Semilunar hiatus and paranasal sinuses
The frontal sinus is open at the top end and open to the middle nasal meatus。
The maxillar sinus is open at the lateral wall and open to the middle nasal meatus.
Anterior part of the ethmoidal sinus(ethmoidal cells) opens to the middle nasal meatus through the semilunar hiatus
   Middle part open to the middle nasal meatus through surface of the ethmoidal bulla. Posterior part open into the superior nasal meatus.