Breathing

In humans, the process of breathing, the inhalation and exhalation of air requires coordination between the lungs, the chest wall, and the diaphragm, a skeletal muscle that makes up the floor of the thoracic cavity.

During inhalation the diaphragm and the intercostal muscles connected to the ribcage contract, increasing the volume of the thoracic cavity, thereby inversely decreasing the pressure relative to the outside.

As a result of the drop in pressure, air, now moving from high to low pressure is pulled into the respiratory passageways and into the alveoli of the lungs.

When the diaphragm and rib muscles relax, the volume decreases which increases the pressure pushing air out of the lungs and body.

Thus, breathing is a rapid process of inflating and deflating the lungs with every breath.