Bony Anatomy of the Orbit
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Dimensions of the Orbit
The orbit is a pyramidal shaped structure, with the base of the pyramid forming the orbital rim.[1] The walls of the orbit angle posteriorly towards the optic canal to form the orbital apex.
The average dimensions of the orbit are as follows:[2]
| Average dimensions | |
|---|---|
| Volume | 30ccs |
| Height | 35mm |
| Width | 40mm |
| Length of the medial orbital wall | 45mm |
| Length of the lateral orbital wall | 35mm |
Bones of the Orbital Rim
The orbital rim is formed by three bones: the frontal, zygomatic, and maxillary bones.[3] The orbital rim is strong compared to the relatively weak orbital walls and helps provide protection for the globe.
The frontal bone forms the superior rim and contains the supraorbital foramen/notch, through which the supraorbital nerve, artery, and vein pass.
The zygomatic bone contributes to the lateral, inferior, and medial rim and contains the zygomaticotemporal foramen and the zygomaticofacial foramen.
The maxillary bone forms the inferior rim and contains the infraorbital foramen, through which the infraorbital nerve, artery, and vein pass.
Bones of the Orbital Wall
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The orbit is made of four orbital walls, and a total of seven bones. [1][2][3]
| 1. | Frontal bone |
| 2 . | Sphenoid bone (lesser and greater wing) |
| 3. | Zygomatic bone |
| 4. | Maxillary bone |
| 5. | Palatine bone |
| 6. | Ethmoid bone |
| 7. | Lacrimal bone |
| Orbital Wall | Number of Bones | Bones |
|---|---|---|
| Orbital Roof | 2 | Frontal bone
Lesser wing of the sphenoid |
| Lateral Wall | 2 | Zygomatic bone
Greater wing of the sphenoid |
| Orbital Floor | 3 | Zygomatic bone
Maxillary bone Palatine bone |
| Medial Wall | 4 | Palatine bone
Ethmoid bone Lacrimal bone Sphenoid bone |
Orbital Roof
The orbital roof is made of two bones: the frontal bone and the lesser wing of the sphenoid. The frontal bone separates the orbit from the anterior cranial fossa.
The frontal bone also contains three important foramen and fossa.[1]
- The supraorbital notch or foramen is located on the medial third of the portion of the frontal bone that comprises the superior orbital rim.
- The fossa of the lacrimal gland is located on the inferior surface of the frontal bone underneath the zygomatic process and houses the lacrimal gland in the superolateral orbit.
- Superomedially, a shallow depression creates the trochlear fossa, which houses the complex trochlear apparatus.
See Orbital Roof Fractures for more on orbital injuries associated with the orbital roof.
Lateral Wall
Two bones comprise the lateral orbital wall: the zygomatic bone and the greater wing of the sphenoid.[1] The lateral orbital wall is the strongest wall of the orbit.
Whitnall’s tubercle, also known as the lateral orbital tubercle, is a bony prominence on the zygomatic bone that serves as an important anatomic landmark on the lateral orbital wall.[4] The tubercle is located 11 mm inferior to the frontozygomatic suture and 4-5mm posterior to the lateral orbital rim.[4]
Whitnall’s tubercle serves as the attachment site for several important structures including:[4][5][6]
| Lockwood's ligament |
| Lateral canthal tendon |
| Lateral horn of the levator aponeurosis |
| Lateral rectus check ligament |
| Lacrimal gland fascia |
| Lateral extremities of the superior and inferior tarsal plates |
Whitnall’s tubercle is an important surgical anatomic landmark as it often serves as the location for reattachment during lateral canthal procedures, such as a lateral tarsal strip. Proper attachment at this site is indicated to prevent the development of eyelid malposition such as entropion or ectropion. In the absence of Whitnall’s tubercle, the height of the lateral orbital wall (as determined by the maximum distance of the zygomaticofrontal suture to the jugal point) has been proposed to reliably localize the lateral canthal insertion site.[7]
Of note, Whitnall’s ligament does not attach at Whitnall’s tubercle. Rather, Whitnall’s ligament forms septa through the lacrimal gland fascia with fibers inserted onto the lateral orbital wall several millimeters above Whitnall’s tubercle.[8]
Orbital Floor
Three bones make up the orbital floor: the maxillary bone, zygomatic bone, and palatine bone.[2][3] The orbital floor separates the orbit from the underlying maxillary sinus. Orbital floor fractures are the most common orbital fractures. The origin of the inferior oblique muscle also lies within the orbital floor posterior to the inferior medial orbital rim. Care must be taken to separate this muscle out during orbital floor fracture repairs to prevent iatrogenic damage.
