What is the primary muscle responsible for respiration?

The primary muscle responsible for respiration is the diaphragm. This dome-shaped muscle sits at the base of the thoracic cavity and separates the chest from the abdomen. When the diaphragm contracts, it moves downward, increasing the volume of the thoracic cavity. This expansion creates a negative pressure within the lungs, allowing air to flow in from the exterior to fill the lungs—this process is known as inhalation.

When the diaphragm relaxes, it moves back to its dome shape, resulting in a decrease in the volume of the thoracic cavity and promoting exhalation as air is pushed out of the lungs. The diaphragm is highly efficient and is responsible for the majority of the air movement during normal, quiet breathing. It plays a crucial role in regulating the respiratory cycle and is essential for adequate gas exchange in the body.

Other muscles, such as the external intercostals and abdominal rectus, aid in respiration but are not the primary drivers of the process like the diaphragm is. The lungs themselves are not muscles and therefore do not possess any muscular function, and they rely on muscular contractions to facilitate breathing.