Mon Prof Augmenté
Air Sacs and Capillaries
Age 12 · Biology
Tiny air sacs in the lungs are surrounded by blood capillaries. Oxygen moves into the blood, and carbon dioxide moves out into the air sacs.
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In the picture
- Thin air sac wall: the boundary where gases cross.
- Capillary mesh: the red network that carries blood around the sac.
- Blue dot in the wall: oxygen moving from the air sac into the capillary.
- Tan dot in the wall: carbon dioxide moving from the capillary into the air sac.
Examples
- A runner breathing deeply after a race.
- Blowing out a candle slowly.
Key takeaways
- Oxygen enters the blood while carbon dioxide leaves it.
- The walls are very thin so gases can pass quickly.
Quiz: Air Sacs and Capillaries (Age 12)
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In the lungs, what happens to oxygen in the air sacs?
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What happens to carbon dioxide in the lungs?
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Why can gases move quickly between the air sacs and the blood?
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