The kidneys are the filtering devices of blood. The kidneys remove waste products from metabolism such as urea, uric acid, and creatinine by producing and secreting urine. Urine may also contain sulfate and phenol waste and excess sodium, potassium, and chloride ions. The kidneys help maintain homeostasis by regulating the concentration and volume of body fluids. For example, the amount of H+ and HCO3 - secreted by the kidneys controls the body's pH.
