What is Transitional Epithelium?
Transitional epithelium, also known as
urothelium, is a type of stratified epithelium characterized by its ability to stretch and change shape. It is primarily found lining the urinary tract, including the
urinary bladder,
ureters, and part of the
urethra. This adaptability allows these organs to accommodate varying volumes of fluid.
Structure of Transitional Epithelium
Transitional epithelium consists of multiple layers of cells. The
basal cells are typically cuboidal or columnar, while the intermediate cells are polygonal, and the surface cells, known as umbrella cells, are large and dome-shaped. When the bladder is empty, these surface cells appear more cuboidal, but when stretched, they become flatter and more squamous-like.
Functions of Transitional Epithelium
The primary function of transitional epithelium is to provide a barrier that can withstand the toxic effects of urine while allowing for the distensibility of the urinary organs. It also helps to maintain a waterproof barrier to prevent the absorption of urine back into the bloodstream. Histological Staining and Identification
Transitional epithelium can be identified using
histological staining techniques such as Hematoxylin and Eosin (H&E). The unique structure and variability in cell shape depending on the state of distension make it distinguishable from other types of epithelium. The presence of large, dome-shaped umbrella cells is a key identifying feature.
Clinical Significance
Transitional epithelium is significant in diagnosing various
pathological conditions. Conditions such as bladder cancer, interstitial cystitis, and urinary tract infections can affect the structure and function of this epithelium.
Biopsies and histological examinations are often performed to diagnose and monitor these conditions.
Common Questions
Why is it called transitional epithelium?
It is called transitional because the cells can transition between different shapes and layers depending on the degree of distension in the urinary organs. How does transitional epithelium differ from other types of epithelium?
Unlike simple or stratified epithelium, transitional epithelium is uniquely adapted to stretch and recoil. It has a unique arrangement of cells that allows it to change shape without losing its integrity.
What changes occur in transitional epithelium when the bladder is full?
When the bladder is full, the transitional epithelium stretches, and the surface cells become flatter, resembling squamous cells. This allows the bladder to expand and hold more urine.
What are umbrella cells?
Umbrella cells are the large, dome-shaped cells on the surface layer of transitional epithelium. They play a crucial role in providing a protective barrier and allowing the epithelium to stretch.
