What primarily occurs during exhalation?

During exhalation, the diaphragm relaxes, which is a critical part of the respiratory process. When the diaphragm, a dome-shaped muscle located at the base of the thoracic cavity, relaxes, it moves upward into its original position. This action decreases the volume of the thoracic cavity. According to Boyle's Law, as the volume of a space decreases, the pressure within that space increases. As a result, the increased pressure in the thoracic cavity forces air out of the lungs and into the atmosphere.

This process is essential for respiratory function as it facilitates the removal of carbon dioxide-rich air from the lungs, ensuring that gas exchange can continue efficiently. Understanding this mechanism is key to grasping how the respiratory system maintains homeostasis by regulating the levels of oxygen and carbon dioxide in the blood.