The major function of the respiratory system is the exchange of oxygen and carbon dioxide between the blood and the atmosphere. In addition to this gas exchange, the respiratory system also regulates blood pH.

The organs of this system include the nose, pharynx, larynx, trachea, bronchial tree, and the lungs. Each of these structures has a role in ventilation (bringing air in and out of the body) and external respiration (the gas exchange of oxygen and carbon dioxide). Understanding this system is important in assisting with patients and instructing them in the use of an inhaler.