microvilli.

Each microvillus has a dense bundle of cross-linked [[actin]] filaments, which serves as its structural core. 20 to 30 tightly bundled actin filaments are cross-linked by bundling proteins [[fimbrin]] (or plastin-1), [[villin]] and [[Espin (protein)|espin]] to form the core of the microvilli.

In the enterocyte microvillus, the structural core is attached to the plasma membrane along its length by lateral arms made of [[MYO1A|myosin 1a]] and Ca<sup>2+</sup> binding protein [[calmodulin]]. Myosin 1a functions through a binding site for filamentous actin on one end and a lipid binding domain on the other. The plus ends of the actin filaments are located at the tip of the microvillus and are capped, possibly by [[capZ]] proteins,<ref name="books.google.co.il">The Cytoskeleton: Cytoskeleton in specialized tissues and in pathological states, edited by JE Hesketh and IF Pryme, Elsevier, 1996ISBN 1559386894, 9781559386890. Vol3,  pp371, [https://books.google.com/books?id=lyrFRieEw-EC&dq=actin+filaments+capping+in+microvilli+tips&pg=PA371 M1]{{dead link|date=November 2016 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> while the minus ends are anchored in the [[terminal web]] composed of a complicated set of proteins including [[spectrin]] and myosin II.

The space between microvilli at a cell's surface is called the intermicrovillous space. Intermicrovillous space increases with contractile activity of myosin II and [[tropomyosin]], and decreases when contraction ceases.