Answers

2015-06-09T19:50:35+08:00
When you inhale 
- the intercostal muscles contract, expanding the ribcage 
- the diaphragm contracts, pulling downwards to increase volume of the chest 
- pressure inside the chest is lowered and air is sucked into the lungs 

When you exhale 

- the intercostal muscles relax, ribcage drops inwards and outwards 
- the diaphragm relaxes, moving back upwards to decrease volume of the chest 
- pressure inside the chest increases and air is forced out 

(I forgot this so I asked someone to give me this..."
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2015-06-11T19:23:39+08:00
Basically gas exchange takes place. Oxygen is carried in when you inhale and carbon dioxide is carried out when you exhale.
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