Respiratory System: How Air Is Filtered Before Reaching the Lungs

Before air reaches the lungs, it undergoes filtration, conditioning, and cleaning:

1. Nasal filtration – Hairs and mucus trap dust, pollen, microbes.
2. Warming & humidification – Nasal blood vessels warm air; mucus adds moisture.
3. Pharyngeal & laryngeal passage – Serve as conduits.
4. Tracheal mucociliary escalator – Cilia sweep mucus and trapped particles upward.
5. Bronchial divisions – Trachea branches into bronchi, then bronchioles.
6. Alveolar gas exchange – Thin-walled alveoli allow O₂/CO₂ diffusion.

This processing ensures air is clean, body-temperature, humidified, and ready for gas exchange.