Illustration of a male human urinary bladder (frontal view of a cross-section). The urinary bladder is a muscular hollow organ of the urinary system. It collects the secondary urine that is constantly produces by the kidneys. It has a capacity of up to 1000 ml. This capacity, also called urinary continence, makes the body independent of the continual urine production of the kidneys for a period of time. On the inside the bladder is lined with urothelium, that protects and produces uroplakin. It ends in the urethra. The men`s urethra also transports the sperm and at its bottom, the prostata is attached.