We eat various things daily which forms waste materials. Excretory system helps to remove wastes and toxic materials from the body.
The waste materials must come out of our body otherwise they will cause us diseases. Our excretory system does this important work.
The organs involved in this system are kidneys, skin, lungs and the large intestine. Kidneys filter the urine and throw it out. Skin lets out sweat and throws out salt. Lungs send out carbon-di-oxide and other impurities out of our body while breathing out. The large intestine throws out solid waste through the anus.
Thus, kidneys, skin and lungs constitute our excretory system. This keeps the body clean and healthy.