Which epithelial type lines the proximal tubules of the kidney, and what feature supports its reabsorptive function?

• A. Simple cuboidal epithelium with a prominent brush border (microvilli)
• B. Stratified squamous epithelium with a keratinized surface
• C. Pseudostratified ciliated columnar epithelium
• D. Simple columnar epithelium without microvilli

Answer: (A)

The proximal tubule is lined by simple cuboidal epithelium, and its key feature that supports reabsorption is the apical brush border formed by numerous microvilli. This greatly expands the surface area available for transport proteins and channels, enabling efficient reclaiming of solutes like glucose, amino acids, bicarbonate, salts, and a large amount of water from the filtrate. The cell layout—tall enough to house essential organelles and tightly connected as a single layer—coupled with abundant mitochondria to fuel active transport, underpins this high absorptive capacity. Other epithelial types listed would not provide the same extensive surface area or the appropriate transport machinery needed for bulk reabsorption.