The organ system that filters blood and removes nitrogenous wastes from the body in the form of urea or uric acid. In humans, the two kidneys are the vital organs of blood filtration. In annelids, nephridia fill the filtering role; Malpighian tubules do the same in arthropods. In humans, other important structures of the system are the ureters, the urinary bladder, and the urethra.

The part of the lacrimal system which provides for drainage of the tear film.

One of eleven major body systems in animals; regulates the volume and molecular and ionic constitution of internal body þuids and eliminates metabolic waste products from the internal environment.