Urinary Bladder
Urinary Bladder Histology
- Adventitia is the outermost layer
- Muscularis comprises the detrusor muscle, a collection of three layers of smooth muscle; the detrusor muscle contracts to expel urine and relaxes during urine storage.
- Submucosa, comprises connective tissues that support the urinary bladder walls, and,
- Mucosa, which, like the mucosa of the ureter, comprises folds of lamina propria and transitional epithelia (not shown, here).
- Mucosal rugae of the internal surface of the urinary bladder facilitate expansion to accommodate urine.
- Openings of the ureters on the posterior/inferior bladder wall and internal urethral orifice form the trigone, is a smooth, triangularly shaped portion of the bladder wall; its shape and smooth surface act as a funnel to direct urine from the openings of the ureters to the urethra.
- Epithelium comprises basal cells, intermediate cells, and, in the apical layer, umbrella cells.
Clinical correlation
- Transitional cell carcinoma is the most common type of bladder cancer; high-grade transitional cell carcinoma can spread through the muscular layer and to nearby organs and lymph nodes.