The diaphragm (the muscle below the lungs) contracts and moves downward, flattening out.
Inhalation, or breathing in, is the active phase of respiration where air is drawn into the lungs, providing oxygen needed for cellular metabolism. It is a complex process controlled by muscle movements that increase the volume of the chest cavity, lowering the pressure inside and allowing air to enter. The Mechanics of Inhalation ms inhale
Muscles between the ribs contract, pulling the rib cage up and out. The diaphragm (the muscle below the lungs) contracts
Air rushes in through the nose or mouth, traveling down the trachea, through the bronchial tubes, and into the alveoli (air sacs). Physiological Role flattening out. Inhalation
How the Lungs Work - What Breathing Does for the Body - nhlbi - NIH