What is the function of the brush border in intestinal epithelium?

• A. Increases surface area for absorption and hosts enzymes for digestion
• B. Secretes mucus
• C. Transports nutrients across the membrane
• D. Provides structural support to underlying tissues

Answer: (A)

The brush border is the apical surface of absorptive intestinal cells lined with a dense array of microvilli. This structure massively increases the membrane surface area available for nutrient contact and uptake, making absorption more efficient. In addition, the membranes of these microvilli host brush border enzymes such as lactase, sucrase, maltase, and various peptidases, which perform final digestion right at the membrane so nutrients are ready to be absorbed. Secretion of mucus is carried out by goblet cells, not the brush border. While transporters in this area move nutrients across the enterocyte membrane, the defining role of the brush border is to expand surface area and house these digestive enzymes, enabling efficient digestion and absorption. It does not provide structural support to underlying tissues.