microviliile

Microvilli are microscopic cellular projections that increase the surface area of cells. They are commonly found on the apical surface of epithelial cells, particularly those involved in absorption, such as in the small intestine and kidney tubules. These finger-like structures are extensions of the cell membrane and are supported by a core of actin filaments, which are cross-linked by proteins like fimbrin and villin. This internal scaffolding helps maintain their shape and rigidity.

The primary function of microvilli is to enhance the efficiency of absorption and secretion. By significantly increasing the surface area available, they allow for a greater rate of nutrient uptake from the lumen of the digestive tract or the filtrate in the kidneys. The dense arrangement of microvilli on the surface of intestinal epithelial cells is often referred to as the brush border. This increased surface area is crucial for the transport of various molecules, including carbohydrates, amino acids, and ions. In some specialized cells, like hair cells in the inner ear, microvilli are modified into stereocilia, which play a role in mechanotransduction.