Valve of Hasner
Ref BDC volume3,6th edition pg 76Nasolacrimal duct begins at the lower end of the lacrimal sac, runs downwards, backward and laterally and opens into the inferior meatus of the nose.A fold of mucous membrane called hasners valve forms an imperfect valve at the lower end of the duct.
Opening of nasolacrimal duct
Sphenoidal sinus opening
Frontal sinus opening
Ethmoidal sinus opening
Head and neck