Final answer:
The function of transitional epithelium is to accommodate changes in the volume of the bladder as it fills and empties, forming an expandable lining that protects underlying tissues.
Step-by-step explanation:
The function of transitional epithelium is primarily associated with the urinary system, particularly in the bladder and ureter. This form of stratified epithelium is unique because it can change shape in response to the physical stretching of the bladder as it fills with urine. When the bladder is empty, the transitional epithelium is convoluted, and the cells appear cuboidal with umbrella-shaped apical surfaces. As the bladder becomes distended with urine, the epithelium stretches, causing the cells to transition from a cuboidal to a more flattened, squamous shape. This allows the bladder to hold larger volumes of urine without tearing or damage to the epithelial lining. The unfolding and expanding of these cells contribute to the bladder's ability to expand and contract while providing a protective and selectively permeable barrier. In summary, the transitional epithelium's main role is to accommodate changes in volume within the urinary bladder, acting as a barrier that expands and contracts while ensuring the protection of underlying tissues from urine's corrosive nature.