Pulmonary Ventilation or breathing has two phases. Inspiration or inhalation moves air into the lungs, and expiration or exhalation moves are out of the lungs. The lungs are enclosed within the thoracic cavity. Thus changes in the shape and size of the thoracic cavity result in changes in the air pressure within that cavity & in the lungs. This difference in air pressure causes the movement of air into and out of the lungs. Air moves from an area where pressure is high to an area where pressure is lower. …
