Breathing and the Respiratory System
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Diagram showing the structure of the lung
The lungs consist of a network of thin tubes that each end up in a tiny air sac that is surrounded by blood capillaries
The capillaries and air sac both have very thin walls only one cell thick so gases can easily pass backwards and forwards
When you breath in:
- Strong muscles pull the diaphragm down and the rib cage expands.
- This makes air enter the lungs through the mouth
Look at this link to see what happens
Table showing a comparison between the composition of inhaled with exhaled air.
| Gas | Air entering lungs – Inhaled air | Air leaving lungs – Exhaled air |
| Oxygen | 21% | 16% |
| carbon dioxide | 0.03% | 3% |
| Nitrogen | 78% | 78% |
| water vapour | small amount | significantly moist |
Note:
Exhaled air has less oxygen
Exhaled air has more carbon dioxide
Nitrogen is not needed by our body so stays the same
Exhaled air has more water vapour