A, The structures anterior to the left orbital apex and the portion of the maxilla above the alveolar process have been removed to expose the nasal septum, which is formed posteriorly by the vomer, above by the perpendicular plate of the ethmoid, and anteriorly by the septal cartilage. B, The nasal septum and anterior wall of the sphenoid sinus have been removed. This exposes the superior, middle, and inferior conchae and a midline septum within the sphenoid sinus. The ethmoid air cells are exposed in the medial wall of the right orbit. The part of the sphenoid sinus medial to and below the orbital apex has been opened. C, The left half of the facial skeleton, including the left half of the maxilla and orbit, has been removed to expose the left side of the nasal septum, which is formed above by the perpendicular plate of the ethmoid bone and below by the vomer. The palate is formed anteriorly by the maxilla and posteriorly by the horizontal plate of the palatine bone. D, The nasal septum has been removed. The inferior concha is a separate bone, which protrudes into the nasal cavity from the maxilla. The middle and superior concha are appendages of the ethmoid bone. The maxillary ostium is located between the perpendicular plate of the palatine bone behind, the ethmoid superiorly, and the medial maxillary wall below. The maxillary and frontal sinus and the anterior ethmoid air cells drain into the middle meatus, and the posterior ethmoid air cells drain into the superior meatus. E, The anterior nasal aperture is formed above by the nasal bones and laterally and below by the maxilla. The anterior part of the osseous nasal septum is formed above by the perpendicular ethmoid plate and below by the vomer. The inferior concha, a separate bone, and the middle concha, an appendage of the ethmoid bone, are visible through the aperture. F, Posterior view of the posterior nasal aperture. The floor of the posterior aperture is formed by the horizontal plate of the palatine bone. The lateral margin is formed by the medial plate of the pterygoid process and is joined anteriorly by the perpendicular plate of the palatine bone, which forms the part of the lateral nasal wall between the maxilla and the medial pterygoid plate. Posteriorly, the middle concha is much more prominent than the inferior concha and often must be displaced laterally in the transsphenoidal approach to the sphenoid sinus. The vomer extends from the upper surface of the hard palate to the body of the sphenoid bone and separates the paired nasal cavities at the posterior aperture. (Images courtesy of AL Rhoton, Jr.)