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. When the anterior end of the uncinate process fuses with the anterior part of the bulla, however, this continuity is interrupted and the frontonasal duct then drains directly into the anterior end of the middle meatus.[6]
References
^ abcdefgMoore, Keith L.; Dalley, Arthur F.; Agur, Anne M. R. (2017). Essential Clinical Anatomy (6th ed.). Lippincott Williams & Wilkins. pp. 966–967. ISBN978-1496347213.