What is the primary function of the diaphragm during respiration?

• A. To elevate the ribs and expand the chest cavity
• B. To separate the thoracic and abdominal cavities
• C. To facilitate the exchange of gases
• D. To contract and increase lung volume vertically

Answer: (D)

The primary function of the diaphragm during respiration is to contract and increase lung volume vertically. When the diaphragm contracts, it moves downward, which expands the thoracic cavity. This increase in volume creates a negative pressure within the lungs relative to the atmospheric pressure, allowing air to rush in and fill the lungs. This process is essential for inhalation and plays a vital role in the mechanics of breathing.

Inhalation relies heavily on this action of the diaphragm, as it allows for a significant and efficient intake of air. The diaphragm effectively facilitates a deeper breath compared to just relying on rib movement alone. When the diaphragm relaxes, it returns to its dome shape, which helps push air out of the lungs during exhalation by reducing the volume of the thoracic cavity. Thus, the contraction of the diaphragm directly impacts lung volume and airflow during respiration.