What is the primary muscle responsible for respiration?

The diaphragm is the primary muscle responsible for respiration due to its central role in the breathing process. When the diaphragm contracts, it moves downward, creating a negative pressure in the thoracic cavity, which allows air to flow into the lungs. This movement is crucial for inhalation and is responsible for a significant portion of the volume of air that is drawn in with each breath.

The diaphragm’s anatomical shape and placement make it uniquely suited to function as the main respiratory muscle, distinguishing it from other muscles associated with breathing. While intercostal muscles support respiration by aiding in the expansion and contraction of the thoracic cavity during breathing, their role is secondary compared to the diaphragm's fundamental function.

The abdominal muscles do play a role in exhalation, especially during forceful breathing, but they are not primarily responsible for the initial act of inhalation. Similarly, while the rectus abdominis is a specific abdominal muscle, its function is more related to trunk flexion than to the primary process of respiration.