The process of removing or eliminating waste products of metabolism and other non-useful materials from a body of a living organism is termed as the Excretion. The entire process of elimination of wastes is controlled by the excretory system. The human excretory system includes specialized organs including a pair of kidneys, ureters, urinary bladder and urethra. These organs are located in the abdominal cavity. The skin, lungs, and liver also function as accessory excretory organs but the urinary system is considered as the main excretory organ which is involved in excretion of nitrogenous waste products, along with water and some mineral salts.