Structure and Origin
- The oculomotor nerve originates from the third nerve nucleus at the level of the superior colliculus in the midbrain.
- The fibers from the third nerve nuclei located laterally on either side of the cerebral aqueduct pass through the red nucleus.
- From the red nucleus, fibers pass via the substantia nigra to emerge from the substance of the brainstem at the oculomotor sulcus.
- The nerve is invested with a sheath of pia mater and enclosed in a prolongation from the arachnoid.
- It passes between the superior cerebellar and posterior cerebral arteries and then pierces the dura mater.

Branches
- The superior branch of the oculomotor nerve passes medially over the optic nerve.
- It supplies the superior rectus and levator palpebrae superioris.
- The inferior branch of the oculomotor nerve divides into three branches.
- One passes beneath the optic nerve to the medial rectus.
- Another branch goes to the inferior rectus.
- The third and longest branch runs forward between the inferior recti and lateralis to the inferior oblique.
- A short thick branch is given off to the lower part of the ciliary ganglion.

Nuclei
- The oculomotor nerve arises from the anterior aspect of the mesencephalon (midbrain).
- There are two nuclei for the oculomotor nerve: the oculomotor nucleus and the Edinger-Westphal nucleus.
- The oculomotor nucleus controls the striated muscle in levator palpebrae superioris and other extraocular muscles.
- The Edinger-Westphal nucleus supplies parasympathetic fibers to the eye via the ciliary ganglion, controlling pupil constriction and accommodation.
- Sympathetic postganglionic fibers also join the nerve from the plexus on the internal carotid artery.

Function
- The oculomotor nerve includes axons that innervate skeletal muscles responsible for eye movements.
- It innervates the levator palpebrae superioris, superior rectus, medial rectus, inferior rectus, and inferior oblique muscles.
- The nerve also provides preganglionic parasympathetics to the ciliary ganglion, controlling the constrictor pupillae and ciliary muscles.
- Axons of type GSE (general somatic efferent) and GVE (general visceral efferent) are present in the oculomotor nerve.
- Cranial nerves IV and VI also participate in the control of eye movement.

Additional Information
- Additional images related to the oculomotor nerve.
- Related topics such as anatomical terminology, anisocoria, cranial nerves, and the oculomotor nucleus.
- References and external links for further reading and verification of information.