All of the following structures open into the middle meatus, EXCEPT:
Posterior ethmoid sinus opens into superior meatus. Anterior ethmoid cells are divided into frontal recess cells, which open into the frontal recess of the middle meatus, infundibular cells which open into the ethmoid infundibulum and and bullae or middle ethmoid cells which open into the middle meatus. Maxillary sinus drain into the middle meatus of nasal cavity. The frontal sinus opens into the infundibulum of middle meatus through frontonasal duct. Sphenoid sinus opens into the sphenoethmoidal recess above and behind the superior nasal concha.
Ant. ethmoidal sinus
Post. ethmoidal sinus
Frontonasal duct
Maxillary sinus