G, Middle concha has been removed. This exposes the uncinate process of the ethmoid bone. The ethmoid infundibulum, which drains the anterior ethmoid air cells and sometimes joins the frontal duct, opens downward above the uncinate process. H, Oblique anterior view of the sphenoid sinus. The anterior wall of the left half of the sphenoid sinus has been removed. The optic canal is located between the body of the sphenoid, the optic strut, the anterior clinoid process, and the anterior root of the lesser sphenoid wing. The sphenoid ostia open, just above the superior concha, into the nasal cavity. I, Lateral wall of the nasal cavity after removal of the concha. The upper part of the lateral wall of the nasal cavity is formed by the ethmoid air cells. The lower part of the lateral wall is formed, from anterior to posterior, by maxilla, perpendicular palatal plate, and the pterygoid process and medial pterygoid plate. The palate is formed anteriorly by the palatal plate of the maxilla and posteriorly by the horizontal plate of the palatine bone. J, Section through the nasal cavity and both maxillae. The maxillary sinuses form part of the lateral wall of the nasal cavity and drain through the middle meatus into the nasal cavity. The cribriform plate is located above the nasal cavity in the midline. The part of the nasal septum below the cribriform plate is formed by the perpendicular ethmoid plate. The vomer forms the lower and posterior parts of the nasal septum. The wings of the vomer spread laterally along the lower surface of the sphenoid body. The ethmoid air cells are in the upper part of the lateral wall of the nasal cavity. (Images courtesy of AL Rhoton, Jr.)