What structural feature enables distension in transitional epithelium?

• A. Dome-shaped umbrella cells that flatten during distension.
• B. Non-distensible stratified layers.
• C. Keratinized surface cells.
• D. Absence of basement membrane.

Answer: (B)

The ability of transitional epithelium to distend comes from surface umbrella cells that are dome-shaped when the bladder is empty and flatten as it fills. This flattening, combined with a flexible apical membrane and strong cell–cell junctions, allows the tissue to stretch without tearing while preserving a barrier. A non-distensible layered arrangement would prevent expansion, keratinized surface cells are not a feature of this epithelium, and the basement membrane is present, not absent.