① showing trachea, ② showing lung and ③ showing diaphragm; Inhalation process When inhaling, the diaphragm and intercostal muscles contract, so that the chest is enlarged up and down, and the chest volume is enlarged, so that the air pressure in the lungs is less than the external atmospheric pressure, and the external gas enters the lungs, forming an active inhalation movement; When the diaphragm and the external intercostal muscle relax, the ribs and sternum return to their original positions due to their own gravity and elasticity. As a result, the volume of the chest cavity is reduced, and the lungs are also retracted, resulting in the air pressure in the lungs being higher than the outside air pressure, and the air in the lungs is discharged from the lungs, forming a passive expiratory movement. In the figure, the top of diaphragm A rises and the lungs contract, indicating exhalation, while in the figure, the top of diaphragm B falls, the chest volume increases and the lungs expand, indicating inhalation.

So, the answer is: 2; ③; Inhale; Increase; develop