A, This cross section extends through the nasal cavity, orbits, and maxillary and ethmoid sinuses. The ethmoid sinuses are situated in front of the sphenoid sinus. The middle and inferior turbinates have been preserved. B, The anterior wall of the sphenoid sinus has been opened to expose a multiseptated sinus and the anterior sellar wall. The left turbinates have been removed. Part of the posterior wall of the left maxillary sinus has been removed to expose the greater palatine artery which arises from the maxillary artery in the pterygopalatine fossa. The internal carotid arteries form serpiginous prominences in the lateral wall of the sphenoid sinus. C, The mucosa and bony wall of the sphenoid sinus have been removed to expose both the internal carotid arteries, which form the lateral limit of the transnasal exposure of the upper clivus. The pituitary gland has been exposed. Additional posterior wall of the left maxillary sinus has been removed to expose the infratemporal fossa, which contains the branches of the maxillary artery, the pterygoid muscles, pterygoid venous plexus, and branches of the mandibular nerve. The nasopharyngeal mucosa covering the longus capitis and the lower clivus is exposed in the interval between the palate and the vomer. D, Enlarged view of the sphenoid sinus and sellar region. The anterior surface of the upper clivus is exposed below the pituitary gland. The lateral clival exposure is limited at this level by the internal carotid arteries. E, Oblique view. The medial wall of the left cavernous sinus has been opened to expose the abducens and oculomotor nerves. The pterygopalatine fossa is located below the orbital apex. The maxillary nerve passes through the foramen rotundum and gives rise to the communicating rami to the pterygopalatine ganglion and the infraorbital nerve that courses along the floor of the orbit. F, Enlarged view of the structures in the medial cavernous sinus. The ophthalmic artery courses below the optic nerve in the optic canal. (Images courtesy of AL Rhoton, Jr.)