Microvilli

Microvilli are stable extensions of the plasma membrane produced by the close packing of actin filaments by villin and fimbrin which are short cross-linking proteins. If villin or fibrin are over-expressed in a fibroblast they will make microvilli! Microvilli increase the surface area of many cells, usually in polarised epithelia, like the epithelium of the intestine (up to 20 fold). This also nutrients to be absorbed more efficiently. The side arms linking the filaments to the membrane are myosin I and calmodulin