Transitional epithelium is named for its ability to do what?

• A. It has multiple cell layers that can change shape from cuboidal to squamous during distension, enabling stretch and recoil.
• B. It is a single layer of tall columnar cells with apical microvilli.
• C. It remains cuboidal regardless of distension.
• D. It forms keratinized surface in certain regions.

Answer: (A)

Transitional epithelium is defined by its ability to stretch by changing the shape of its cells as the organ fills and empties. In a relaxed state, it is multilayered with cells that are closer to cuboidal in the deeper layers and dome-shaped at the surface. When the tissue distends, the surface cells flatten and spread out, so the epithelium becomes thinner and more squamous-like. This shape change lets the urinary bladder and other parts of the urinary tract expand to hold urine and then recoil back afterward, without tearing or losing barrier function. It’s not a simple single-layer epithelium, and it isn’t keratinized like skin, so those options don’t describe the unique distensible, transitional nature.