Orbit

Orbit is the skull's compartment containing the eyeball, extraocular muscles, lacrimal gland, ophthalmic blood vessels, and multiple cranial nerves. The medial and inferior wall of the orbit is particularly thin and fragile^* that may play an essential role in the compensatory "emergency" decompression of the orbit in case of direct eye trauma.

^* Brady S, et al. The diagnosis and management of orbital blowout fractures: update 2001. Am J Emerg Med, 2001;19(2):147-154.

Aditus orbitalis, or the opening to the orbit — Anterior opening to the right orbit. Frontal view.
The list of terms:
Aditus orbitalis – Orbital aditus (opening to the orbit)
Margo supraorbitalis (aditus orbitalis) – Supraorbital margin (of orbital aditus)
Margo medialis (aditus orbitalis) – Medial margin (of orbital aditus)
Margo infraorbitalis (aditus) – Infraorbital margin (of aditus)
Margo lateralis (aditus) – Lateral margin (of aditus)
Paries superior orbitae – Upper wall of orbit
Paries medialis orbitae – Medial wall of orbit
Paries inferior orbitae – Inferior wall of orbit
Paries lateralis orbitae – Lateral wall of orbit
Fissura orbitalis superior – Superior orbital fissure
Fissura orbitalis inferior – Inferior orbital fissure

Markup for lateral view of zygomatic bone — Medial wall of the orbit.
In terms of the skeleton, the medial wall of the orbit is the most complex one. Note the orbital process of palatine bone that forms a fraction of the wall, but is a useful anatomical landmark for endoscopic endonasal surgical approach to the orbit's medial wall^*.
The list of terms:
Processus frontalis maxillae – Frontal process of maxilla
Os lacrimale – Lacrimal bone
Lamina orbitalis ossis ethmoidalis – Orbital plate of ethmoid bone
Processus orbitalis ossis palatini – Orbital process of palatine bone
Corpus ossis sphenoidalis – Body of sphenoid bone
Foramen ethmoidale anterius – Anterior ethmoidal foramen
Foramen ethmoidale posterius – Posterior ethmoidal foramen
Canalis opticus – Optic canal

^* Gras-Cabrerizo J, Martel-Martin M, et al. Surgical anatomy of the medial wall of the orbit in 14 human cadavers. J Neurol Surg B Skull Base, 2016; 77(6):439–444.

Lateral wall of the orbit with the terminology comments — Lateral wall of the orbit.
The list of terms:
Facies orbitalis ossis zygomatici – Orbital surface of zygomatic bone
Facies orbitalis alae majoris ossis sphenoidalis – Orbital surface of the greater wing of sphenoid bone
Foramen zygomatico-orbitale – Zygomatico-orbital foramen
Fissura orbitalis superior – Superior orbital fissure
Fissura orbitalis inferior – Inferior orbital fissure

Upper wall of the orbit with the terminology comments — Upper wall of the orbit.
The list of terms:
Facies orbitalis ossis frontalis – Orbital surface of the frontal bone
Facies orbitalis alae minoris ossis sphenoidalis – Orbital surface of the lesser wing of sphenoid bone
Fossa glandulae lacrimalis – Fossa for lacrimal gland

Markup for the lower wall of the orbit — Lower wall of the orbit.
The list of terms:
Facies orbitalis ossis zygomatici – Orbital surface of zygomatic bone
Facies orbitalis maxillae – Orbital surface of maxilla
Hamulus lacrimalis – Lacrimal hamulus (hook)
Canalis nasolacrimalis – Nasolacrimal canal
Sulcus infraorbitalis – Infraorbital groove
Canalis infraorbitalis – Infraorbital canal
Fissura orbitalis inferior – Inferior orbital fissure

First published: Feb/2020
Last update: 18/Nov/2020