Role of Liver in ExcretionThe largest gland in out body is the liver. Its secretions include bilirubi, biliverdin, cholesterol, degraded steroid hormones, vitamins and drugs. Most of these secretions are passed out along with the digested waste material. Role of Lungs in ExcretionThe Lungs is the main respiratory organ. It excretes the waste gas CO₂ by exhalation and also small quantities of water.Role of Skin in ExcretionThe skin is the largest receptor organ covering the entire body. It contains the sweat and sebaceous gland. The secretions of these glands are sent out of the body. The sweat secreted by the sweat gland contains NaCl, small amount of urea, lactic acid etc. These waste materials are excreted along with the sweat. The sebaceous glands excrete substance like sterols, hydrocarbons and waxes through sebum.