Excretion

Excretion, or elimination, removal of waste material from the body, including the undigested residue of food and the waste products of metabolism. The main organs responsible for elimination in humans are the kidneys and large intestine, which process liquid and solid wastes respectively. Wastes such as water and salt are also eliminated through the skin in the form of sweat, and through the lungs, which expel water vapor and carbon dioxide.