Final answer:
The first line of filtration in airway protection is called the mucociliary escalator. Mucus traps particles and pathogens, while cilia move them away from the lungs.
Step-by-step explanation:
The first line of filtration in airway protection is called the mucociliary escalator. This mechanism is part of the respiratory system and it includes mucus-producing cells and cilia. Mucus traps particles and pathogens in the incoming air, while cilia move the mucus and trapped debris away from the lungs.