Which structure opens into the superior meatus of the nasal cavity?

Which structure opens into the superior meatus of the nasal cavity?

• A. Frontal sinus
• B. Maxillary sinus
• C. Posterior ethmoid sinus
• D. Sphenoid sinus

Answer: (C)

Drain openings from the paranasal sinuses are not all into the same nasal recess. The posterior ethmoid air cells drain upward into the superior meatus, which sits under the roof of the nasal cavity beneath the superior concha. By contrast, the frontal and maxillary sinuses drain into the middle meatus (via the frontonasal duct/infundibulum for the frontal, and the maxillary ostium for the maxillary). The sphenoid sinus drains into the sphenoethmoidal recess, which is above the superior meatus. Therefore, the structure that opens into the superior meatus is the posterior ethmoid sinus.

Drain openings from the paranasal sinuses are not all into the same nasal recess. The posterior ethmoid air cells drain upward into the superior meatus, which sits under the roof of the nasal cavity beneath the superior concha. By contrast, the frontal and maxillary sinuses drain into the middle meatus (via the frontonasal duct/infundibulum for the frontal, and the maxillary ostium for the maxillary). The sphenoid sinus drains into the sphenoethmoidal recess, which is above the superior meatus. Therefore, the structure that opens into the superior meatus is the posterior ethmoid sinus.