Breathing is a complex process that happens several times within just a minute. Although involuntary, breathing is vital for a person to live. Inhaling and exhaling is essentially changing the air pressure inside the body to take in and remove air.
When a person inhales, the diaphragm and the muscles between the ribs contract and expand the chest cavity. When the chest cavity expands, the pressure in the chest is lowered to a level below that of the air pressure outside. When this happens, air flows in through the airways from a high pressure to low pressure and inflates the lungs.
When a person exhales, the diaphragm and muscles between the ribs relax and make the chest cavity smaller. The decrease in the volume of the chest cavity increases the pressure to a level that is higher than the air pressure outside. The air from the lungs then flows out of the airways to the outside air.
Take another breath
The cycle of changing the air pressure in a person's body repeats with each breath he takes. Breathing is essential for life, and the air that is breathed in regulates several processes within a person's body.