![]() ![]() The superior ophthalmic vein is a sigmoidal vessel along the superior margin of the orbital canal that drains deoxygenated blood from surrounding musculature. The movement of the eye is controlled by six distinct extraocular muscles, a superior, an inferior, a medial and a lateral rectus, as well as a superior and an inferior oblique. Lateral margin: zygomatic bone and frontal bone.Medial margin: frontal bone and maxilla.Inferior margin: maxilla and zygomatic bone.The following bones take part in their formation: The base, orbital margin, which opens in the face, has four borders. The lateral wall is the thickest wall of the orbit, important because it is the most exposed surface, highly vulnerable to blunt force trauma. The bones meet at the zygomaticosphenoid suture. The lateral wall is formed by the frontal process of zygomatic and more posteriorly by the orbital plate of the greater wing of sphenoid. It is the thinnest wall of the orbit, evidenced by pneumatized ethmoidal cells. The medial wall is formed primarily by the orbital plate of ethmoid, as well as contributions from the frontal process of maxilla, the lacrimal bone, and a small part of the body of the sphenoid. The floor is separated from the lateral wall by inferior orbital fissure, which connects the orbit to pterygopalatine and infratemporal fossa. Near the middle of the floor, located infraorbital groove, which leads to the infraorbital foramen. ![]() Medially, near the orbital margin, is located the groove for nasolacrimal duct. The floor (inferior wall) is formed by the orbital surface of maxilla, the orbital surface of zygomatic bone and the minute orbital process of palatine bone. The orbital surface presents medially by trochlear fovea and laterally by lacrimal fossa. 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 superior bony margin of the orbital rim, otherwise known as the orbital process, is formed by the frontal bone. The lacrimal bone also contains the nasolacrimal duct. 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 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. Teal = Nasal bone (illustrated but not part of the orbit) Other minor structures in the orbit include the anterior and posterior ethmoidal foramen and zygomatic orbital foramen. It is not as important in function, though it does contain a few branches of the maxillary nerve and the infraorbital artery and vein. The inferior orbital fissure lies inferior and lateral to the ocular globe at the lateral wall of the maxillary sinus. The second division of the trigeminal nerve enters the skull base at the foramen rotundum, or V2. 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 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 provides a pathway between the orbital contents and the middle cranial fossa. The optic canal contains the ( 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. Both foramina are crucial as potential pathways for cancer and infections of the orbit to spread into the brain or other deep facial structures. 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. The supraorbital foramen contains the supraorbital nerve, the first division of the trigeminal nerve or V1 and lies just lateral to the frontal sinus. 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. There are two important foramina, or windows, two important fissures, or grooves, and one canal surrounding the globe in the orbit. Each consists of a base, an apex and four walls. The orbits are conical or four-sided pyramidal cavities, which open into the midline of the face and point back into the head. ![]()
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