Globally, by the human organism, e.g., hands in front of face. Internally, mucus protects the passages from drying out and from some germs.
Clears the nasal passages, because a sneeze is caused by irritation or itchiness in your nose or nasal passages.
nostrils
No, as they have no lungs or nasal passages.
nasal septum
Nostrils are also known as nasal passages or nasal cavities.
deviated septum
Lets you smell and filters out germs
No, if there were it would be called clear nasal passages.
No, clams don't have nasal passages or lungs.
Rhinitis is inflammation in the nasal passages.
between the nasal passages and the diaphragm
the uvula