Question

lo 4.3. what are the main functions of the upper respiratory system?
filter, cool, and dehumidify air
filter, warm, and humidify air
produce mucus to line the lungs
absorb oxygen from air
cool and dry air

Explanation:

The upper respiratory system includes structures like the nose, nasal cavity, pharynx, etc. The nasal cavity has cilia and mucus to filter out dust and particles. The blood vessels in the nasal mucosa warm the air, and the mucus (from goblet cells) humidifies the air. These functions prepare the air for the lungs.

• Option 1: "Filter, cool, and dehumidify air" is incorrect. The upper respiratory system warms and humidifies, not cools and dehumidifies.
• Option 2: "Filter, warm, and humidify air" is correct as explained above.
• Option 3: "Produce mucus to line the lungs" is wrong. The upper respiratory system (e.g., nasal cavity) produces mucus, but its main role is in the upper tract (filtering, warming, humidifying), not specifically to line the lungs.
• Option 4: "Absorb oxygen from air" is incorrect. Oxygen absorption mainly occurs in the alveoli of the lungs (lower respiratory system).
• Option 5: "Cool and dry air" is wrong. As mentioned, the upper respiratory system warms and humidifies.

Answer:

Filter, warm, and humidify air