Transitional epithelium, also known as urothelium, is a specialized type of epithelium that can stretch and recoil without damage. It consists of multiple layers of cells that change shape depending on the degree of distension in the organ it lines.
Anatomy
- Structure:
- In the relaxed state, the cells in the superficial layer appear dome-shaped (sometimes called “umbrella cells”).
- When stretched, the cells flatten, resembling squamous cells.
- Cell Layers:
- Basal layer: Cuboidal cells.
- Intermediate layer: Columnar or polygonal cells.
- Apical layer: Dome-shaped cells that flatten during stretching.
Location
Transitional epithelium is found exclusively in the urinary system, where organs need to accommodate varying volumes of liquid. Major locations include:
- Renal pelvis.
- Ureters.
- Urinary bladder.
- Proximal urethra.
Function
- Stretchability: Allows organs to expand and contract without tearing.
- Barrier: Provides a protective lining, preventing the leakage of urine and protecting underlying tissues from its toxic components.
Clinical significance
- Urinary Tract Infections (UTIs): Recurrent infections can damage the transitional epithelium, leading to discomfort and potential complications.
- Bladder Cancer: Transitional cell carcinoma arises from the transitional epithelium and is a common cancer affecting the bladder.
- Obstruction Effects: Chronic obstruction (e.g., kidney stones) can cause changes in the transitional epithelium, potentially leading to complications like hydronephrosis.
