What is the primary function of microvilli in absorptive epithelia?

• A. Increase surface area for absorption and secretion
• B. Propel mucus along the surface
• C. Provide structural support
• D. Produce mucus

Answer: (A)

Microvilli expand the apical surface of absorptive epithelial cells, dramatically increasing the area available for interactions with luminal contents. That larger surface supports more membrane transporters and brush border enzymes, which makes nutrient uptake and local digestion more efficient. The core of each microvillus is an actin filament bundle that provides rigidity, so they stay as tiny projections rather than moving, unlike cilia that propel mucus. So the primary idea is that microvilli maximize contact with what’s in the lumen to boost absorption (and the surface enzymes help complete digestion at the cell surface). Mucus production is done by goblet cells, and propulsion of mucus is a job of motile cilia, not microvilli.