Anterior view of orbital apex in coronal section. The lateral masses of the ethmoid bone form the posteromedial wall of the orbit and contain the ethmoid sinus (air cells). The perpendicular plate of ethmoid and vomer form the bony nasal septum. The sphenoid sinus drains into the superior nasal cavity through ostia located within the sphenoethmoidal recess. The roof of the maxillary sinus forms the floor of the orbit. (Image courtesy of AL Rhoton, Jr.)