Medial Wall
The medial wall is formed by four bones. Anteriorly to posteriorly, they are the maxillary bone, lacrimal bone, ethmoid bone, and the sphenoid bone.[3] The ethmoid bone contains the lamina papyracea, which makes up the bulk of the medial orbital wall and is often involved in medial wall fractures due to its paper-thin qualities. Interruption of the lamina papyracea can allow for the spread of infection from the ethmoid sinus.
Orbital Foramina, Fissures, and Canals
The optic foramen is located in the lesser wing of the sphenoid bone. It extends into the orbit, traveling in an inferior, anterior, and lateral direction. The optic nerve, the ophthalmic artery, and the choroid plexus all pass through the optic foramen as they enter the orbit.[2]
The supraorbital foramen is a small opening at the superior and medial margin of the orbit in the frontal bone. It is called the supraorbital notch if the foramen is incomplete. It contains the supraorbital nerve, artery, and vein. The supraorbital nerve is a sensory branch of the frontal nerve, which branches from the ophthalmic division of the trigeminal nerve (CN V1), and provides sensory cutaneous innervation to the forehead, upper eyelid, and root of the nose.[9]
The superior orbital fissure is located between the greater and lesser wings of the sphenoid bone. Cranial nerves III, V, IV, and VI all travel within the superior orbital fissure. The common tendinous ring surrounds the optic canal and the lower half of the superior orbital fissure. It is also the origin of the four recti muscles. [3]
Above the common tendinous ring, the superior orbital fissure transmits the lacrimal and frontal branches of CN V1, CN IV, and the superior ophthalmic vein. The superior and inferior divisions of CN III, the nasociliary branch of CN V1, sympathetic fibers of CN V1, and sympathetic fibers to the ciliary ganglion all pass through this fissure.[1]
The inferior orbital fissure is located on the floor of the orbit. The infraorbital nerve, zygomatic nerve, and inferior ophthalmic vein traverse this fissure.
The inferior orbital canal is located within the maxilla and eventually leads anteriorly to the infraorbital foramen below the inferior orbital rim.[3] The infraorbital foramen transmits the infraorbital nerve, artery, and vein. The infraorbital nerve provides sensory cutaneous innervation to the lower eyelid, anterior cheek, side of the nose, and upper lip.[9]
The zygomaticotemporal foramen and the zygomaticofacial foramen are small openings located within the zygomatic bone on the orbital rim.[9] [10] [11] Both the zygomaticotemporal foramen and zygomaticofacial foramen contain their respective named nerves, which are terminal branches of the maxillary division of the trigeminal nerve (CN V2). The zygomaticotemporal nerve gives sensory innervation to the skin on the temporal forehead and parasympathetic innervation to the lacrimal gland. The zygomaticofacial nerve provides cutaneous sensory innervation to the prominence of the cheek.
