What is one notable characteristic of transitional epithelium?

Transitional epithelium is uniquely characterized by its ability to stretch and accommodate fluctuations in the volume of liquid within an organ. This type of epithelium, primarily found lining the urinary bladder, ureters, and parts of the urethra, is designed to provide a barrier while also allowing for significant expansion and contraction as these organs fill with and empty urine.

When the bladder is empty, the cells appear more cuboidal and are packed closely together, but as the bladder fills with urine, the cells become flattened to allow for expansion. This dynamic adaptability is essential for its function in the urinary system.

In contrast, a single layer of cells would describe simple epithelium, and a densely packed arrangement may refer to other types of epithelial tissues like stratified epithelium. Similarly, the notion of consisting entirely of squamous cells pertains to a specific type of epithelium such as simple squamous or stratified squamous epithelium, which do not have the ability to stretch as transitional epithelium does. Thus, the defining feature of transitional epithelium lies in its capacity to contract and expand in response to the volume of urine it encounters.