Cut and remove the middle nasal turbinate to view the middle meatus. In the superolateral wall of the middle meatus, identify the prominent elevation, called the ethmoid bulla and inferior to it, the uncinate process. Immediately beneath the ethmoid bulla is a crescent-shaped opening, called the hiatus semilunaris. At its anterior and superior end, the hiatus semilunaris expands into the infundibulum. The nasofrontal duct from the frontal sinus opens into the infundibulum.
The openings of the anterior ethmoidal air cells and the ostium of the maxillary sinus usually open into the hiatus semilunaris. The middle ethmoidal air cells open onto the surface of the ethmoid bulla (see Figure 33.4).
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