USMLE

Respiratory Defense Systems

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Respiratory
  1. Respiratory Overview
  2. Airway Anatomy
  3. Alveoli
  4. Breathing Mechanics
  5. Gas Exchange in Tissues
  6. Nervous Control of Breathing
  7. Respiratory Defense Systems
  • Respiratory Defense Systems
    • Airway
      • Nasal hairs
        • Filter out large dust particles
      • Mucociliary escalator
        • Lining of trachea has layer of mucus over cilia
        • Trap particles in mucus and move them up out of airway
          • Mucus can be spit/coughed out or swallowed and destroyed by stomach acid 
        • Mucus traps particulate matter and bacteria 
          • Thick, sticky substance secreted by epithelial cells
        • Cilia beat synchronously to move mucus and dust back toward pharynx
          • Small, hair-like organelles projecting from the epithelium that move back and forth
    • Alveolar macrophages
      • Large white blood cells in alveoli
      • Engulfs (phagocytizes) and digests foreign material