View source for Oculomotor nerve

{{Infobox Nerve |
  Name         = Oculomotor nerve |
  Latin        = nervus oculomotorius |
  GraySubject  = 198 |
  GrayPage     = 884 |
  Image        = Gray776.png |
  Caption      = Nerves of the orbit. Seen from above. |
  Image2       = |
  Caption2     = |
  Innervates   = [[Superior rectus]], [[Inferior rectus]], [[Medial rectus]], [[Inferior oblique]], [[Ciliary muscle|Ciliary]] |
  BranchFrom   = [[oculomotor nucleus]], [[Edinger-Westphal nucleus]] |
  BranchTo     = [[Superior branch of oculomotor nerve|superior branch]], [[Inferior branch of oculomotor nerve|inferior branch]] |
  MeshName     = Oculomotor+Nerve |
  MeshNumber   = A08.800.800.120.600 |
}}
{{CMG}}



==Overview==

The '''oculomotor nerve''' is the third of twelve paired [[cranial nerves]]. It controls most of the [[eye movement]]s (cranial nerves [[trochlear|IV]] and [[abducens|VI]] also do some), constriction of the pupil, and holding the eyelid open.

==Pathophysiology==

See [[Oculomotor nerve palsy]].

===Nuclei===
The oculomotor nerve arises from the anterior aspect of [[mesencephalon]] (midbrain). There are two nuclei for the oculomotor nerve:

* The [[oculomotor nucleus]] originates at the level of the [[superior colliculus]]. The muscles it controls are the [[ciliary muscle]] (affecting [[Accommodation reflex|accommodation]]), and all [[extraocular muscles]] except for the [[superior oblique muscle]] and the [[lateral rectus muscle]]. 

* The [[Edinger-Westphal nucleus]] supplies [[parasympathetic]] fibres to the eye via the [[ciliary ganglion]], and thus controls [[pupil constriction]].

===Emergence from brain===
On emerging from the brain, the nerve is invested with a sheath of [[pia mater]], and enclosed in a prolongation from the [[arachnoid mater|arachnoid]]. 

It passes between the [[superior cerebellar]] (below) and [[posterior cerebral]] arteries (above), and then pierces the dura mater in front of and lateral to the [[posterior clinoid process]], passing between the free and attached borders of the [[tentorium cerebelli]]. 

It runs along the lateral wall of the [[cavernous sinus]], above the other [[orbital nerve]]s, receiving in its course one or two filaments from the [[cavernous plexus]] of the sympathetic, and a communicating branch from the [[ophthalmic division]] of the [[trigeminal]].

===Superior and inferior rami===
It then divides into two branches, which enter the orbit through the superior orbital fissure, between the two heads of the [[lateral rectus]]. 

Here the nerve is placed below the [[trochlear nerve]] and the frontal and lacrimal branches of the ophthalmic nerve, while the [[nasociliary nerve]] is placed between its two rami:

* [[superior branch of oculomotor nerve]]
* [[inferior branch of oculomotor nerve]]

==Testing the oculomotor nerve==
===[[Eye muscles]]===
Cranial nerves III, IV and VI are usually tested together. The examiner typically instructs the patient to hold his head still and follow only with the eyes a finger or penlight that circumscribes a large "H" in front of the patient. By observing the [[eye movements]] and [[eyelid]]s, the examiner is able to obtain more information about the [[extraocular muscles]], the [[levator palpebrae superioris muscle]], and cranial nerves III, IV, and VI.

Since the oculomotor nerve controls most of the eye muscles, it may be easier to detect damage to it.  Damage to this nerve, termed '''[[oculomotor nerve palsy]]''' is also known by the '''down n' out''' symptoms, because of the position of the affected eye.

===[[Pupillary reflex]]===
The oculomotor nerve also controls the constriction of the [[pupil]]s. This can be tested in two main ways. By moving a finger towards a person's face to induce [[accommodation reflex|accommodation]], as well as them going cross-eyed, their pupils should constrict.

Shining a light into their eyes should also make their pupils constrict. Both pupils should constrict at the same time, independent of what eye the light is actually shone on.

==Additional images==
<gallery>
 Image:Gray567.png|Dura mater and its processes exposed by removing part of the right half of the skull, and the brain.
 Image:Gray569.png|Tentorium cerebelli from above.
 Image:Gray710.png|Coronal section through mid-brain.
 Image:Gray715.png|Mesal aspect of a brain sectioned in the median sagittal plane.
 Image:Gray719.png|Hind- and mid-brains; postero-lateral view.
 Image:Gray720.png|Median sagittal section of brain. 
 Image:Gray745.png|Dissection showing the course of the cerebrospinal fibers.
 Image:Gray775.png|Plan of oculomotor nerve. 
 Image:Gray777.png|Nerves of the [[orbit (anatomy)|orbit]], and the [[ciliary ganglion]]. Side view. 
 Image:Gray779.png|Alveolar branches of superior maxillary nerve and sphenopalatine ganglion.
 Image:Gray785.png|Figure showing the mode of innervation of the Recti medialis and lateralis of the eye.
 Image:Gray786.png|Oblique section through the right cavernous sinus.
 Image:Gray787.png|Dissection showing origins of right ocular muscles, and nerves entering by the superior orbital fissure.
 Image:Ciliary ganglion pathways.png|Pathways in the Ciliary Ganglion.
</gallery>

== See also ==
* [[Anisocoria]]
* [[Oculomotor nucleus]]

==External links==
* {{LoyolaMedEd|GrossAnatomy/h_n/cn/cn1/cn3.htm}}
* {{eMedicine|oph|183}} - "Oculomotor nerve palsy"
* {{MeshName|Oculomotor+Nerve}}
* {{BrainInfo|hier|479}}
* {{NormanAnatomy|cranialnerves}} ({{NormanAnatomyFig|III}})

{{Cranial nerves}}

[[Category:Peripheral nervous system]]
[[Category:Cranial nerves]]
[[Category:Neuroanatomy]]



[[de:Nervus oculomotorius]]
[[lt:Judinamasis akies nervas]]
[[nl:Nervus oculomotorius]]
[[ja:動眼神経]]
[[no:Nervus oculomotorius]]
[[pl:Nerw okoruchowy]]
[[pt:Nervo oculomotor]]
[[fi:Silmän liikehermo]]
[[zh:动眼神经]]


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