* Air distribution: This involves the movement of air through the airways (nose, pharynx, trachea, bronchi, bronchioles) to the alveoli, where gas exchange occurs.

* Gas exchange: This is the process of transferring oxygen from the inhaled air to the blood and carbon dioxide from the blood to the exhaled air. This occurs in the alveoli, tiny air sacs in the lungs where the blood vessels are very close to the air.