Superior view of disarticulated sphenoid, temporal, and occipital bones. The sphenoid and occipital bones are unpaired unlike the temporal bones, which are paired. In this perspective, the body and greater and lesser wings of the sphenoid can be seen. The optic canals are openings in the lesser wings transmitting the optic nerve and ophthalmic artery. Within the greater wing is the foramen ovale for the mandibular and lesser petrosal nerves, and the foramen spinosum for the middle meningeal artery. The foramen lacerum is a space between the body and greater wing of the sphenoid and the apex of the petrous temporal bone. Its floor is filled with fibrocartilage superior to which courses the internal carotid artery (its lacerum segment). The occipital bone contains the foramen magnum, the largest of the cranial foramina, which transmits the vertebral arteries, spinal accessory nerves, spinal cord and meningeal coverings. Anterior to this foramen is the basilar part of the occipital bone that unites with the dorsum sellae of the sphenoid to form the clivus. The temporal bones articulate with both the sphenoid and occipital bones. Its petrous portion houses and protects middle and inner ear structures and serves as the boundary between the middle and posterior cranial fossae. On its posteromedial surface is the internal acoustic meatus for the facial and vestibulocochlear nerves and the labyrinthine artery. The junction between the petrous bone and clivus, the petroclival fissure, is occupied by the inferior petrosal sinus, which drains the cavernous sinus to the internal jugular vein via the jugular foramen. (Image courtesy of AL Rhoton, Jr.)