Which features maximize surface area for absorption in the small intestine?

• A. Goblet cells only
• B. Plica circularis (circular folds), villi, and microvilli
• C. Crypts of Lieberkühn only
• D. Submucosal glands

Answer: (B)

The main idea is that the small intestine increases its absorptive surface through a series of structural enlargements: circular folds, villi, and microvilli. The circular folds (plica circularis) slow the passage of chyme and create more contact with the mucosa, effectively increasing the area available for absorption. The villi are finger-like projections that extend into the lumen, themselves covered with enterocytes. Each enterocyte has microvilli on its surface, forming the brush border; these microvilli dramatically multiply the surface area and bring digestive enzymes right to where nutrients are absorbed.

Goblet cells mainly secrete mucus to protect and lubricate the lining, not to boost surface area. The crypts of Lieberkühn are glands at the bases of the villi that renew epithelium and contribute to secretion, but they don’t significantly increase the absorptive surface. Submucosal glands also secrete mucus to protect the mucosa, not to enlarge absorption surface.

So, the features that maximize surface area for absorption are the circular folds, villi, and microvilli.