The valve of Hasner is
Nasolacrimal duct (NLD) opens into the Inferior meatus through the Hasner`s valve.The direction of NLD--downward, backward, and laterally from the lacrimal sac to the nose, Length- 1.8 cmSphenoid sinus and posterior ethmoids open into the sphenoethmoidal recess (Superior meatus)Frontal, Maxillary and Anterior ethmoids open into the middle meatus.Ref: Hazarika; 3rd ed; Pg 240
Opening of nasolacrimal duct
Sphenoidal sinus opening
Frontal sinus opening
Ethmoidal sinus opening
Nose and paranasal sinuses