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{{BioPsy}}
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{{Infobox Nerve |
 
{{Infobox Nerve |
Name = {{PAGENAME}} |
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Name = Oculomotor nerve |
Latin = N. Oculomotorius |
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Latin = nervus oculomotorius |
 
GraySubject = 198 |
 
GraySubject = 198 |
 
GrayPage = 884 |
 
GrayPage = 884 |
Image = Gray777.png |
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Image = Gray776.png |
Caption = Nerves of the [[orbit (anatomy)|orbit]], and the [[ciliary ganglion]]. Side view. |
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Caption = Nerves of the orbit. Seen from above. |
Innervates = [[Superior rectus]], [[Inferior rectus]], [[Medial rectus]], [[Inferior oblique]], [[Ciliary muscle|Ciliary]] |
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Image2 = |
Image2 = Gray775.png |
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Caption2 = |
Caption2 = Plan of oculomotor nerve. |
 
Width = 350 |
 
 
Innervates = [[Superior rectus]], [[Inferior rectus]], [[Medial rectus]], [[Inferior oblique]], [[Ciliary muscle|Ciliary]] |
 
Innervates = [[Superior rectus]], [[Inferior rectus]], [[Medial rectus]], [[Inferior oblique]], [[Ciliary muscle|Ciliary]] |
BranchFrom = |
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BranchFrom = [[oculomotor nucleus]], [[Edinger-Westphal nucleus]] |
BranchTo = |
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BranchTo = [[Superior branch of oculomotor nerve|superior branch]], [[Inferior branch of oculomotor nerve|inferior branch]] |
 
MeshName = Oculomotor+Nerve |
 
MeshName = Oculomotor+Nerve |
 
MeshNumber = A08.800.800.120.600 |
 
MeshNumber = A08.800.800.120.600 |
 
}}
 
}}
The '''oculomotor nerve''' is the third of twelve paired [[cranial nerves]]. It controls most of the [[eye movement]]s (cranical nerves IV and VI also do some), constriction of the pupil, and holding the eyelid open.
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The '''oculomotor nerve''' is the third of twelve paired [[cranial nerves]]. It controls most of the eye's movements, constriction of the pupil, and maintains an open eyelid. (Note: cranial nerves [[trochlear|IV]] and [[abducens|VI]] also participate in control of [[eye movement]].)
   
The oculomotor nerve arises from the anterior aspect of [[mesencephalon]] (midbrain). 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]]. In addition, it supplies [[parasympathetic]] fibres - which originate in the [[Edinger-Westphal nucleus]] - to the eye via the [[ciliary ganglion]], and thus controls [[pupil constriction]].
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==Path==
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===Nuclei===
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The oculomotor nerve arises from the anterior aspect of [[mesencephalon]] (midbrain). There are two nuclei for the oculomotor nerve:
   
==Anatomy of the oculomotor nerve==
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* 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]].
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 and posterior cerebral arteries, 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 nerves, 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. It then divides into two branches, which enter the orbit through the superior orbital fissure, between the two heads of the [[Rectus lateralis]]. 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.
 
   
The superior ramus, the smaller, passes medialward over the [[optic nerve]], and supplies the [[Rectus superior]] and [[Levator palpebræ superioris]]. The inferior ramus, the larger, divides into three branches. One passes beneath the optic nerve to the [[Rectus medialis]]; another, to the [[Rectus inferior]]; the third and longest runs forward between the Recti inferior and lateralis to the [[Obliquus inferior]]. From the last a short thick branch is given off to the lower part of the [[ciliary ganglion]], and forms its short root. All these branches enter the muscles on their ocular surfaces, with the exception of the nerve to the Obliquus inferior, which enters the muscle at its posterior border.
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* The [[Edinger-Westphal nucleus]] supplies [[parasympathetic]] fibres to the eye via the [[ciliary ganglion]], and thus controls [[pupil constriction]].
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===Emergence from brain===
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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]].
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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]].
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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]].
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===Superior and inferior rami===
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It then divides into two branches, which enter the orbit through the superior orbital fissure, between the two heads of the [[lateral rectus]].
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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:
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* [[superior branch of oculomotor nerve]]
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* [[inferior branch of oculomotor nerve]]
   
 
==Testing the oculomotor nerve==
 
==Testing the oculomotor nerve==
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===[[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.
 
