What are microvilli?

Microvilli are small, finger-like projections that extend from the surface of epithelial cells, particularly in the intestines and kidneys. Their primary function is to increase the surface area of the plasma membrane, which enhances the cell's ability to absorb nutrients and other substances. This is especially important in organs involved in absorption, such as the small intestine, where microvilli form a structure known as the brush border. This adaptation plays a crucial role in maximizing the efficiency of nutrient uptake from digested food.

The other options do not accurately describe microvilli. Large projections in the stomach refer to different anatomical features and do not contribute specifically to the absorption process. Structures involved in food breakdown in the mouth pertain to different components of digestion, such as teeth and saliva, rather than microvilli. Tissue layers in the small intestine represent the different types of cells and tissues that make up the intestinal structure but do not specifically refer to the function or structure of microvilli.