Final answer:
The respiratory system protects itself from infection using the mucociliary escalator, which includes mucus-producing cells and cilia. The mucus traps pathogens and the cilia sweep them away.
Step-by-step explanation:
The respiratory system protects itself from infection by using the mucociliary escalator, which includes mucus-producing cells and hair-like cilia.
The mucus traps particles and pathogens in the incoming air, and the cilia continually move to sweep the mucus and trapped debris away from the lungs and toward the outside of the body. This helps protect the respiratory tract from infection.