What do goblet cells and cilia have in common? Both moisten the air. Both filter the air. Both secrete mucus. Both diffuse oxygen.

Both of them secrete mucus. The protective function of cilia in the trachea is moving the sheet of mucus that are contaminated, away from the lungs, toward the throat for swallowing. Goblet cells secrete the mucus's major components which is called the gel-forming mucins.