The ethmoidal infundibulum is a funnel-shaped[1]/slit-like[2]: 690 /curved[3] opening[1]/passage[4]/space[2]: 690 /cleft[3] upon the anterosuperior portion of the middle nasal meatus[1] (and thus of the lateral wall of[2] the nasal cavity[1]) at the hiatus semilunaris[3][5] (which represents the medial extremity of the infundibulum[2]).

[1] The ethmoidal infundibulum extends anterosuperiorly from its opening into the nasal cavity.

[3] The ethmoid infundibulum leads towards the maxillary hiatus.

[6] The frontonasal duct may or may not drain into the ethmoidal infundibulum - this is determined by the place of attachment of the uncinate process of the ethmoid bone: if the uncinate process is attached to the lateral nasal wall, the frontonasal duct will open directly into the middle nasal meatus; if otherwise, it will drain into the infundibulum.

[2]: 690  In slightly over 50% of subjects, it is directly continuous with the frontonasal duct.