The opening of the maxillary sinus is near the top of the base, in the center of the semilunar hiatus, which grooves the lateral wall of the middle nasal meatus.
Relationships of the maxillary sinus are as follows:
The superolateral surface (roof) is related above to the orbit.
The anterolateral surface is related below to the roots of the upper molar and premolar teeth and in front to the face.
The posterior wall is related behind to the infratemporal fossa.