What occurs to the diaphragm during the process of expiration?

During the process of expiration, the diaphragm relaxes and moves up. This occurs as the respiratory muscles, including the diaphragm, decrease their activity. As the diaphragm relaxes, it returns to its original dome-shaped position, which reduces the volume of the thoracic cavity. This decrease in volume creates a higher pressure inside the thoracic cavity compared to the atmospheric pressure outside the body, leading to the expulsion of air from the lungs.

Understanding that the diaphragm's relaxation is a key aspect of normal breathing mechanics is crucial. Breathing involves both the contraction during inhalation, where the diaphragm moves down and increases the thoracic volume, and the relaxation during expiration, where it moves back up to help push air out. This coordination between contraction and relaxation is essential for efficient respiratory function.