Air sacs. Image credit MediaWiki
ZIMSEC O Level Combined Science Notes:Exhaled air vs inhaled air
- Air which enters the lungs (inhaled air) is different in several regards to air that is passed out (exhaled air)
- Exhaled air contains less oxygen and more carbon dioxide.
- It is also warmer and more moist.
| Component | Inhaled (normal) area | Exhaled air |
|---|---|---|
| Oxygen | 20 | 16 |
| Carbon dioxiode | 0.03 | 4 |
| Nitrogen | 78 | 78 |
| Water vapour approximately | 6 | higher |
- Nitrogen is not absorbed by plants or animals.
- Inhaled air has more oxygen and less carbon dioxide when compared to exhaled air.
An air sac. Image credit wordpress.com
- The composition of inhaled air changes in the alveoli.
- This is where gas exchange takes place.
- Each alveolus is a microscopic structure with capillaries .
- The air in the alveoli has more oxygen than the blood around them.
- The oxygen diffuses into the blood.
- There is more carbon dioxide in the blood than in the alveoli so it diffuses from the blood into the air sacs.
- This two way diffusion is called gas exchange.
- This happens in millions of air sacs every minute of everyday.
- The breathing process makes sure that there is a higher concentration of oxygen in the air sacs that in the blood.
- This means that oxygen will always diffuse into the blood and carbon dioxide outside the blood.
To access more topics go to the Combined Science Notes page.
