What 2 structural features of the tracheal lining function to prevent dirt and other particles from entering the lower respiratory tract?

Answer 1

Mucus and cilia. The dirt and other impurities that enter the respiratory tract are trapped by the mucus, in order not to enter the lungs and its structures. But the accumulation of too much mucus in the trachea would impede us from breathing, so the cilia sweep the mucus out of the trachea.