Lesson 12 of 17
Gases swap at the alveoli
Show on a big screenAir reaches the alveoli, the small sacs of air in the lungs. Then two gases swap places.
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The idea
An alveolus has a very thin wall. Because the wall is thin, gases pass across it easily. Tiny blood tubes press against the wall.
Swap means each gas goes the other way.
Step 1 of 4
- One alveolus, with a ring of blood round it.
- Oxygen passes from the air into the blood.
- Carbon dioxide passes from the blood into the air.
- The blood carries the oxygen to every part of the body.
Oxygen passes from the air into the blood. Carbon dioxide passes from the blood into the air.
About one fifth of the air we breathe in is oxygen. That is about 21 parts in every 100.
So breathed-out air has less oxygen than breathed-in air. Breathed-out air also has more carbon dioxide.
Try the lab to finish this lesson.