The main muscle that aids in the passage of air into and out of the lungs is the diaphragm. It is a large, dome-shaped muscle located below the lungs that separates the thoracic cavity from the abdominal cavity.
- When you breathe in (inhale), the diaphragm contracts and moves downward, flattening out. This increases the size of the chest cavity, creating a vacuum that pulls air into the lungs.
- When you breathe out (exhale), the diaphragm relaxes and moves back up into its dome shape. This reduces the chest cavity size, pushing air out of the lungs.
The diaphragm works together with the intercostal muscles (muscles between the ribs) which help expand and contract the rib cage during breathing. However, the diaphragm is the primary and most important muscle responsible for breathing
. In summary, the diaphragm's rhythmic contraction and relaxation drive the main mechanism of air movement in and out of the lungs.
