The oculomotor nerve
Oculomotor nerve (III) · nervus oculomotorius
The third cranial nerve, which moves most of your eye muscles, lifts your eyelid and narrows your pupil.
What it does
The oculomotor nerve leaves the front of the midbrain and travels to the eye socket. It powers four of the six muscles that move the eye, lifts the upper lid, and carries fibres that narrow the pupil and help the lens focus on near objects.
Surprising fact
When this nerve stops working, the eye turns down and out, the eyelid droops, and the pupil stays wide open.
Why it matters
A suddenly enlarged pupil that won't react to light can be a warning sign of pressure inside the skull, which is why doctors check pupils after a head injury.
Nearby
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Sources
Drafted with AI help; awaiting a human fact-check against these sources.
Open in the 3D atlas · Suggest a correction · Not medical advice.
3D models: Z-Anatomy & BodyParts3D (CC BY-SA 4.0 / 2.1 JP). Card text CC BY 4.0.