The lungs are the primary organs of the respiratory system, but the other organs which enable the air to get to and from the lungs are also part of the system. These include the air passages; the nose, nasal cavities, mouth, pharynx, larynx , trachea and bronchus. The respiratory system provides for gas exchange supplying oxygen to the blood and removing CO2 from the blood.

Air enters the body through the nose and mouth, it flows down through the pharynx, larynx, trachea and bronchus into the lungs. Each bronchi break down into bronchioles and eventually into millions of tiny sacs called alveoli.

At this point oxygen passes out of the air into the blood and carbon dioxide passes out of the blood into the air in the alveoli.