What primary function does the diaphragm serve in the respiratory system?

The diaphragm is a crucial muscle in the respiratory system primarily responsible for facilitating breathing. When you inhale, the diaphragm contracts and moves downward, creating a vacuum effect that allows air to flow into the lungs. This action increases the volume of the thoracic cavity, which reduces pressure inside the lungs compared to the outside atmosphere, enabling fresh air to enter. Conversely, during exhalation, the diaphragm relaxes and moves back up, pushing air out of the lungs.

This mechanism of contraction and relaxation directly enables the process of breathing, which is vital for gas exchange in the body, as it allows oxygen to enter the bloodstream and carbon dioxide to be expelled. Other options such as regulating body temperature, digesting food, or circulating blood represent different physiological functions that do not directly involve the mechanical process of respiration.