<P> There are two important foramina, or windows, two important fissures, or grooves, and one canal surrounding the globe in the orbit . There is a supraorbital foramen, an infraorbital foramen, a superior orbital fissure, an inferior orbital fissure and the optic canal, each of which contains structures that are crucial to normal eye functioning . The supraorbital foramen contains the supraorbital nerve, the first division of the trigeminal nerve or V1 and lies just lateral to the frontal sinus . The infraorbital foramen contains the second division of the trigeminal nerve, the infraorbital nerve or V2, and sits on the anterior wall of the maxillary sinus . Both foramina are crucial as potential pathways for cancer and infections of the orbit to spread into the brain or other deep facial structures . </P> <P> The optic canal contains the optic nerve (cranial nerve II) and the ophthalmic artery, and sits at the junction of the sphenoid sinus with the ethmoid air cells, superomedial and posterior to structures at the orbital apex . It provides a pathway between the orbital contents and the middle cranial fossa . The superior orbital fissure lies just lateral and inferior to the optic canal, and is formed at the junction of the lesser and greater wing of the sphenoid bone . It is a major pathway for intracranial communication, containing cranial nerves III, IV, VI which control eye movement via the extraocular muscles, and the ophthalmic branches of cranial nerve V, or V1 . The second division of the trigeminal nerve enters the skull base at the foramen rotundum, or V2 . The inferior orbital fissure lies inferior and lateral to the ocular globe at the lateral wall of the maxillary sinus . It is not as important in function, though it does contain a few branches of the maxillary nerve and the infraorbital artery and vein . Other minor structures in the orbit include the anterior and posterior ethmoidal foramen and zygomatic orbital foramen . </P> <P> The bony walls of the orbital canal in humans do not derive from a single bone, but a mosaic of seven embryologically distinct structures: the zygomatic bone laterally, the sphenoid bone, with its lesser wing forming the optic canal and its greater wing forming the lateral posterior portion of the bony orbital process, the maxillary bone inferiorly and medially which, along with the lacrimal and ethmoid bones, forms the medial wall of the orbital canal . The ethmoid air cells are extremely thin, and form a structure known as the lamina papyracea, the most delicate bony structure in the skull, and one of the most commonly fractured bones in orbital trauma . The lacrimal bone also contains the nasolacrimal duct . The superior bony margin of the orbital rim, otherwise known as the orbital process, is formed by the frontal bone . </P> <P> The roof (superior wall) is formed primarily by the orbital plate frontal bone, and also the lesser wing of sphenoid near the apex of the orbit . The orbital surface presents medially by trochlear fovea and laterally by lacrimal fossa . </P>

What is the name of the bone that makes up most of the posterior surface of orbit