What is transitional epithelium and where is it found?

• A. A stratified epithelium that can stretch and distend; found in the urinary tract (bladder, ureters, part of the urethra).
• B. A simple squamous epithelium used for diffusion; found in alveoli.
• C. A pseudostratified epithelium; lines respiratory tract.
• D. A stratified columnar epithelium; found in the male urethra.

Answer: (A)

Transitional epithelium is a specialized lining that can stretch and distend as the urinary organs fill and empty. It is a stratified type with dome-shaped surface cells when relaxed that flatten as the tissue stretches, allowing the bladder and other parts of the urinary tract to expand without tearing. This tissue lines the urinary tract—the bladder, ureters, and part of the urethra—providing both flexibility and a barrier against urine. Other described epithelia fit different sites (simple squamous for diffusion in alveoli; pseudostratified lining the respiratory tract; stratified columnar in parts of the male urethra), so they don’t match the function and location of transitional epithelium.