Flow chart

• 1. The air is drawn in by the nose and mouth and is warmed in these structures
• 2. Air moves through the pharynx and past the larynx
• 3. Air moves down the trachea
• 4. Trachea divides into two bronchial tubes
• 5. Bronchus divides into small bronchioles and eventually end in small air sacs called alveoli
• 6. Alveoli have thin walls and are convered in capillaries carrying blood. Oxygen passes through the thin walls of the alveoli to the blood, and CO2 moves in the opposite direction.
• 7. The air in the lungs which in now high in CO2 is exhaled.