Final answer:
The respiratory system is protected by multiple defense mechanisms beyond first-line immunity, including the mucociliary escalator effect and alveolar macrophages.
Explanation:
False. The respiratory system is protected by a variety of defenses beyond first-line immune mechanisms. For example, the mucociliary escalator effect, consisting of mucus-producing cells and cilia, helps trap and remove particles and pathogens from the respiratory tract. Additionally, alveolar macrophages in the lower respiratory tract efficiently eliminate microbes that evade initial defenses. These multiple layers of defense work together to keep the respiratory system free from colonized microbes.
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