Inspiration

Inhalation (also known as inspiration) is the movement of air from the external environment, through the airways, and into the alveoli in the lungs.

Inhalation involves contraction of the diaphragm, which results in expansion of the intrapleural space and an increase in negative pressure (Boyle's Law). This negative pressure generates airflow because of the pressure difference between the atmosphere and alveolus. Air enters, inflating the lung through either the nose or the mouth into the pharynx (throat) and trachea before entering the alveoli.