Which cells are found in transitional epithelium that contribute to its stretchability?

• A. Umbrella cells
• B. Goblet cells
• C. Fibroblasts
• D. Chondrocytes

Answer: (A)

Transitional epithelium relies on specialized surface cells called umbrella cells to provide stretchability. These large, dome-shaped cells sit at the luminal surface and can flatten and unfold as the bladder distends, allowing the epithelium to stretch without tearing. Their apical membrane is reinforced with uroplakin plaques and tight junctions, which helps maintain a barrier while the tissue expands. Goblet cells secrete mucus and are not characteristic of transitional epithelium; fibroblasts are connective-tissue cells; chondrocytes are cartilage cells—none of these contribute to the stretchiness of the urothelium the way umbrella cells do.