Endoscopic View Through the Anterior Nasal Aperture. A, Endoscopic view through the anterior nasal aperture of the osseous nasal cavity. The perpendicular plate of the ethmoid bone, vomer, and sphenoid crest forms the osseous nasal septum. The middle and inferior concha project into the nasal cavity. B, Nasal cavity with intact mucosa. The endoscope has been inserted into the left nostril. The ethmoid bullae and the uncinate process, to be exposed as the endoscope advances, are hidden under the middle turbinate in the middle nasal meatus. C, Enlarged view of A. The left ethmoid bulla, a rounded bony protrusion overlying the ethmoid air cells, is situated posterior to the uncinate process on the superolateral wall of the middle meatus. The uncinate process arises from the agger nasi cell, the most anterior air cell of the ethmoid bone, and projects downward and backward to attach to the inferior concha. The uncinate process divides the maxillary hiatus into a smaller anterior part and a larger posterior part called the anterior and posterior fontanelles, respectively. In life, the anterior part is closed by the mucosa, whereas the posterior part forms the infundibulum, leading to the maxillary, frontal as ethmoid ostia. The uncinate process obscures the direct view of the maxillary ostium and semilunar hiatus in the view through the 0 degree endoscope. D, View with intact mucosa. The ethmoid bullae and uncinate process are positioned lateral to the middle turbinate in the middle meatus. E, Anterior view of the clivus. The pharyngeal tubercle, a good landmark for the demarcation between the middle and lower clivus, is seen in midline, whereas the anteromedial edge of the jugular foramen, which sits at the junction of the middle and lower clivus, may be difficult to see through the nasal cavity. The small groove for the insertion of the rectus capitis anterior muscle is seen at the upper anterior edge of the occipital condyle. F, Anterior view of the opening from the nasal cavity into the nasopharynx. The tubal prominence is seen behind the ostium of the eustachian tube. The fossa of Rosenmüller projects laterally behind the tubal elevation. The pharyngeal tubercle and longus capitus underlie the mucosa. (Images courtesy of AL Rhoton, Jr.)