The lungs have gotten used to their size and shape, and they are comfortable this way. When a person forcibly exhales, it constricts the lungs. When a person relaxes, the lungs return to their standard shape as they took in air. The only ventilation is the trachea, and it forces air in.
<span>It is a vacuum effect. The lungs have gotten used to their size and shape, and they are comfortable this way. When a person forcibly exhales, it constricts the lungs. When a person relaxes, the lungs return to their normal shape as they took in air. The only ventilation is the trachea, and it forces air in.</span>
