What is the bladder?

The urinary bladder, or the bladder, is a hollow organ present in the pelvis. Most of it lies behind the pubic bone of the pelvis but when full it can extend up into the lower part of the abdomen. Its primary function is to store urine that drains into it from the kidney through tube-like structures called the ureters. The ureters from both the kidneys open into the urinary bladder. The bladder forms a low-pressure reservoir which gradually stretches out as urine fills into it. In males, the prostate gland is located adjacent to the base of the bladder where urethra joins the bladder. From time to time, the muscular wall of the bladder contracts to expel urine through the urinary passage (urethra) into the outside world.