the purpose of the respiratory system is to bring oxygen to the lungs and remove unnecessary gases. Whether breathing through mouths, gills or the skin, there is an exchange of gases in the body. In mammals, air is breathed passing through the
back of the nose and then it flows into two tubes that branch off from the windpipe in the throat. When you breathe out, carbon dioxide is released. However, plants breathe in carbon dioxide. Birds have a different respiratory system and use air sacs. Two less important functions of the respiratory system are swallowing food and smelling.