Activity 5B 5 The blood then takes the oxygen to the rest of the body cells while carbon dioxide leaves the body wben you exhale. 3 In the lungs, air enters through bronchial tube to bronchioles and to the alveoli. 4 When air goes into the air sac, oxygen goes to the wall of the air sacs then through the walls of the blood vessels and to the blood. 1 As you inhale, air enters the nose or mouth. It is then filtered, warmed and humidified in the different parts of the upper respiratory tract. 2 The air passes through the pharynx, larynx, then into the trachea and into the lungs,