Summary
Summary The Oculomotor Nerve (CN III)
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This is a summary of the anatomy and functions associated with the Oculomotor Nerve (CN III)
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The Oculomotor Nerve (CN III) The oculomotor nerve carries somatic motor axons that innervate the
extraocular muscles responsible for eye movement
It also carries preganglionic parasympathetic neurones that control the
smooth muscle within the eye itself (sphincter pupillae and ciliary muscles)
Anatomical course:
The oculomotor nerve arises from the anterior part of the midbrain
It proceeds anteriorly, passing below the posterior cerebral artery and above
the superior cerebellar artery
It pierces that dura and enters the lateral aspect of the cavernous sinus,
before travelling with sympathetic fibres from the internal carotid plexus
These fibres don’t join the oculomotor nerve, they simply travel within the
same sheath
The nerve leaves the cranial cavity and enters the orbit via the superior
orbital fissure
From here it divides into a superior and inferior branch, each branch
innervates different structures within the orbit:
- Superior branch: provides motor innervation to the superior rectus and
levator palpabrae superioris muscles, while sympathetic fibres run with
this branch to innervate the superior tarsal muscle
- Inferior branch: provides motor innervation to the inferior rectus, medial
rectus and inferior oblique muscles. Parasympathetic fibres travel to the
ciliary ganglion, which go onto innervate the sphincter pupillae and ciliary
muscles in the eye
Motor function:
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