Question

Why don't lungs collapse even after forceful expiration?

Answer 1

Forceful expiration:

1. The lungs do not collapse completely even after forceful expiration because of the presence of air even after forceful expiration and cartilaginous tissue on the tubules of the respiratory tract. ​
2. Residual volume: The air inside the lungs even after forceful expiration is called the residual volume. The presence of this air stops the lungs from collapsing completely.
   
3. Cartilaginous tissue: The cartilaginous tissue present around the respiratory tract including the trachea, bronchi and bronchioles. This allows the movement of expiration to occur, but stops the lung from collapsing during expiration.