Microvilli are tiny, finger-like projections that extend from the surface of certain cells, primarily epithelial cells. They are essentially microscopic folds in the cell membrane, supported by an internal framework of actin filaments. The main purpose of microvilli is to increase the surface area of the cell, which significantly enhances the efficiency of processes like absorption, secretion, and cellular communication.
Here are some key aspects of microvilli:
- Increased Surface Area: Microvilli dramatically increase the surface area of a cell without significantly increasing its volume. This is crucial for cells involved in absorption, such as those lining the small intestine, where nutrients need to be efficiently taken in.
- Actin Cytoskeleton Support: The core of a microvillus is made up of actin filaments, a type of protein that forms part of the cell's cytoskeleton. This structural support helps maintain the shape and stability of the microvillus.
- Diverse Functions: Microvilli are involved in a wide range of cellular functions, including:
- Absorption: In the intestines, microvilli greatly increase the surface area for nutrient absorption.
- Secretion: Some cells, like those in the kidneys, use microvilli for secretion of substances.
- Cellular Adhesion: Microvilli can play a role in cell-to-cell adhesion and interactions.
- Mechanotransduction: Microvilli can detect mechanical stimuli and transmit signals to the cell's interior.
Examples:
- In the small intestine, microvilli form a structure called the brush border, which increases the surface area for nutrient absorption by several hundredfold.
- Taste buds on the tongue contain microvilli called gustatory hairs, which detect chemicals in food and send signals to the brain about taste.
Microvillus Inclusion Disease: A rare genetic disorder called microvillus inclusion disease affects the development of microvilli in the intestines, leading to severe diarrhea and malabsorption of nutrients.
