Superolateral views of right orbit and middle fossa. Bones of the anterior and middle fossa floors have been removed to show underlying contents. The trigeminal nerve crosses the apex of the petrous bone and its ganglion occupies the trigeminal depression. From here, its ophthalmic branch (sensory only) passes forward through the superior orbital fissure to enter the orbit. Its lacrimal nerve branch courses along the upper lateral wall of the orbit toward the lacrimal gland. The maxillary branch (sensory only) of the trigeminal nerve passes through the foramen rotundum to the pterygopalatine fossa. The mandibular branch (both sensory and motor) passes through the foramen ovale to enter the roof of the infratemporal fossa. The superior head of the lateral pterygoid muscle can be seen in this fossa and lateral to it, cut fibers of the temporalis. Posterior to the trigeminal ganglion the roof of the internal auditory canal has been drilled to expose the facial nerve. At the end of the canal the nerve ends at the geniculate ganglion from which arises the greater superficial petrosal nerve carrying preganglionic parasympathetic fibers. This nerve unites with the deep petrosal nerve carrying postganglionic sympathetic fibers. The petrous segment of the internal carotid artery has been exposed to show these fibers. Their union forms the nerve of the pterygoid canal (Vidian nerve). This nerve passes into the pterygoid canal, which opens into the pterygopalatine fossa. Here, parasympathetic fibers will synapse in the pterygopalatine ganglion and postganglionic fibers will be distributed, along with postganglionic sympathetic fibers, to areas supplied by branches of the maxillary nerve. These branches typically are accompanied by branches of the maxillary artery. This artery enters the pterygopalatine fossa from the infratemporal fossa via the pterygomaxillary fissure. The oculomotor, trochlear, and abducens nerves enter the orbit with the ophthalmic nerve. In its course, the abducens nerve passes beneath Gruber's ligament (petrosphenoid ligament) within Dorello's canal to enter the cavernous sinus. The cavernous, clinoid (between the proximal and distal dural rings), and supraclinoid segments of the internal carotid artery can be seen, with the ophthalmic artery arising from the latter segment. The ophthalmic artery and optic nerve enter the orbit through the optic canal.  (Image courtesy of AL Rhoton, Jr.)