Accessory Excretory Structures Balance contd/.


Urinary Bladder

The urinary bladder is a hollow, muscular organ that collects urine from the ureters and stores it until it is time to excrete it. Usually accumulates 300 to 400ml of urine before it empties though it can hold up to twice as much.

The urinary bladder is composed of three main layers


It is lined with transitional epithelium, which allows the bladder to stretch.


Middle layer, the tunica muscularis, consists of three layers of smooth muscle - an inner and outer layer of longitudinal and a middle circular layer. The three layers are known as the detrusor muscle.


Outermost layer, the adventitia. It is derived from the peritoneum and covers only ht eupper and lateral surfaces of the blader. Being moist it lubricates and eliminates friction when the bladder is full.