Cranial nerve · one in each half of the brain
Hypoglossal nerve (XII)
Also called Cranial nerve XII, CN XII, Twelfth nerve
The tongue's movement nerve, for talking, chewing, swallowing, and sticking it out.
The hypoglossal nerve moves your tongue. Your tongue is a bundle of muscles that is always busy: shaping words, pushing food between your teeth, and sweeping it back to swallow. This nerve sends the commands for nearly all of those moves. Each side controls its own half of the tongue.
Where it is
It leaves the front of the medulla, exits the skull through its own small canal, and curves forward under the jaw to enter the tongue from below.
What it does
Speaking
It shapes sounds like "t", "d", "l", and "n", which need the tongue to tap or press the roof of the mouth.
Chewing
It keeps food moving between your teeth so every bite gets chewed.
Swallowing
It pushes food and drink to the back of the mouth to start a swallow.
Keeping the airway open
It keeps the tongue from falling back and blocking the throat, especially during sleep.
Think of it as the joystick cable for your tongue, carrying every twist, curl, and push command from the brainstem.
Works with
- Medulla oblongataIts control center sits in the medulla, close to the centers for swallowing and breathing.
- Primary motor cortexThe tongue area of the motor cortex sends the commands for deliberate tongue moves.
- Broca's areaThis speech-planning area works out the tongue movements needed for each word.
- Vagus nerve (X)The tongue and throat work as a team to swallow and speak, with the vagus handling the throat and voice box.
- Motor neuronIts fibers are the long cables of motor neurons that make the tongue muscles contract.
When it goes wrong
How doctors check it
"Stick out your tongue and move it side to side." If one side is weak, the tongue points toward the weak side, because the healthy side pushes harder.
Nerve damage
Damage makes speech slurred and eating clumsy. Over time the weak half of the tongue can shrink and show fine twitching, which can be a sign of motor neuron disease (ALS).
Help for sleep apnea
For some people with sleep apnea, a small implant gently stimulates this nerve during sleep, nudging the tongue forward so air can keep flowing.
For learning only, not medical advice. If you have a health concern, talk to a doctor.
Surprising facts
- Your tongue has no bones. All its shape changes come from muscle fibers running in different directions: lengthwise, crosswise, and up and down.
- Tongue rolling is often said to be a simple inherited trait, but studies of identical twins show it is not that simple: one twin can sometimes do it while the other cannot.
By the numbers
Where the name comes from
From the Greek hypo, "under", and glossa, "tongue". It runs underneath the tongue to reach its muscles.
Quick quiz
3 questions. Your answers are saved and come back in your daily review.
Which of these is a job of the hypoglossal nerve (XII)?
Show the answer
Speaking. It shapes sounds like "t", "d", "l", and "n", which need the tongue to tap or press the roof of the mouth.
Speaking. It shapes sounds like "t", "d", "l", and "n", which need the tongue to tap or press the roof of the mouth.
The hypoglossal nerve (XII) is part of which larger structure?
Show the answer
Cranial nerves. It belongs to the cranial nerves.
Cranial nerves. It belongs to the cranial nerves.
Which part fits this description? "Like the joystick cable for your tongue, carrying every twist, curl, and push command from the brainstem."
Show the answer
Hypoglossal nerve (XII). It is the hypoglossal nerve (XII). The tongue's movement nerve, for talking, chewing, swallowing, and sticking it out.
Hypoglossal nerve (XII). It is the hypoglossal nerve (XII). The tongue's movement nerve, for talking, chewing, swallowing, and sticking it out.
These parts now come back in your daily review, just before you would forget them.
Practice it and its neighbors in 3DSources
- Neuroanatomy, Cranial Nerve 12 (Hypoglossal), StatPearls, NCBI Bookshelf
- Amyotrophic lateral sclerosis (ALS), MedlinePlus, National Library of Medicine
- Myths of Human Genetics: Tongue Rolling, John H. McDonald, University of Delaware
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