Answers

2016-06-15T18:58:44+08:00
Two plastic bottle- chest cavity
Two straws- bronchi
Two balloons- lungs
Large balloon- diaphragm

The two balloons expand.

The two balloons return to their original size.

--Mizu
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thanks a lot!!!!
2016-06-15T20:01:01+08:00
The lung model constructed represent to a breathing system 

when u pull down the ballon the air goes in 

when u push the up the ballon the air goes out 
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