What are the fingerlike projections lining the walls of the small intestine called?

• A. Villi
• B. Microvilli
• C. Crypts
• D. Cilia

Answer: (A)

Fingerlike projections lining the walls of the small intestine are called villi. These structures dramatically increase the surface area available for nutrient absorption, which is essential for efficiently taking in digested food. Each villus contains a network of capillaries and a lacteal to transport absorbed nutrients—carbohydrates and amino acids into the bloodstream, and fats into the lymphatic system. The surface of the villi is covered with even smaller projections called microvilli, which form the brush border and provide even more surface area for enzyme action and absorption. The crypts are glands located at the base of the villi, not projections lining the walls, and cilia are hairlike structures used for movement in other tissues.