Transitional epithelium

A specialized type of tissue that stretches and changes shape to accommodate variations in volume.

Transitional epithelium is a unique type of tissue that lines certain organs, such as the bladder, allowing for significant expansion and contraction without losing its integrity. This epithelial layer is characterized by its ability to transition between a relaxed, contracted state and a stretched state, showcasing multiple layers of cells that can appear balloon-like when the organ is distended.

Terminologia Anatomica

epithelium-transitional

System

Urinary system

Function

The primary function of transitional epithelium is to provide a flexible barrier that can withstand the fluctuations in volume typically seen in organs like the urinary bladder. As the bladder fills with urine, the transitional epithelial cells expand, allowing the bladder to increase in size without damage. When the bladder empties, the cells revert to their original, thinner state. This unique adaptability enables the tissue to serve both protective and functional roles, safeguarding underlying tissues from exposure to potentially harmful substances in urine, while also facilitating the storage and release of urine.

Location

Transitional epithelium is primarily located within the urinary system. It lines the inner surface of the urinary bladder, the ureters, and to a lesser extent, the part of the urethra closest to the bladder. The positioning of this tissue is crucial as it directly facilitates the organ's ability to expand when filled with urine and contract when empty. While the bladder can hold approximately 400 to 600 milliliters of urine, the transitional epithelium’s strategic location ensures that the organs can accommodate varying amounts successfully.

Did You Know?

Transitional epithelium can appear to have multiple layers when the bladder is empty but can flatten significantly when the bladder is full.
Unlike other types of epithelial tissue, transitional epithelium can contain binucleate (two nuclei) cells.
This type of epithelium is most commonly found in organs that have variable volumes, demonstrating its evolutionary adaptation for purpose.