What is the main purpose of the diaphragm in the respiratory process?

• A. To filter air entering the lungs
• B. To transport oxygen to the blood
• C. To facilitate inhalation and exhalation
• D. To trap pathogens

Answer: (C)

The diaphragm’s main function is to drive ventilation by changing the volume of the thoracic cavity. When it contracts, it flattens and moves downward, increasing the chest cavity’s vertical dimension. This lowers the pressure inside the lungs, causing air to flow in for inhalation. When it relaxes, it returns to its dome shape, decreasing thoracic volume and pushing air out during exhalation. Exhalation is typically passive due to elastic recoil, with abdominal and intercostal muscles aiding only during deep or rapid breathing. This muscle is the primary driver of breathing, while air filtration, oxygen transport, and pathogen trapping are handled by other parts of the system.