Pulmonary Ventilation a.k.a. Breathing

There are two phases in breathing: inspiration (inhalation) and expiration (exhalation).

When we inhale, our chest expands, decreasing the intrapulmonary pressure, which creates a vacuum to allow air to enter the lungs.

When exhalaing, our chest depresses, increasing the intrapulmonary pressure and causing air to flow out of the lungs.

A comparison of our rib cage during inspiration and expiration is displayed in Figure 13.7 a & b (below).