Kaplan Nursing Entrance Exam Practice 2025 – Comprehensive Prep

The primary role of the diaphragm during respiration is to create pressure differences in the thoracic cavity, which facilitates the intake and expulsion of air from the lungs. When the diaphragm contracts, it moves downward, increasing the volume of the thoracic cavity and decreasing the internal pressure. This pressure difference allows air to flow into the lungs as the body inhales. Conversely, when the diaphragm relaxes, it moves upward, reducing the volume and increasing the pressure, which helps to push air out during exhalation. This fundamental mechanism is crucial for ventilating the lungs and ensuring adequate oxygen supply to the body.

The other functions mentioned, such as filtering air, exchanging gases, or circulating blood, do not primarily depend on the diaphragm's action. Although the diaphragm influences breathing, gas exchange occurs in the alveoli of the lungs, and blood circulation is managed by the heart and blood vessels. Thus, the diaphragm’s role is specifically about creating the necessary pressure changes for effective respiration.