Explain how gaseous exchange occurs in the lungs

Oxygen enters the nose/mouth along the trachea, bronchi, bronchioles and finally into the alveoli.The exchange of gases occurs between the alveoli and blood in the capillaries that supply the lungs. Capillaries cover 70% of the outside of alveoli, providing a large surface area for gases to diffuse across.Oxygen moves into the capillaries and CO2 moves out.