| Structure | Location | Contents | Nerve | Supplies |
|---|---|---|---|---|
| Optic foramen | Lesser wing of the sphenoid | Optic nerve
Ophthalmic artery Choroid plexus |
Optic nerve | Retina |
| Supraorbital foramen | Frontal bone | Supraorbital nerve, artery, and vein | Supraorbital nerve | Sensory cutaneous innervation to the forehead, upper eyelid, and root of the nose |
| Zygomaticotemporal foramen | Zygomatic bone | Zygomaticotemporal nerve | Zygomaticotemporal nerve | Sensory cutaneous innervation to the temporal forehead
Parasympathetic innervation to the lacrimal gland |
| Zygomaticofacial foramen | Zygomatic bone | Zygomaticofacial nerve | Zygomaticofacial nerve | Sensory cutaneous innervation to the prominence of the cheek |
| Superior orbital fissure | Between the greater and lesser wing of the sphenoid bone | Oculomotor nerve (CN III)
Trochlear nerve (CN IV) Ophthalmic division of the trigeminal nerve (CN V1) Abducens nerve (CN VI) Superior ophthalmic vein (SOV) |
Oculomotor nerve (CN III)
Trochlear nerve (CN IV) Ophthalmic division of the trigeminal nerve (CN V1) Abducens nerve (CN VI) Superior ophthalmic vein (SOV) |
|
| Inferior orbital fissure | Greater wing of the sphenoid, maxilla, palatine bone, and zygomatic bone | Infraorbital nerve
Infraorbital artery Infraorbital vein Zygomatic nerve Inferior ophthalmic vein (IOV) |
Infraorbital nerve
Infraorbital artery Infraorbital vein Zygomatic nerve Inferior ophthalmic vein (IOV) |
|
| Inferior orbital canal
Infraorbital foramen |
Maxillary bone | Infraorbital nerve, artery, and vein | Infraorbital nerve | Sensory cutaneous innervation to the lower eyelid, anterior cheek, side of the nose, and upper lip |
- ↑ 1.0 1.1 1.2 1.3 1.4 René C. Update on orbital anatomy. Eye (Lond). 2006;20(10):1119-1129.
- ↑ 2.0 2.1 2.2 2.3 Shumway CL, Motlagh M, Wade M. Anatomy, Head and Neck, Orbit Bones. In: StatPearls. Treasure Island (FL): StatPearls Publishing; July 24, 2023.
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 Nerad, Jeffrey A. Techniques in Ophthalmic Plastic Surgery : A Personal Tutorial. Philadelphia: Saunders Elsevier, 2010. Print.
- ↑ 4.0 4.1 4.2 Whitnall SE. On a Tubercle on the Malar Bone, and on the Lateral Attachments of the Tarsal Plates. J Anat Physiol. 1911;45(Pt 4):426-432.
- ↑ Gray’s Anatomy, 39th Edition: The Anatomical Basis of Clinical Practice. AJNR Am J Neuroradiol. 2005;26(10):2703-2704.
- ↑ Fillmore EP, Seifert MF. Chapter 22 - Anatomy of the Trigeminal Nerve. In: Tubbs RS, Rizk E, Shoja MM, Loukas M, Barbaro N, Spinner RJ, eds. Nerves and Nerve Injuries. Academic Press, 2015: 319-350.
- ↑ Loukas M, Owens DG, Tubbs RS, Spentzouris G, Elochukwu A, Jordan R. Zygomaticofacial, zygomaticoorbital and zygomaticotemporal foramina: anatomical study. Anat Sci Int. 2008;83(2):77-82.
- ↑ Lim HW, Paik DJ, Lee YJ. A cadaveric anatomical study of the levator aponeurosis and Whitnall's ligament. Korean J Ophthalmol. 2009;23(3):183-187.
- ↑ 9.0 9.1 9.2 Gray’s Anatomy, 39th Edition: The Anatomical Basis of Clinical Practice. AJNR Am J Neuroradiol. 2005;26(10):2703-2704.
- ↑ Fillmore EP, Seifert MF. Chapter 22 - Anatomy of the Trigeminal Nerve. In: Tubbs RS, Rizk E, Shoja MM, Loukas M, Barbaro N, Spinner RJ, eds. Nerves and Nerve Injuries. Academic Press, 2015: 319-350.
- ↑ Loukas M, Owens DG, Tubbs RS, Spentzouris G, Elochukwu A, Jordan R. Zygomaticofacial, zygomaticoorbital and zygomaticotemporal foramina: anatomical study. Anat Sci Int. 2008;83(2):77-82.
