Question

How do the lungs clear out dust that settles in them and sticks to inner surface of their walls?

Answer 1

Explanation:

Tiny hairs called cilia, covering the walls of the air tubes, move the mucus upward and out into the throat, where it is either coughed up and spat out, or swallowed. The air reaches the tiny air sacs (alveoli) in the inner part of the lungs with any dust particles that avoided the defenses in the nose and airways.