The orbits are bilateral bony cavities located in the skull, below the anterior cranial fossa and anterior to the middle cranial fossa, with openings present in the upper half of the face, on either side of the root of the nose. Each orbit contains the eyeball, the optic nerve, the extraocular muscles, the lacrimal apparatus, as well as orbital adipose tissue, fascia, and nerves and vessels that supply all of these structures.

Seven bones contribute to the framework of each orbit:

• Maxilla (Read more!)
• Zygomatic bone (Read more!)
• Frontal bone (Read more!)
• Ethmoid (Read more!)
• Lacrimal bone (Read more!)
• Sphenoid (Read more!)
• Palatine bone (Read more!)

Together these bones give the bony orbit the shape of a pyramid, with its wide base (the orbital rim) opening anteriorly onto the face as the orbital opening, and its apex extending in a posteromedial direction and continuing as the optic canal.

The orbital rim has four margins:

• Supraorbital margin - formed by the orbital part of the frontal bone;
• Infraorbital margin - formed by the zygomatic process of the maxilla, and the orbital process of the zygomatic bone;
• Lateral orbital margin - formed by the frontal process of the zygomatic bone;
• Medial orbital margin - formed by the frontal process of the maxilla, the lacrimal bone, and the orbital part of the frontal bone.

The orbit is composed of four walls:

• Medial wall - formed by the frontal process of the maxilla, lacrimal bone, orbital plate of the ethmoid bone, and body of the sphenoid bone;
• Superior wall - orbital surface of the orbital part of the frontal bone and lesser wing of the sphenoid bone;
• Lateral wall - orbital surface of the greater wing of the sphenoid bone and orbital surface of the zygomatic bone;
• Inferior wall - orbital surface of the body of the maxilla, orbital surface of the zygomatic bone, and orbital process of the palatine bone.