Final answer:
Microvilli are small, cylindrical extensions of the plasma membrane found on epithelial cells in the small intestine, which greatly increase the cell's surface area and optimize the absorption of nutrients.
Step-by-step explanation:
Microvilli are abundant on epithelial cells that specialize in absorption, specifically within the small intestine. They serve to increase surface area for absorption, which enhances the uptake of nutrients like carbohydrates, proteins, bile salts, and vitamin B12. These cellular projections contain enzymes that assist in completing the digestion process. Each microvillus contains a core of actin microfilaments, and a dense cluster of these microvilli forms the brush border. The small intestine's interior surface is lined with cells that possess microvilli, and this arrangement allows for an efficient absorption system due to the substantial increase in surface area.
This exemplifies the principle where the form of a biological structure is integrally related to its function. By extending the plasma membrane in such a way, the cells can absorb more from the chyme, which is the semiliquid mass of partly digested food.The microvilli contain enzymes that finish digesting carbohydrates and proteins, enhancing absorption.