The respiratory system's main job is to replace waste gases with oxygen and fresh air. The respiratory system consists of the lungs, trachea, nose, bronchial tubes, alveoli, and the diaphragm. The job of the nose is to inhale and exhale the air. It's a hole in the body where air can be exchanged. The mouth can do the same thing but its main function relates to the digestive system. The job of the lungs is to store the oxygen and release CO² through the trachea, which is a tube from the nose the leads to the bronchial tubes. The bronchial tubes are in the lungs and at their tips are alveoli. Alveoli are little round endings that have capillaries on them. Capillaries are blood vessels where arteries and veins meet. Those carry red blood cells, which carry oxygen.