What is the primary function of the diaphragm during respiration?

The primary function of the diaphragm during respiration is to allow for lung expansion. As the diaphragm contracts, it moves downward and increases the volume of the thoracic cavity. This expansion creates a negative pressure within the lungs, allowing air to flow in from the outside environment. This process is essential for inhalation, as it facilitates the entry of oxygen into the lungs where it can then be exchanged for carbon dioxide.

In contrast, options such as controlling heart rate, regulating blood pressure, or filtering air are not functions of the diaphragm. The diaphragm is specifically a muscle that plays a crucial role in the mechanical aspect of breathing, emphasizing its significance in respiratory physiology. By focusing on the diaphragm's role in lung expansion, it becomes clear that it is integral to the respiratory cycle.