oculomotor nerve

References

oculomotor nerve

anatomy

Also known as: third cranial nerve

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Last updated

July 1, 2026

Quick Summary

The oculomotor nerve, also known as cranial nerve III, is crucial for eye movement and function. It originates in the midbrain and exits the skull through the superior orbital fissure to reach the eye socket.1

This nerve controls several key muscles:
* Superior, medial, and inferior recti muscles: These muscles move the eyeball up, in, and down, respectively.
* Inferior oblique muscle: This muscle rotates the eyeball upward and outward.
* Levator palpebrae superioris muscle: This muscle lifts the upper eyelid.
* Sphincter pupillae and ciliary muscles: These muscles control the iris to adjust pupil size and the lens for focusing.1

Damage to the oculomotor nerve can lead to drooping eyelids, an inability to move the eye in certain directions, and dilated pupils, resulting in double vision.12

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human nervous system
Oculomotor nerve (CN III or 3)
The oculomotor nerve arises from two nuclei in the rostral midbrain. These are (1) the oculomotor nucleus, the source of general somatic efferent fibers to superior, medial, and inferior recti muscles, to the inferior oblique muscle, and to the…
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The oculomotor nerve arises from two nuclei in the rostral midbrain. These are (1) the oculomotor nucleus, the source of general somatic efferent fibers to superior, medial, and inferior recti muscles, to the inferior oblique muscle, and to the…
Read More

nervous system disease
Oculomotor, trochlear, and abducens nerves
Compression of the oculomotor, trochlear, or abducens nerves may be caused by lesions, diabetes, vascular disease, head injury, infection, or neuropathy. In the brainstem, multiple sclerosis, stroke, Wernicke disease (see below Brainstem
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Compression of the oculomotor, trochlear, or abducens nerves may be caused by lesions, diabetes, vascular disease, head injury, infection, or neuropathy. In the brainstem, multiple sclerosis, stroke, Wernicke disease (see below Brainstem
Read More

nervous system disease
Cranial nerves
The physician tests the three oculomotor nerves (oculomotor, trochlear, and abducens) together by asking the patient to gaze in different directions on command and to follow a moving object with the eyes only. The shape, size, and reactivity of the pupils—both to light and to close objects—are also tested. The…
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The physician tests the three oculomotor nerves (oculomotor, trochlear, and abducens) together by asking the patient to gaze in different directions on command and to follow a moving object with the eyes only. The shape, size, and reactivity of the pupils—both to light and to close objects—are also tested. The…
Read More

human nervous system
Parasympathetic nervous system
The third cranial nerve (oculomotor nerve) contains parasympathetic nerve fibers that regulate the iris and lens of the eye. From their origin in the Edinger-Westphal nucleus of the midbrain, preganglionic axons travel to the orbit and synapse on the ciliary ganglion. The ciliary ganglion contains two types of postganglionic…
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The third cranial nerve (oculomotor nerve) contains parasympathetic nerve fibers that regulate the iris and lens of the eye. From their origin in the Edinger-Westphal nucleus of the midbrain, preganglionic axons travel to the orbit and synapse on the ciliary ganglion. The ciliary ganglion contains two types of postganglionic…
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human nervous system
Midbrain
…the nuclear complex of the oculomotor nerve as well as the trochlear nucleus; these cranial nerves innervate muscles that move the eye and control the shape of the lens and the diameter of the pupil. In addition, between the midbrain reticular formation (known here as the tegmentum) and the crus…
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…the nuclear complex of the oculomotor nerve as well as the trochlear nucleus; these cranial nerves innervate muscles that move the eye and control the shape of the lens and the diameter of the pupil. In addition, between the midbrain reticular formation (known here as the tegmentum) and the crus…
Read More