View source for Orbit (anatomy)

{{Infobox Anatomy |
  Name         = {{PAGENAME}} |
  Latin        = orbitae |
  GraySubject  = 46 |
  GrayPage     = 188 |
  Image        = Orbital_bones.png |
  Caption      = The seven bones which articulate to form the orbit.<BR>yellow = [[Frontal bone]]<BR>green = [[Lacrimal bone]]<BR>brown = [[Ethmoid bone]]<br>blue = [[Zygomatic bone]]<BR>purple = [[Maxillary bone]]<BR>aqua = [[Palatine bone]]<BR>red = [[Sphenoid bone]] |
  Image2       = |
  Caption2     = |
  System       = |
  Precursor    = |
  MeshName     = Orbit |
  MeshNumber   = A02.835.232.781.324.690 |
  DorlandsPre  = o_05 |
  DorlandsSuf  = 12594914 |
}}
{{CMG}}
__NOTOC__


==Overview==

In [[anatomy]], the '''orbital bone''' is the cavity or socket of the [[skull]] in which the [[eye]] and its [[adnexa|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. <ref> Duane's Ophthalmology, Chapter 32 ''Embryology and Anatomy of the Orbit and Lacrimal System''
. (eds Tasman W, Jaeger EA)
Lippincott/Williams & Wilkins, 2007 </ref>

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

The base, which opens in the face, has four borders. The 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 the orbital plate [[frontal bone]] and the lesser wing of [[sphenoid]]. The orbital surface presents medially by trochlear fovea and laterally by lacrimal fossa

The floor (inferior wall) is formed by the orbital surface of [[maxilla]], the orbital surface of [[zygomatic bone]] and the orbital process of [[palatine bone]]. Medially near the orbital margin is 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 fossa|pterygopalatine]] and [[infratemporal fossa]].

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

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

===Fat cushion===
In the orbit, surrounding the eyeball and its muscles, is a layer of fat that helps the eye rotate around a fixed center of rotation.  If excess liquid is collected in the fat cushion tissue, the eye may protrude.  <ref>"eye, human."Encyclopædia Britannica. 2008. Encyclopædia Britannica 2006 Ultimate Reference Suite DVD 5 Apr. 2008 </ref>

==Contents==
* Eyeball
* [[Fascia]]s: Orbital, [[Bulbar]]
* [[Muscles of orbit|Extraocular muscles]] ([[Levator Palpebrae Superioris]], Superior, Inferior, Lateral and Medial [[Rectus muscle]]s, Superior and Inferior Oblique Muscles)
* [[Nerve]]s: [[cranial nerve]]s [[optic nerve|II]], [[oculomotor nerve|III]], [[trochlear nerve|IV]], [[trigeminal nerve|V]], and [[abducens nerve|VI]]
* [[Blood vessel]]s
* Extraocular [[Fat]]
* [[Lacrimal gland]], [[Lacrimal sac]], [[Nasolacrimal duct]]
* [[Eyelids]]
* Medial and Lateral Palpebral ligaments
* Medial and Lateral Check ligaments
* [[Suspensory ligament]] of the eyeball
* [[Conjunctiva]]
* [[Trochlea]]
* [[Orbital septum]]
* [[Ciliary ganglion]] and short ciliary nerves

==Bones==

In [[humans]], seven bones make up the bony orbit:
* [[Frontal bone]] ([[Pars orbitalis]])
* [[Lacrimal bone]]
* [[Ethmoid bone]] ([[Lamina papyracea]])
* [[Zygomatic bone]] ([[Orbital process of the the zygomatic bone]])
* [[Maxillary bone]] ([[Orbital surface of the body of the maxilla]])
* [[Palatine bone]] ([[Orbital process of palatine bone]])
* [[Sphenoid bone]] ([[greater wing of sphenoid bone |Greater]] and [[lesser wing of sphenoid bone | lesser]] wings)

==Foramina and openings==
#[[Optic foramen]]
#[[Superior orbital fissure]]
#[[Inferior orbital fissure]]
#[[Anterior ethmoid foramen]]
#[[Posterior ethmoidal foramen]]
#[[Infraorbital foramen]]
#[[Supraorbital foramen]]
#[[Naso-lacrimal canal opening]]
#[[Zygomatic orbital foramen]]

==Additional images==
<gallery>
 Image:Gray190.png|The skull from the front.
 Image:Gray192.png|Medial wall of left orbit.
 Image:Gray787.png|Dissection showing origins of right ocular muscles, and nerves entering by the superior orbital fissure.
 Image:Gray859.png|Coronal section of nasal cavities.
 Image:Orbita mensch.jpg
 Image:Lateral orbit anatomy 2.jpg|Lateral orbit anatomy
 Image:Lateral orbit nerves.jpg|Lateral orbit nerves
</gallery>

==References==
<references/>

==External links==
* {{eMedicine|oph|2}} - "Arterial Supply, Orbit"
* {{SUNYAnatomyLabs|29|os|05|01}}
* {{UMichAtlas|eye_5}}
* {{UMichAtlas|rsa2p4}}
* [http://anatome.ncl.ac.uk/tutorials/eye/page3.html Interactive tutorial at anatome.ncl.ac.uk]
{{clr}}

{{Head general}}
[[Category:Ophthalmology]]
[[Category:Anatomy]]


<br>
[[de:Orbita]]
[[es:Órbita (anatomía)]]
[[fr:Orbite (anatomie)]]
[[it:Orbita oculare]]
[[la:Orbita (anatomia)]]
[[nl:Orbita]]
[[ja:眼窩]]
[[pl:Oczodół]]
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[[fi:Silmäkuoppa]]
[[sv:Ögonhåla]]


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