What are differentiations of the cell membrane?
In some types of cells, the cell membrane presents differentiations that are necessary for the specific functions of the cells. The main differentiations are the microvilli and the structures for reinforcement of adhesion or union between cells (cell junctions). Microvilli are multiple external projections of the membrane resembling glove fingers. This differentiation is found in cells of tissues where it is advantageous to increase the size of the surface area in contact with the exterior, for example, in the enteric (intestinal) epithelium for absorption of nutrients. Membrane differentiations for reinforcement of adhesion between cells occur mainly in epithelial tissues where the need for coverage and impermeability requires cells to be “glued” to neighboring cells. These differentiations can be interdigitations, desmosomes, tight junctions (zonula occludens), zonula adherens (adherens junctions) and gap junctions.
