Breathing is a physical process that involves intercoastal muscles which lie between the ribs and the diaphragm and help in breathing.
It involves 2 actions that are inhalation and exhalation.
Mechanism of breathing:
Inhaling:
During inhaling, the intercostal muscles contract, the ribs are pushed upward and outward, and the diaphragm contracts and moves downward.
And this upward and outward movement of the ribs and the descending movement of the diaphragm add to the space in the chest cavity.
It increases the volume of the air-tight chest cavity and creates pressure inside the lungs.
Air rushes from the outside through the trachea to the air sacs and alveoli.
Exhaling:
During exhaling, the intercostal muscles relax, and simultaneously two movements take place that is the ribs move downward and inward, and the diaphragm relaxes and moves upward to take up its original position.
This movement reduces the space in the chest cavity and the air rushes out of the lungs.