The bladder is a balloon-shaped muscle that stores urine. It is part of the urinary tract, along with the kidneys, ureters, and the urethra.

The kidneys filter waste products and water from the blood to form urine. The urine moves from the kidneys through tubes called ureters to the bladder, where the urine is stored. From the bladder, urine leaves the body through another thin tube, the urethra.