What happens to the diaphragm and external intercostal muscles during exhalation?

During exhalation, the diaphragm and external intercostal muscles both relax. This is a key part of the respiratory cycle.

When the diaphragm relaxes, it returns to its dome-shaped position, decreasing the volume of the thoracic cavity. Simultaneously, the external intercostal muscles, which assist in expanding the thoracic cavity during inhalation, also relax. This relaxation leads to a decrease in the space available for the lungs, resulting in increased pressure within the thoracic cavity compared to the atmospheric pressure. Consequently, air is expelled from the lungs as it moves from an area of higher pressure to an area of lower pressure outside the body.

Understanding the mechanics of breathing is crucial, as the actions of these muscles directly impact lung volume and air flow. Therefore, during exhalation, the coordinated relaxation of the diaphragm and external intercostal muscles is essential for efficiently expelling air from the lungs.