Mikrovillat

Mikrovillat are microscopic, finger-like projections that extend from the surface of certain cells. Their primary function is to significantly increase the surface area available for absorption or secretion. These structures are particularly abundant in cells lining the small intestine, where their vast surface area is crucial for efficient absorption of nutrients from digested food. Similarly, they are found in kidney tubules, aiding in the reabsorption of water and solutes.

Structurally, each microvillus is supported by a core of actin filaments, which are linked together by myosin proteins. This internal scaffolding allows the microvilli to maintain their shape and also enables some degree of movement, which can further enhance their absorptive efficiency. The outer membrane of a microvillus is continuous with the cell membrane and is often covered with glycoproteins.

The increased surface area provided by microvilli can be several hundred to several thousand times that of a smooth cell surface. This amplification is a key adaptation for cells involved in transport processes. In the intestine, the collection of microvilli on the apical surface of epithelial cells forms a brush border, a characteristic feature visible under a microscope. Their presence is vital for many physiological functions, including nutrient uptake, waste removal, and sensory reception in some contexts.