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 controls most of the eye muscles, it may be easier to detect damage to it. Damage to this nerve, termed '''oculomotor nerve palsy''' is known by the '''down n' out''' symptoms. The affected eye will be looking downward, because the [[superior oblique muscle|superior oblique]] (innervated by CN IV), is unantagonized by the paralyzed [[superior rectus muscle|superior rectus]] and [[inferior oblique muscle|inferior oblique]] and looking outwards, because the [[lateral rectus muscle|lateral rectus]] (innervated by CN VI) is unantagonized by the paralyzed [[medial rectus muscle|medial rectus]]. There will also be [[strabismus]].
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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.
 
They may show a degree of [[ptosis]], or drooping of the eyelid, because the levator palpebrae superioris muscle (eyelid lifting muscle) is also innervated by the oculomotor nerve.
 
   
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===[[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.
 
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.
 
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.
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==Additional images==
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<gallery>
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Image:Gray567.png|Dura mater and its processes exposed by removing part of the right half of the skull, and the brain.
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Image:Gray569.png|Tentorium cerebelli from above.
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Image:Gray710.png|Coronal section through mid-brain.
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Image:Gray715.png|Mesal aspect of a brain sectioned in the median sagittal plane.
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Image:Gray719.png|Hind- and mid-brains; postero-lateral view.
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Image:Gray720.png|Median sagittal section of brain.
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Image:Gray745.png|Dissection showing the course of the cerebrospinal fibers.
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Image:Gray775.png|Plan of oculomotor nerve.
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Image:Gray777.png|Nerves of the [[orbit (anatomy)|orbit]], and the [[ciliary ganglion]]. Side view.
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Image:Gray779.png|Alveolar branches of superior maxillary nerve and sphenopalatine ganglion.
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Image:Gray785.png|Figure showing the mode of innervation of the Recti medialis and lateralis of the eye.
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Image:Gray786.png|Oblique section through the right cavernous sinus.
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Image:Gray787.png|Dissection showing origins of right ocular muscles, and nerves entering by the superior orbital fissure.
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Image:Ciliary ganglion pathways.png|Pathways in the Ciliary Ganglion.
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</gallery>
   
 
== See also ==
 
== See also ==
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==External links==
 
==External links==
* [http://www.meddean.luc.edu/lumen/MedEd/GrossAnatomy/h_n/cn/cn1/cn3.htm Loyola]
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* {{LoyolaMedEd|GrossAnatomy/h_n/cn/cn1/cn3.htm}}
 
* {{eMedicine|oph|183}} - "Oculomotor nerve palsy"
 
* {{eMedicine|oph|183}} - "Oculomotor nerve palsy"
 
* {{MeshName|Oculomotor+Nerve}}
 
* {{MeshName|Oculomotor+Nerve}}
 
* {{BrainInfo|hier|479}}
 
* {{BrainInfo|hier|479}}
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* {{NormanAnatomy|cranialnerves}} ({{NormanAnatomyFig|III}})
   
{{Nerves}}
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{{Cranial nerves}}
   
 
[[Category:Peripheral nervous system]]
 
[[Category:Peripheral nervous system]]
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[[Category:Neuroanatomy]]
 
[[Category:Neuroanatomy]]
   
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[[lt:Judinamasis akies nervas]]
[[ja:動眼神経]]
 
 
[[nl:Nervus oculomotorius]]
 
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{{enWP|Oculomotor nerve}}
 
{{enWP|Oculomotor nerve}}

Latest revision as of 23:39, March 24, 2008

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Nerve: Oculomotor nerve
Gray776
Nerves of the orbit. Seen from above.
[[Image:|250px|center|]]
Latin nervus oculomotorius
Gray's subject #198 884
Innervates Superior rectus, Inferior rectus, Medial rectus, Inferior oblique, Ciliary
From oculomotor nucleus, Edinger-Westphal nucleus
To superior branch, inferior branch
MeSH A08.800.800.120.600

The oculomotor nerve is the third of twelve paired cranial nerves. It controls most of the eye's movements, constriction of the pupil, and maintains an open eyelid. (Note: cranial nerves IV and VI also participate in control of eye movement.)

PathEdit

NucleiEdit

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

Emergence from brainEdit

On emerging from the brain, the nerve is invested with a sheath of pia mater, and enclosed in a prolongation from the 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 nerves, 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 ramiEdit

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:

Testing the oculomotor nerveEdit

Eye musclesEdit

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 eyelids, 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 reflexEdit

The oculomotor nerve also controls the constriction of the pupils. This can be tested in two main ways. By moving a finger towards a person's face to induce 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 imagesEdit

See also Edit

External linksEdit

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