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Nerve: Hypoglossal nerve
Hypoglossal nerve, cervical plexus, and their branches.
Plan of hypoglossal nerve.
Latin N. Hypoglossus
Gray's subject #207 914
Innervates genioglossus, hyoglossus, styloglossus, thyrohyoid, omohyoid, sternothyroid and sternohyoid
To ansa cervicalis
MeSH A08.800.800.120.330

The hypoglossal nerve is the twelfth cranial nerve. The nerve arises from the hypoglossal nucleus and emerges from the medulla oblongata between the olive and the pyramids. It then passes through the hypoglossal canal. On emerging from the hypoglossal canal, the nerve picks up a branch from the anterior ramus of C1. It spirals behind the vagus nerve and passes between the internal carotid artery and internal jugular vein lying on the carotid sheath. After passing deep to the posterior belly of the digastric muscle, it passes to the tongue.

It supplies motor fibres to all of the muscles of the tongue, except the palatoglossus muscle which is innervated by the vagus nerve (X) and the accessory nerve (XI).

Aside from the tongue, the hypoglossal nerve also controls, via the ansa cervicalis, thyrohyoid muscle, omohyoid muscle, sternothyroid muscle and sternohyoid muscle. The nerve fibres supplying these muscles all come from the C1 contribution.

Testing the hypoglossal nerve

To test the function of the nerve, a person is asked to poke out their tongue. If there is a loss of function on one side (unilateral paralysis,) the tongue will point towards the affected side.

The strength of the tongue can be tested by getting the person to poke at the inside of their cheek, and feeling how strongly they can push a finger pushed against their cheek - a more elegant way of testing than directly touching the tongue.

The tongue can also be looked at for signs of lower motorneuron disease, such as fasciculation and atrophy.

Ipsilateral paralysis/pareisis of the tongue, results in contralateral curvature of the tongue (toward the unimpaired side of the mouth).

Additional images

External links

Major nerves (also see Peripheral nervous system)

Cranial nerves: I olfactory | II optic | III oculomotor | IV trochlear | V trigeminal | V1 ophthalmic (lacrimal, frontal, supratrochlear, supraorbital, nasociliary, ciliary ganglion) | V2 maxillary (sphenopalatine ganglion) | V3 mandibular (buccal - auriculotemporal - lingual - inferior alveolar - otic ganglion) | VI abducens | VII facial (chorda tympani, nervus intermedius) | VIII vestibulocochlear (cochlear, vestibular) | IX glossopharyngeal | X vagus (recurrent laryngeal, Alderman's nerve) | XI accessory | XII hypoglossal

Posterior spinal nerves: greater occipital

C1-C4 - Cervical plexus: lesser occipital | greater auricular | lesser auricular | phrenic | ansa cervicalis

C5-C8, T1 - Brachial plexus: supraclavicular branches (dorsal scapular, suprascapular, long thoracic) | lateral cord (musculocutaneous, lateral antibrachial cutaneous, lateral head of median nerve) | medial cord (ulnar, medial head of median nerve, medial antibrachial cutaneous, medial brachial cutaneous) | posterior cord (axillary, radial)

T2-T11: intercostal

T12, L1-L5 - Lumbar plexus: iliohypogastric | ilioinguinal | genitofemoral | lateral femoral cutaneous | femoral | obturator

S1-S4 - Sacral plexus: gluteal | posterior femoral cutaneous | tibial | sciatic | sural | common peroneal

S2-S5 - Pudendal plexus: perforating cutaneous | pudendal | visceral | muscular | anococcygeal

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