Normal urothelium, microscopic
This normal urothelium with an underlying basement membrane is stratified and no more than 5 to 7 cell layers thick, and 2 to 3 cells thick in a distended bladder. The topmost superficial layer is composed of plump (“umbrella”) cells that have microplicae on the luminal border, have tight junctions between them, and can stretch laterally as the urine passes or collects within the lumen.
The bladder urothelium produces a mucoid secretion with natural antibacterial properties. This feature, along with normal complete episodic emptying of the bladder, helps to prevent urinary tract infections. The underlying lamina propria has connective tissue with scattered small vessels.