Which cells are the absorptive cells lining the intestinal villi with microvilli?

• A. Enterocytes are absorptive cells lining the villi with microvilli.
• B. Enterocytes line alveolar walls.
• C. Enterocytes secrete mucus.
• D. Enterocytes do not exist.

Answer: (A)

Absorptive function in the small intestine is carried out by enterocytes, the tall columnar cells that line the villi. Their apical surface is covered with a dense brush border of microvilli, which dramatically increases surface area for nutrient uptake. The microvilli host brush-border enzymes that complete the digestion of carbohydrates and peptides, and transporters on the apical membrane move sugars and amino acids into the cell for entry into the bloodstream. Goblet cells secrete mucus and are scattered among enterocytes, not the primary absorptive unit. The lining of alveolar walls belongs to lung pneumocytes, not intestinal absorptive cells. Thus, enterocytes are the cells described.