Why are microvilli important

Skip to main content Skip to table of contents. This service is more advanced with JavaScript available. Contents Search. How to cite. Definition Microvilli are finger-shaped plasma membrane protrusions that are found at the surface of a large variety of cell types but are most numerous and elaborated on simple epithelial, for example intestinal mucosa and the epithelium of the kidney proximal tubule. This is a preview of subscription content, log in to check access. Filament polarity and membrane attachment in the microvilli of intestinal epithelial cells.

J Cell Biol — Google Scholar. Bretscher A, Weber K Localization of actin and microfilament-associated proteins in the microvilli and terminal web of the intestinal brush border by immunofluorescence microscopy. Nature —64 PubMed Google Scholar. Bevilacqua MP, Stengelin S, Gimbrone MA Jr et al Endothelial leukocyte adhesion molecule 1: an inducible receptor for neutrophils related to complement regulatory proteins and lectins. E xchange of substances between cavities or external environment and tissues is one the main function of epithelia, such as intestine and kidney epithelia.

It is mostly done at the apical free surface of the epithelial cells, where most molecular transporter, ion pumps are located, and endocytic processes happen. The more cell surface the more space to accommodate the molecular machinery for the exchange. Microvilli are spine-like protrusions that increase enormously the plasma membrane surface and therefore the membrane protein content. This particularly important in those absorptive and secretory cells of epithelia.

Microvilli may increase the cell surface up to times compared with a flat membrane. Enterocyte microvilli bear many enzymes, which are not involved in molecular exchange, but in digestion. M icrovilli may influence transduction molecular pathways. Their membranes work as relatively isolated domains with a distinct set of molecules, like glucose transporters, ion pumps and receptors.

The length of microvilli is well suited for performing local transduction of the molecular pathways independently of the cytosol. In addition, the actin filaments and structural proteins scaffold form a dense network of molecules that somehow filters or controls the molecules coming or quitting the interior of each microvellosity. This scaffold also may work as a temporal storage for calcium.

T he high density of microvilli makes a physical barrier that protects against pathogens. This is important for intestine epithelium. In addition, the large amount of membrane stored in microvilli is a reservoir that can withstand hypertonic insults and prevent the breakage of the plasma membrane. S tereocilia are specialized microvillosities performing sensory functions. Despite the name stereocilium, they are actually modified microvillosities transformed into sensory structures, and some authors propose the name estereomicrovellosity instead.

They can be found in the epididymis epithelium, and in the inner ear, working as mechanoreceptors that sense the surrounding fluid movement. Sterocilia of the mammal inner ear are found as part of the Corti's organ. The sound waves of the air are transformed in fluid waves in the ear, which stereocilia sense and transform into electrical signals that travels via auditory nerve to the brain.

Stereocilia are like antennas that receive external signals, which are transduced in electrical information. S ome microvellosities are specialized in sensing light. Photorreceptors are light sensory cells found in visual organs like the retina. The cellular sensory structures are actually modified cilia or microvellosities. Photoreceptors bearing modified microvellosities for light detection can be found in invertebrates visual structures.

Those photoreceptors contain microvellosities arranged in the so-called rhabdomeres. Each microvellosity contains visual pigments that can respond to low light intensities and are efficient at high light intensities. Microvellosities organize forming the so-called rhabdomere, and the transduction molecular pathway make microvillosity based light response more sensible than cilium light sensory systems of vertebrates. A large number of extracellular vesicles are proposed to be released from microvilli.

The tips of enterocyte microvilli are able to release vesicles to the surrounding environment. The connection between plasma membrane and actin-myosin network may help to produce these vesicles by dragging membrane toward the distal part of each microvellosity, where small portions of membrane are transformed in vesicles.

These extracellular vesicles contain enzymes and are enriched in alkaline phosphatase. Molecular model of the microvillar cytoskeleton and organization of the brush border. PLoS One. Shaping the intestinal brush border. J Cell Biol. Phototransduction and the evolution of photoreceptors. Curr Biol. Lange K. Fundamental role of microvilli in the main functions of differentiated cells: Outline of an universal regulating and signaling system at the cell periphery. J Cell Physiol. The enterocyte microvillus is a vesicle-generating organelle.

Structure, regulation, and functional diversity of microvilli on the apical domain of epithelial cells. Annual review of cell and development biology.