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Bones of the Orbit

The bony orbit is the skeletal cavity which is made up of several cranial structures and surrounds the soft tissue that make up the eye.

Its function is to provide a stable and enclosed environment for the eyeball and its adjacent structures. 

Bony orbit (Superior orbital fissure highlighted in green) - ventral view

Bony orbit (Superior orbital fissure highlighted in green) - ventral view

Although it may appear to be a spherical cavern, the bony orbit is actually more like a canal. It has a large opening anteriorly in the upper face, where the part of the eye that is used directly to see emerges from and two smaller fissures and a canal posteriorly, that connect the inner cranium with the exterior part of the skull, allow several anatomical structures to pass through them.

Firstly, the individual bones that make up the bony orbit will be discussed, along with how they connect to one another. Secondly, the anatomical landmarks and fissures of the bones, including those made due to their articulations (between bones) will also be described in detail, especially those which have structures passing through them. Lastly, in the final paragraph, the most important pathological disorder will be mentioned.

Bones & Walls of the Orbit

Anterior Wall

In a clockwise direction (using the right orbit, which is on the reader’s left side), the bones that contribute to the anterior margin and anterior walls of the bony orbit include the frontal bone, which provides the anterior superior rim of the orbit and the majority of the ceiling of the orbital cavern.

Frontal bone - ventral view

Frontal bone - ventral view

Next is the maxilla, which contributes via the frontal and nasal portions of its entire mass to the anterior medial margin and anterior inferior medial margin of the rim of the orbit, as well as the majority of the floor of the bony orbit.

Maxilla - ventral view

Maxilla - ventral view

The last bone in rotation that contributes to the anterior lateral internal and external walls of the bony orbit is the zygoma or the facial portion of the zygomatic bone.

Zygomatic bone - ventral view

Zygomatic bone - ventral view

Internal Medial Wall

The internal medial wall continues posteriorly and superiorly from the maxilla up to the frontal bone and consists of first the lacrimal bone and just behind it, the vertical plate of the ethmoid bone.

Lacrimal bone - ventral view

Lacrimal bone - ventral view

The posterior margin of the ethmoid plate articulates with the greater and lesser wings of the sphenoid bone, as does the maxilla inferiorly (but only with the greater wing).

Posterior Wall

The sphenoid bone forms the entire posterior wall of the bony orbit. A tiny slither of the vertical plate of the palatine bone, known as the orbital process can be seen between the maxilla, the ethmoid bone and the sphenoid bone.

Sphenoid bone - ventral view

Sphenoid bone - ventral view

Articulations of the Orbit

Inside the orbit the articulations are not openly named and are not expected as common knowledge from medical students in an exam. For now, only the main sutures that are mentioned in the anatomy books will be listed here. As previously mentioned, the order will be clockwise using the right orbit for reference:

  • The frontomaxillary suture articulates the frontal bone and the maxilla in the superior anterior margin of the orbital rim
  • The zygomaticomaxillary suture can be seen just lateral of the infraorbital foramen and has a lateral diagonal stance. it links the maxilla to the facial portion of the zygomatic bone
  • The frontozygomatic suture joins the most superior aspect of the zygoma to the frontal bone on the superior lateral margin of the anterior orbital opening.

Frontozygomatic suture - axial view

Frontozygomatic suture - axial view

Anatomical Landmarks & Fissures

External Foramina

The anatomical landmarks of the orbit consist of the three external and six internal openings, with the actual eye socket opening not being counted due to it’s size.

Supraorbital foramen - ventral view

Supraorbital foramen - ventral view

The three external landmarks are foramina:

  • the supraorbital foramen on the superior margin of the orbital rim in the frontal bone
  • the infraorbital foramen on the inferior margin of the orbital rim in the maxilla
  • the zygomaticofacial foramen slightly more lateral to the latter, in the facial portion of the zygomatic bone

These foramina contain the superior and inferior orbital nerves and vessels and the zygomaticofacial nerve and vessels respectively.

Infraorbital foramen - ventral view

Infraorbital foramen - ventral view

Internal Foramina

The six internal openings are situated on the posterior and medial walls of the orbit. The posterior openings are bordered by the greater and lesser wings of the sphenoid bone and the ethmoid bone. The inferior orbital fissure is an exception and has only the greater wing of the sphenoid bone and the maxilla as an opposing border, rather than the ethmoid bone. The superior and inferior orbital fissures and the optic canal are the landmarks currently under review.

Recommended video: Nerves of the orbit
Nerves found on the region of the orbit.

The optic canal is much smaller than the other two landmarks and is considered the most superior of the three. It contains:

Optic canal - ventral view

Optic canal - ventral view

The next below the latter is the superior orbital fissure, which is the second largest of the fissures, however it holds the most content, including:

Superior orbital fissure - ventral view

Superior orbital fissure - ventral view

Lastly, the inferior orbital fissure which is the largest and most inferior structure in the posterior wall of the bony orbit, contains:

Inferior orbital fissure - ventral view

Inferior orbital fissure - ventral view

The medial wall landmarks include the nasolacrimal canal and fossa, which can be seen on the most anterior aspect of the lacrimal bone at its border with the maxilla. It holds the lacrimal sac which continues on as the nasolacrimal duct.

The final structures are the anterior and posterior ethmoidal foramina, which sit in the suture between the ethmoid bone and the frontal bone and contain the anterior and posterior ethmoidal nerves and vessels respectively.

Anterior and posterior ethmoidal foramina - ventral view

Anterior and posterior ethmoidal foramina - ventral view

Clinical Aspects

One of the most severe fractures that include the bony orbit is the blow out fracture. This is when the floor of the bony orbit, namely the maxilla caves in as a result of a combination of facial fractures such as the Le Fort II or III and zygomatic fractures. Clinically, the condition presents with:

  • decreased visual acuity in the affected eye
  • periorbital ecchymosis and edema
  • pupillary dysfunction
  • pain
  • ocular misalignment
  • hypo- or hypertropia
  • a step in the inferior margin upon palpation

Treatment includes reconstructing the orbital floor and stabilizing the bones that surround and contribute to its formation.

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Show references

References:

  • Neil S. Norton, Ph.D. and Frank H. Netter, MD, Netter’s Head and Neck Anatomy for Dentistry, 2nd Edition, Elsevier Saunders, Chapter 2 Osteology, Page 42, 47, 55, 61, 482 and 483.
  • Adam J Cohen, MD and Deepak Narayan, MD, FRCS (March 6, 2012). Orbital floor fractures(Blowout).

Author:

  • Dr. Alexandra Sierosławska

Illustrators:

  • Bony orbit (Superior orbital fissure highlighted in green) - ventral view - Paul Kim
  • Frontal bone - ventral view - Paul Kim 
  • Maxilla - ventral view - Paul Kim
  • Zygomatic bone - ventral view - Paul Kim
  • Lacrimal bone - ventral view - Paul Kim
  • Sphenoid bone - ventral view - Yousun Koh
  • Supraorbital foramen - ventral view - Paul Kim
  • Optic canal - ventral view - Paul Kim
  • Infraorbital foramen - ventral view - Paul Kim
  • Superior orbital fissure - ventral view - Paul Kim
  • Inferior orbital fissure - ventral view - Paul Kim
  • Anterior and posterior ethmoidal foramina - ventral view - Paul Kim
© Unless stated otherwise, all content, including illustrations are exclusive property of Kenhub GmbH, and are protected by German and international copyright laws. All rights reserved.

Related Atlas Images

Bones of the orbit

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Nerves of the orbit

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