A, The cross section extends across the nasal cavity, superior and middle turbinates, maxillary sinuses, the orbits near the apex and the ethmoidal sinuses in front of the sphenoid sinus. The zygomatic and infraorbital nerves arise from the maxillary nerve in the pterygopalatine fossa, which is located behind the posterior maxillary wall. The nasal septum is formed above by the perpendicular ethmoid plate, below by the vomer, and anteriorly by the cartilaginous septum. B, The concha and posterior ethmoid air cells have been removed to expose the vomer and the anterior wall of the sphenoid sinus and the sphenoid ostia. The nasolacrimal duct descends along the lateral wall of the nasal cavity. C, Enlarged view. The perpendicular ethmoid plate joins the anterior sphenoid face, and the vomer extends upward to join the inferior sphenoid wall, both in the midline. The posterior ethmoid air cells are located anterior to the lateral part of the sphenoid face and overlap the superolateral margins of the sphenoid ostia. D, The anterior face of the sphenoid has been removed to expose the multiseptated sphenoid sinus and the anterior wall of the sella. The bony prominences over the optic canals are situated in the superolateral margins of the sinus. (Images courtesy of AL Rhoton, Jr.)