Microvillus
In the enterocyte microvillus, the structural core is attached to the plasma membrane along its length by lateral arms made of myosin 1a and Ca2+ binding protein calmodulin.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.The nucleation of actin fibers occurs as a response to external stimuli, allowing a cell to alter its shape to suit a particular situation.Because of this vital function, the microvillar membrane is packed with enzymes that aid in the breakdown of complex nutrients into simpler compounds that are more easily absorbed.[6] Congenital lack of microvilli in the intestinal tract causes microvillus atrophy, a rare, usually fatal condition found in new-born babies.