Final answer:
The brushlike border of each villus is composed of microvilli, which are small cylindrical extensions of the plasma membrane of epithelial cells in the small intestine. They greatly increase the surface area of the plasma membrane and enhance absorption.
Step-by-step explanation:
The brushlike border of each villus is composed of microvilli. Microvilli are small cylindrical extensions of the plasma membrane of epithelial cells in the small intestine. They form a mass of bristles known as the brush border, which greatly increases the surface area of the plasma membrane and enhances absorption. These microvilli contain enzymes that help in the digestion of carbohydrates and proteins.