2.1 Breathing
Located in the front of respiratory tract, nasal cavity deals to offer clean air with proper temperature and humidity to the bellows. The air can be filtered throughly by moving like this(look at the picture) inside nasal cavity and be measured to proper temperature and humidity.

2.2 The cleanness and filtration function
This is composed of three parts. First , the crisscrossed vibrissa can prevent the big harmful granule like the dust and float;Second, the mucus felt stick the small granule like germs, dust, chemical and heavy metal ., etc ;Third, the nasal cilia transfers mucus felt adhered with germs to throat , then they are wiped out of the body or go into the stomach .

2.3 Measuring the temperature and humidity
The nasal cavity secrete 1000ml mucous and 70% of them are used to moisten the air；nasal cavity can adjust the temperature to 33-35 degree to suit the resperitary tract .

2.4 Plfactory perception
There is a scent mucosa in upper nasal mucosa which can contact the scent molecule in the nasal cavity.     

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