What regulates the movement of air in and out lungs?

The movement of air in and out of the lungs is regulated by the contraction and relaxation of the diaphragm and the intercostal muscles. The diaphragm is a large, dome-shaped muscle located at the bottom of the rib cage. When the diaphragm contracts, it pulls the lungs downward, which creates a negative pressure in the pleural cavity (the space between the lungs and the chest wall). This negative pressure causes the lungs to expand and air to be drawn in through the nose or mouth. The intercostal muscles are located between the ribs. When they contract, they pull the ribs upward and outward, which also increases the volume of the pleural cavity and causes the lungs to expand. The relaxation of the diaphragm and the intercostal muscles causes the lungs to recoil and air to be expelled through the nose or mouth.