mikrovillien

Mikrovillien are microscopic, finger-like projections that extend from the surface of many cells. Their primary function is to significantly increase the surface area of the cell membrane. This amplified surface area is crucial for processes that involve absorption and secretion, as it allows for a greater number of transport proteins and channels to be embedded within the membrane.

These structures are particularly abundant in cells lining the small intestine, where their increased surface area greatly enhances the absorption of nutrients from digested food. In the kidneys, mikrovillien on the cells of the renal tubules facilitate the reabsorption of water and essential solutes back into the bloodstream. They are also found in other epithelial tissues, contributing to their specialized functions.

Mikrovillien are structurally distinct from cilia. While both are cell surface extensions, mikrovillien are shorter, more numerous, and lack the organized microtubule core found in cilia. Instead, they are supported by a core of actin filaments. This structural difference reflects their different roles: mikrovillien are primarily for surface area expansion, whereas cilia are often involved in movement. The presence and density of mikrovillien can vary depending on the cell type and its specific physiological requirements.