Oculomotor nerves

Oculomotor nerve is the third cranial nerve. It is responsible for the majority of the eye's movements and for the constriction of the pupil and maintaining an open eyelid. The nerve originates from the midbrain.

Anatomy

The oculomotor nerve is derived from the basal plate of the embryonic midbrain. Cranial nerves IV and VI also participate in control of eye movement.

Nuclei

The oculomotor nerve originates from the oculomotor nucleus in the midbrain. The nucleus is located in the midline, at the level of the superior colliculus. The muscles it controls are derived from the basal plate of the embryonic midbrain.

Function

The oculomotor nerve innervates all the extraocular muscles except for the superior oblique muscle and the lateral rectus muscle. It also innervates the levator palpebrae superioris, which lifts the eyelid. The nerve also contains parasympathetic fibers, which innervate the sphincter pupillae, leading to constriction of the pupil, and the ciliary muscle, which controls lens shape.

Clinical significance

Damage to the oculomotor nerve can result in double vision and the inability to coordinate the movements of both eyes (strabismus), and ptosis, or drooping of the eyelid. Damage to this nerve may also result in an inability to open the eye due to paralysis of the levator palpebrae muscle.

See also

• Cranial nerves
• Eye movement
• Pupil

References

Oculomotor nerves Resources
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