The urinary system - also known as the renal system - produces, stores and elimiates urine, the fluid waste excreted by the kidneys. The system works with the lungs, skin and intestines to maintain the balance of chemicals and water in the body.
The kidneys are the primary organs of the urinary system. They remove urea - a waste product formed by the breakdown of proteins - from the blood through filtering units called nephrons.
A normal, healthy bladder can hold up to 16 ounces (almost half a liter) of urine comfortably for 2 to 5 hours.