What happens during exhalation?

During exhalation, the process primarily involves the relaxation of the diaphragm and the intercostal muscles. As these muscles relax, the diaphragm moves upward, and the rib cage descends. This reduction in volume within the thoracic cavity causes the lung volume to decrease, which leads to increased pressure within the lungs. Consequently, air is expelled from the lungs as they recoil due to their elastic properties.

This means that the correct answer describes the physiological principle of lung recoil, which is vital for the expulsion of air during exhalation. When the muscles involved in breathing relax, the elastic fibers in the lung tissue facilitate this recoil, pushing air back out into the environment. Understanding this mechanism highlights the relationship between muscle activity, lung pressure, and airflow.