trachea, lung, bronchi bronchioles, alveoli ventilation- inhalation diaphragm contracts and flattens, external intercostal muscles contract, ribs move up and out, volume increases, pressure decreases so air moves down pressure gradient into lungs. exhalation- diaphragm relaxes and forms dome-shape, internal intercostal muscle contract, volume decrease, pressure increases, air moves down pressure gradient out of lungs.