Question

what is the purpose of hair in nostrils and mucus lining in respiratory passage

Answer 1

They trap dust and dirt nd they don't allow dust and dirt to enter the lungs upto a great extend.

Answer 2

Hair in the nose is one of the body's first line of defense against harmful environmental pathogens such as germs,fungus,spores etc... Another purpose is to provide additional humidity to the inhaled air.As the air passes through the nasal passage mucous and hair provides heat and moisture.
       Hope it helps u...