In the small intestine, where does most nutrient absorption occur and what is the role of microvilli?

• A. Most absorption occurs in the duodenum; microvilli decrease surface area.
• B. Most absorption occurs in the jejunum and ileum; microvilli increase surface area.
• C. Absorption occurs only in colon; microvilli are the same.
• D. Most absorption occurs in the stomach; microvilli are not important.

Answer: (B)

The most nutrient absorption happens mainly in the jejunum and ileum, where the lining has extensive folds with villi and microvilli to maximize contact with digested food. Microvilli are tiny projections on enterocytes that multiply the surface area available for nutrient uptake and host brush-border enzymes that finish digestion at the surface. The duodenum does some absorption but not the bulk, while the stomach and colon have different primary roles (stomach for digestion/storage; colon for water and electrolyte absorption). So, the combination of absorption sites and the surface-area-boosting role of microvilli makes this option the best choice.