Oculomotor Nerve
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Original Editor - Innocent Abugu
Top Contributors - Innocent Abugu, Uchechukwu Chukwuemeka, Kim Jackson, Vidya Acharya and Joseph Ayotunde Aderonmu
Description[edit | edit source]
The oculomotor nerve is the third cranial nerve (CNIII). It has somatic motor (general somatic efferent) and visceral motor (general visceral efferent-parasympathetic) functions.[1]
Root[edit | edit source]
It originates from the oculomotor nucleus and the Edinger-Westphal nucleuswithin the midbrain of the brainstem.
Branches[edit | edit source]
Superior branch innervates the superior rectus and the levator palpabraesuperioris
Inferior branch innervates the medial rectus, inferior rectus and inferior oblique.
Function[edit | edit source]
Motor[edit | edit source]
The oculomotor nerve is the chief motor nerve to the ocular and extraocular muscles. (clinical oriented anatomy)
The oculomotor nerves send somatic motorfibres to all extraocular muscles, except the superior oblique and lateral rectus. The superior branch supplies the superior rectus which elevates the eyeball, and the levatorpalpabraesuperioris which raises the upper eyelid.
The inferior branch innervates the medial rectus adducts the eyeball, the inferior rectus which depresses the eyeball and the inferior oblique which elevates, abducts and laterally rotates the eyeball. The superior oblique and the lateral rectus are supplied by the trochlear and abducens nerves respectively.
Parasympathetic[edit | edit source]
There are two primary functions of the autonomic parasympathetic (involuntary) oculomotor nerve. It constricts the pupil (miosis) by innervating the smooth muscle (sphincter pupillae) near the pupil. It also innervates the ciliary muscles. (Neuroanatomy, Cranial Nerve 3 (Oculomotor)
Joyce C, Le PH, Peterson DC.) The ciliary muscle changes the shape of the lens duringaccomodation.
Sympathetic[edit | edit source]
The oculomotor nerve has no direct function, but sympathetic fibres run with the oculomotor nerve to innervate the superior tarsal muscle (helps to raise the eyelid). (Teach me anatomy)
Clinical relevance[edit | edit source]
Damage to the oculomotor nerve or any of its branches could lead to oculomotor motor nerve palsy (Third nerve palsy) Some of the causes include:
· Vascular ischemia
· Trauma
· Intracranial neoplasm
· Hemorrhage
· Congenital
· Idiopathic (Cranial Nerve III Palsy
Modi P, Arsiwalla T.)
Assessment[edit | edit source]
Treatment[edit | edit source]
Resources[edit | edit source]
References[edit | edit source]
- ↑ Keith LM, Arthur FD, Anne MR. Clinically Oriented Anatomy.
