The urinary tract is composed of four parts:
- the kidneys which produce the urine by removing water from the blood
- the ureters which are tubes connecting the kidneys to the bladder
- the bladder which stores the urine in the body
- the urethra, the tube which carries the urine out of the bladder.
The bladder is a hollow balloon-shaped organ. Its walls are made of muscle. The walls of the urethra are surrounded by muscles which squeeze to keep the urethra closed and hold the urine in.