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What is the origin and course of Oculomotor nerve?
Oculomotor nerve is the 3rd cranial nerve. It Is purely motor nerve.
Origin: Its nuclei lie in midbrain at the level of superior colliculus.
Course
- It emerges from the ventral aspect of midbrain (in the interpeduncular fossa) between posterior cerebral and superior cerebellar arteries.
- Runs forward in the lateral wall of the cavernous sinus.
- Dives into two divisions– superior and inferior.
- Passes through the central part of superior orbital fissure to enter the orbit.
Name the nuclei, functional components and structures supplied by oculomotor nerve .
Following are the nuclei, functional components and the structures supplied by these:
| Nuclei | Functional component | Structures innervated |
|---|---|---|
| Oculomotor nucleus (in midbrain) | GSE (General Somatic Efferent) | Supplies following extraocular muscles: Superior rectus, Inferior rectus, Medial rectus, Inferior oblique and Levator palpabrae superioris |
| Edinger Westphal nucleus (in midbrain) | GVE( General Visceral Efferent) | Sphincter papillae and ciliaris muscles |
Applied Aspects
Lesion of oculomotor nerve
The symptoms are:
- Lateral strabismus/squint: due to paralysis of medial rectus and unopposed action of lateral rectus muscle.
- Ptosis/drooping of upper eyelid: due to paralysis of levator palpebrae superioris.
- Dilated pupil: paralysis of sphincter papillae.
- Loss of accommodation: due to paralysis of medial rectus, sphincter papillae and ciliaris muscles.
- Diplopia on looking medially and superiorly.
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