Every day the kidneys process about 200 quarts of blood to remove about two quarts of waste products and extra water. The waste and extra water become urine, which flows to the bladder through the ureters. The body's entire blood volume gets filtered through the kidneys about 20 to 25 times a day.
Adults pass about a quart and half of urine each day, depending on the fluids they drink and the foods they eat. The amount of urine produced at night is about half that formed in day. Normal urine is sterile. It contains fluids, salts and waste products, but is free of bacteria, viruses and fungi.
While most people have two kidneys, some people are born with only one. They can live healthy lives with just one kidney. Many people also donate kidneys for transplantation -- and live healthy lives afterwards.
Our kidneys, adrenal glands, bladder and related components filter the blood, remove wastes from the body, regulate blood pressure and the chemical balances of the blood and stimulate the body to produce red blood cells. The images and descriptions in this section are designed to help you understand how these important organs of the body work and how they are situated inside the body.
While organs such as the kidneys and bladder work the same for men as for women, the structure of the urinary track is slightly different. Additionally, the surrounding organs differ. Individual sections are provided for the urinary systems of men and of women.