Select the correct events that occur during inspiration. (a) Contraction of diaphragm (b) Contraction of…

INSPIRATION: Inspiration is an active process involving the contraction of the muscles. The external intercostal muscles contract, making the ribs move outward, sideward and upward. This increases thoracic volume. Simultaneously the muscles of the diaphragm also contract and the diaphragm becomes a flattened sheet, further increasing the thoracic volume. This decreases intrapleural pressure and the pressure in the lungs. This decrease in the pressure makes the air rush in from the surrounding atmosphere into the lungs. The lungs being elastic expand to accommodate the air rushing in. The air pressure in the lungs becomes equal to the atmospheric pressure. Even though the external intercostal muscles are necessary for breathing the diaphragm is the principal organ of breathing.