Ans. C) The natural ostium of the maxillary sinus opens into the infundibulum in the middle meatus

The natural ostium of the maxillary sinus opens into the infundibulum, which lies in the middle meatus. This is a key feature of the osteomeatal complex.

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Other Options:

Option A. The uncinate process lies posterior to the ethmoidal bulla and opens directly into the suprabullar recess: Incorrect. The uncinate process lies anterior to the ethmoidal bulla, and the hiatus semilunaris lies between them. The suprabullar recess lies above the bulla, not connected directly to the uncinate process.

Option B. The space between the uncinate process and ethmoidal bulla is called the infundibulum: Incorrect. The space between the uncinate process and ethmoidal bulla is the hiatus semilunaris (a 2D cleft). The infundibulum is the 3D space into which this cleft opens.

Option D. Haller cells are located between the ethmoidal bulla and uncinate process within the hiatus semilunaris: Incorrect. Haller cells are infraorbital ethmoidal air cells, formed by pneumatization of the roof of the maxillary sinus (orbital floor), not located in the hiatus semilunaris.

Educational Objective:

The natural ostium of the maxillary sinus opens into the infundibulum, a key space in the middle meatus that forms part of the osteomeatal unit.

Ref: PL Dhingra, 6th Ed.; Radiological and endoscopic sinus anatomy references.

Ref: P.L Dhingra Diseases of Ear, Nose and Throat and Head and Neck Surgery, 6th Edition, pg 136

External Nose & Lateral Nasal Wall

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