What is the primary function of the diaphragm during respiration?

The primary function of the diaphragm during respiration is to contract and expand the thoracic cavity. When the diaphragm contracts, it moves downward, increasing the volume of the thoracic cavity. This increase in volume creates a negative pressure within the thoracic cavity, allowing air to flow into the lungs during inspiration. Upon relaxation, the diaphragm moves back to its dome-shaped position, decreasing the thoracic cavity's volume and facilitating exhalation as air is pushed out of the lungs.

In this context, the diaphragm plays a critical role in providing the mechanical action needed for effective breathing. The other options do not accurately describe the diaphragm's primary role. For instance, controlling airway resistance typically involves the bronchial muscles rather than the diaphragm. Minimizing lung volume contradicts the diaphragm's function, as it actively works to increase volume during inhalation. Increasing cardiac output is unrelated to the diaphragm's respiratory role, as cardiac function is primarily managed by the heart rather than this muscle.