Third cranial nerve

Third Cranial Nerve

The third cranial nerve, also known as the oculomotor nerve, as illustrated in Gray's Anatomy.

The Third Cranial Nerve or Oculomotor Nerve is one of the twelve cranial nerves that originate from the brain. It is responsible for the majority of the eye's movements and for the constriction of the pupil and accommodation.

Anatomy

The oculomotor nerve originates in the midbrain, at the level of the superior colliculus. It travels through the cavernous sinus and enters the orbit via the superior orbital fissure.

Function

The oculomotor nerve innervates all the extraocular muscles except for the lateral rectus muscle (innervated by the abducens nerve) and the superior oblique muscle (innervated by the trochlear nerve). It also provides parasympathetic innervation to the pupil and the ciliary muscle.

Clinical significance

Damage to the oculomotor nerve can result in oculomotor nerve palsy, which can cause double vision, inability to coordinate the movements of both eyes (strabismus), and drooping of the eyelid (ptosis).

See also

• Cranial nerves
• Oculomotor nerve palsy
• Pupil
• Ciliary muscle