The function of the villi in the alimentary canal is to

Step 1: Analyze the question The question asks about the function of villi in the alimentary canal. Villi are tiny finger-like projections found in the lining of the small intestine (especially the ileum).

Step 2: Explain the concept After food is digested in the small intestine, the digested nutrients (glucose, amino acids, fatty acids, glycerol, vitamins) must pass into the blood and lymph. The faster and more efficiently this happens, the better. Villi help in these ways:

• They greatly increase the surface area of the intestinal wall.
• They have thin walls (one cell thick) for quick diffusion.
• They have a rich blood supply (capillaries) to carry away absorbed food.
• They have a lacteal (a lymph vessel) to absorb fatty acids and glycerol.

Step 3: Check each option

• A. Secrete gastric juice: This is done by the gastric glands in the stomach wall, not by villi. ❌
• B. Curdle milk: This is done by rennin (in infants) in the stomach. ❌
• C. Emulsify fat: This is done by bile salts from the liver (stored in the gall bladder). ❌
• D. Increase the surface area for absorption: This is the correct function of villi. ✅

Answer: D

Tip: Link the word to its job. Villi = absorption in the small intestine. Whenever you see "surface area" in a biology question, think of structures designed for absorption or exchange, such as villi, root hairs, and alveoli. Also remember that gastric juice belongs to the stomach, and emulsification belongs to bile.