The hypoglossal nerve (cranial nerve XII) leaves the front of the medulla oblongata as a row of small rootlets in the anterolateral sulcus, the groove between the pyramid and the olive. [1]
The 3D brain needs JavaScript. The text below still says where the hypoglossal nerve is and what it does.
Opens cut by a side (sagittal) slice through the medulla oblongata, which the hypoglossal nerve leaves the brain from. Drag to turn, pinch or scroll to zoom, tap any part to name it; .
It crosses the subarachnoid space, leaves the skull through the hypoglossal canal in the occipital bone, beside the foramen magnum, then runs down the neck between the internal carotid artery and the internal jugular vein and forward under the jaw into the tongue. [1]
Not a separate shape in this atlas; lit: the part it leaves the brain from. Lit: the whole medulla oblongata, the part the hypoglossal nerve leaves the brain from. The nerve itself, which runs on to the tongue, has no shape in the BodyParts3D model, so nothing is drawn for it at a guessed point. [2][1]
Where it leaves the brain: the medulla oblongata. Its rootlets come out of the front of the medulla in the anterolateral sulcus between the pyramid and the olive, further forward than the glossopharyngeal, vagus and accessory rootlets behind the olive. [1][3]
Lit here: the medulla oblongata, the part the hypoglossal nerve leaves the brain from — see it on its own page.
Next to it, each lit on its own page: vagus nerve.
Where it is
Its cell bodies sit in the hypoglossal nucleus, near the bottom of the brainstem in the medulla. [1]
Below the skull it gives off a meningeal branch, picks up fibres from the first cervical spinal nerve (C1), spirals down behind the vagus nerve and runs between the internal carotid artery and the internal jugular vein. [1]
At the level of the angle of the jaw it comes out from behind the back belly of the digastric muscle, loops round a branch of the occipital artery and runs forward beneath the jaw, along the hyoglossus muscle, to the genioglossus and on towards the tip of the tongue. [1]
What it does
It is purely motor. It works the tongue’s own (intrinsic) muscles and three of the four muscles that move it from outside: the genioglossus, hyoglossus and styloglossus. The fourth, the palatoglossus, is worked by the vagus nerve. [1][4]
These muscles shape and move the tongue for speech, chewing and swallowing; the two genioglossus muscles stick it out, each pushing it towards the opposite side, so together they push it straight. [1]
The hypoglossal nucleus gets input from the motor cortex of both hemispheres, but the input from the opposite side is the stronger one. [1]
Connections
Two branches made of the C1 fibres it carries leave it in the neck: the thyrohyoid branch to the thyrohyoid muscle and the geniohyoid branch to the geniohyoid muscle. [1]
The hypoglossal nucleus is linked with the reticular formation, which takes part in automatic movements of the tongue such as clearing saliva from the mouth. [1]
Other names
Cranial nerve XII (CN XII), twelfth cranial nerve; nervus hypoglossus (Latin). The name means “under the tongue”, from the Greek hypo (under) and glossa (tongue), after its path below the tongue. Herophilos first described it in the 3rd century BC; Winslow first used the name hypoglossal in 1733. [1]
Size
The model has no shape for the hypoglossal nerve, so it is not measured here. The medulla oblongata, lit as the part it leaves the brain from, measures about 33 mm front to back, 41 mm top to bottom and 27 mm side to side on this model (the box it fits in, not its volume). [2]
Facts describe anatomy and normal function only. The 3D model is the adult male BodyParts3D brain (credits and licence); real brains vary in size and shape, so its measurements describe one model, not anyone’s brain.