What structures greatly increase surface area for absorption in the small intestine?

What structures greatly increase surface area for absorption in the small intestine?

• A. Villi and microvilli
• B. Gastric folds
• C. Goblet cells
• D. Mucosal glands

Answer: (A)

In the small intestine, absorption is greatly boosted by a huge increase in surface area created by two levels of projections: villi and microvilli. Villi are tiny finger-like folds of the mucosa that stick into the lumen, and each one contains a rich capillary network and a lacteal. This setup lets nutrients move quickly into blood and lymph as they pass by. On top of that, the surface of each villus is lined with epithelial cells that have even smaller projections called microvilli, forming the brush border. The microvilli multiply the surface area again and host enzymes that finish digestion right at the point of absorption. Gastric folds belong to the stomach, not the small intestine. Goblet cells mainly secrete mucus to protect and lubricate the lining, and mucosal glands also secrete mucus or enzymes rather than expanding surface area. The key idea is that villi plus microvilli dramatically increase the absorptive area, enabling efficient nutrient uptake.

In the small intestine, absorption is greatly boosted by a huge increase in surface area created by two levels of projections: villi and microvilli. Villi are tiny finger-like folds of the mucosa that stick into the lumen, and each one contains a rich capillary network and a lacteal. This setup lets nutrients move quickly into blood and lymph as they pass by. On top of that, the surface of each villus is lined with epithelial cells that have even smaller projections called microvilli, forming the brush border. The microvilli multiply the surface area again and host enzymes that finish digestion right at the point of absorption.

Gastric folds belong to the stomach, not the small intestine. Goblet cells mainly secrete mucus to protect and lubricate the lining, and mucosal glands also secrete mucus or enzymes rather than expanding surface area. The key idea is that villi plus microvilli dramatically increase the absorptive area, enabling efficient nutrient uptake.