Pulmonary ventilation IIVersion en ligne PAGE 57 par Secundaria Digital 1 Inspiration 2 Expiration Air enters the lungs The diaphragm flattens and lowers The ribs rise outwards The capacity of the ribcage is increases The lungs become enlarged, increasing their volume It releases air from the lungs The diaphragm relaxes, curves and rises. The ribs sink The ribcage capacity is reduced, so it shrinks The lungs reduce their volume.