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Oculomotor nerve

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noun, plural: oculomotor nerves

The cranial nerve associated with motor innervation of upper eyelid muscle, extraocular muscle and pupillary muscle


Cranial nerves are paired nerves that emerge from the brain and the brainstem. They supply the motor pathways between organs in the face and the upper body, and account for detecting and processing various sensations. One of the cranial nerves is the oculomotor nerve, which is also referred to as the third cranial nerve or cranial nerve III (CN III). The oculomotor nerve is the pair of nerves responsible for motor innervation of upper eyelid muscle, extraocular muscle and pupillary muscle. It enables focus on near objects. The oculomotor nerve enters the orbit through the superior orbital fissure. It is derived from the basal plate of the embryonic midbrain. Lesions of the oculomotor nerve may result in ptosis or the dropping of eyelid. Deviation of the eyeball outward, double vision and a dilated pupil are also possible outcome due to damage to the oculomotor nerve.

This cranial nerve works together with the cranial nerve IV and the cranial nerve VI in controlling movements of the eyeballs.


  • cranial nerve III (CN III)
  • third cranial nerve

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