Mon Prof Augmenté
Gas Exchange in the Alveoli
Age 14 · Biology
Deep in your lungs, millions of tiny air sacs called alveoli are wrapped in thin blood vessels. Oxygen moves from the air into your blood, and carbon dioxide moves from your blood into the air you breathe out.
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In the picture
- Alveolus: a tiny air sac with a wall only one cell thick
- Capillary: a thin blood vessel that turns from oxygen-poor to oxygen-rich
- Oxygen: diffuses from the air in the alveolus into the blood
- Carbon dioxide: diffuses from the blood into the alveolus to be breathed out
Examples
- When you run, you breathe faster so more fresh air reaches your alveoli and more oxygen gets into your blood.
- Fogging up a cold window with your breath shows the warm, moist air your lungs push out, which carries carbon dioxide.
Key takeaways
- Gases move by diffusion, from where there is more of them to where there is less.
- Thin walls and a huge surface area make gas exchange fast.
Quiz: Gas Exchange in the Alveoli (Age 14)
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During gas exchange in the lungs, which way does oxygen move?
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Carbon dioxide moves from the blood into the alveoli. Why does it move in that direction?
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What makes gas exchange in the lungs fast?
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