The accessory nerve
Accessory nerve (XI) · nervus accessorius
The eleventh cranial nerve, which powers your shrugging and head-turning muscles.
What it does
Unusually for a cranial nerve, the accessory nerve begins mostly in the upper spinal cord, climbs into the skull, then exits again. It supplies the sternocleidomastoid, which turns the head, and the trapezius, which shrugs the shoulders.
Surprising fact
It runs just under the skin across the side of the neck, so a simple biopsy of a lymph node there can accidentally injure it.
Why it matters
Doctors test it by asking you to shrug against their hands and turn your head against resistance.
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.