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Various systems are responsible for the elimination of wastes. The digestive system eliminates wastes which are associated with solid forms of nutrients and wastes derived from edible content. Carbon dioxide is eliminated from the body via the respiratory system. The integumentary system is responsible for the removal of excessive metabolic heat, nitrogenous wastes, salt, and excess water.

http://www.medical-look.com/human_anatomy/systems/Urinary_system.html