Orbit (anatomy)

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Template:Infobox Anatomy In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated.

It can also mean the skin which surrounds the eye of a bird.

In the adult human, the volume of the orbit is 30 ml, of which the eye occupies 6.5 ml. ^[1]

1 Definition
2 Contents
3 Bones
4 Foramina and openings
5 Additional images
6 References
7 External links

Definition

The orbits are conical cavities, which open into midline of the face. Each consists of a base, an apex and four walls.

The base, which opens in the face, has four borders that following bones take part in their formation:

1. Superior margin: frontal bone
2. Inferior margin: maxilla and zygomatic
3. Medial margin: frontal, lacrimal and maxilla
4. Lateral margin: zygomatic and frontal

The apex lies near the medial end of superior orbital fissure and contain the optic canal which communicates with middle cranial fossa.

The roof (superior wall) is formed by orbital plate frontal bone and lesser wing of sphenoid. The orbital surface presents medially by trochlear fovea and laterally by lacrimal fossa

The floor (inferior wall) is formed by orbital surface of maxilla, orbital surface of zygomatic bone and orbital process of palatine bone. Medially near the orbital margin located the groove for nasolacrimal duct. Near the middle of the floor, located infraorbital groove, which leads to the infraorbital foramen. The floor is separated from the lateral wall by inferior orbital fissure, which connects the orbit to pterygopalatine and infartemporal fossa.

The medial wall is formed by frontal process of maxilla, lacrimal bone, orbital plate of ethmoid and a small part of body of sphenoid.

The Lateral wall is formed by orbital process of zygomatic and orbital plate of greater wing of sphenoid. The bones meet at zygomaticosphenoid suture. The lateral wall is the thickest wall of the orbit.

                                                                                            By:F.Monshizadeh

Eyeball
Fascias: Orbital, Bulbar
Extraocular muscles
Nerves: cranial nerves II, III, IV, V, and VI
Blood vessels
Fat
Lacrimal gland

Bones

In humans, seven bones make up the bony orbit:

Foramina and openings

Additional images

Gray190.png The skull from the front.	Gray192.png Medial wall of left orbit.	Gray787.png Dissection showing origins of right ocular muscles, and nerves entering by the superior orbital fissure.	Gray859.png Coronal section of nasal cavities.
Orbita mensch.jpg	Lateral orbit anatomy 2.jpg Lateral orbit anatomy	Lateral orbit nerves.jpg Lateral orbit nerves	Massospondylus Skull Steveoc 86.png The orbit in relation to the other skull openings in the dinosaur Massospondylus.

References

^ Duane's Ophthalmology, Chapter 32 Embryology and Anatomy of the Orbit and Lacrimal System . (eds Tasman W, Jaeger EA) Lippincott/Williams & Wilkins, 2007