what are the  two pulmonary ventilation
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. Respiratory muscles are responsible for the changes in the shape of the thoracic cavity that causes the air movements involved in breathing. Inspiration occurs when the chest cavity enlarges. As the thorax enlarges, the lungs expand along with it, and the air rushes into them and down into the alveoli.