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The tongue is a muscular organ in the oral cavity that plays an important role in the digestive system and speech. The hypoglossal nerve, also known as the twelfth cranial nerve, innervates all the extrinsic and intrinsic muscles of the tongue except for the palatoglossus muscle, which is supplied by the vagus nerve. The hypoglossal nerve enables tongue movement and controls the hyoglossus, genioglossus, styloglossus, and intrinsic muscles. These muscles help with speaking, swallowing, and moving substances around in the mouth.
| Characteristics | Values |
|---|---|
| Nerve Name | Hypoglossal nerve |
| Synonyms | Cranial nerve X, CN X, CN XII, Twelfth cranial nerve |
| Muscle Controlled | Genioglossus, Hyoglossus, Styloglossus, Intrinsic muscles |
| Functions | Tongue movement, Speech, Swallowing, Clearing mouth of saliva |
| Sensory Information | Glossopharyngeal nerve (CN IX), Lingual nerve, Facial nerve (CN VII) |
| Risk of Injury | High during carotid endarterectomy |
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What You'll Learn
The hypoglossal nerve enables tongue movement
The hypoglossal nerve, also known as the twelfth cranial nerve, cranial nerve XII, or simply CN XII, is a nerve with a sole motor function. It controls tongue movement, allowing us to speak, swallow, and move substances around in our mouths.
The hypoglossal nerve innervates all the extrinsic and intrinsic muscles of the tongue, except for the palatoglossus, which is supplied by the vagus nerve. The nerve originates from the hypoglossal nucleus in the medulla as several small rootlets, which pass through the hypoglossal canal and down through the neck. The nerve then passes up again over the tongue muscles it supplies into the tongue. The nerve is involved in controlling tongue movements required for speech and swallowing, including sticking out the tongue and moving it from side to side.
The hypoglossal nerve controls the hyoglossus, genioglossus, styloglossus, and intrinsic muscles. The genioglossus muscles push the tongue forward, the hyoglossus muscles pull the tongue back and flatten it, and the intrinsic muscles change the shape of the tongue, including curving and narrowing it. The styloglossus muscles move the tongue up and down.
The hypoglossal nerve is at high risk of injury during carotid endarterectomy. Certain health conditions can affect the hypoglossal nerve's function, including sleep apnea, stroke, and trauma. If the nerve is injured, the tongue may appear to have the appearance of a "bag of worms" or wasting.
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The lingual nerve provides sensory innervation
The tongue is a muscular organ of the oral cavity that plays an important role in mastication, taste, swallowing, speech, and clearing the oral cavity. The lingual nerve provides sensory innervation to the anterior two-thirds of the tongue, carrying general sensory information about temperature and touch. This nerve is a branch of the mandibular nerve (CN V3) or the trigeminal nerve (CN V), which is one of the cranial nerves. The lingual nerve collects sensory information from the tongue's surface and transmits it to the central nervous system.
The lingual nerve is an important component of the tongue's neurovascular supply, which also includes arteries, veins, and other nerves. The arterial supply to the tongue primarily comes from the lingual artery, a branch of the external carotid artery, with additional contributions from the tonsillar branch of the facial artery. The venous drainage of the tongue is handled by the lingual vein, which empties into the internal jugular vein. Understanding the embryological development of the tongue helps elucidate its complex innervation.
The hypoglossal nerve (CN XII), a cranial nerve, innervates all the intrinsic muscles and all but one of the extrinsic muscles of the tongue. The exception is the palatoglossus muscle, which receives motor innervation from the vagus nerve (CN X). The hypoglossal nerve enables tongue movement and plays a crucial role in speech, swallowing, and moving substances around in the mouth. It originates from the hypoglossal nucleus in the medulla and travels down the neck, branching out to innervate the tongue muscles.
The glossopharyngeal nerve (CN IX) provides sensory innervation to the posterior one-third of the tongue, carrying general sensory information from the mucosa and special sensory information from the vallate papillae. It exits the skull through the jugular foramen and descends down the lateral surface of the stylopharyngeus muscle. The vagus nerve (CN X) also plays a role in tongue innervation, supplying the palatoglossus muscle indirectly through branches of the pharyngeal plexus.
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The vagus nerve innervates the palatoglossus muscle
The vagus nerve, also known as Cranial Nerve X (CN X), is a functionally diverse nerve that provides innervation to the palatoglossus muscle of the tongue. It is the only muscle of the tongue innervated by the vagus nerve. The vagus nerve carries general sensory information from the mucosa of the posterior third of the tongue and special sensory information from the vallate papillae.
The vagus nerve offers a wide range of modalities of innervation, including motor, sensory, and autonomic functions. It provides motor innervation to the majority of the muscles in the pharynx, soft palate, and larynx. The vagus nerve also provides sensory information to the skin of the external acoustic meatus and the internal surfaces of the laryngopharynx and larynx.
The vagus nerve plays a crucial role in swallowing and phonation by mediating the functions of the palatoglossus muscle. The palatoglossus muscle is associated with the soft palate and helps elevate the posterior portion of the tongue. It arises from the palatine aponeurosis and inserts itself broadly along the tongue.
The vagus nerve also has visceral functions, providing visceral sensation to the heart and abdominal viscera. It regulates heart rhythm and innervates the smooth muscle of the trachea, bronchi, and gastrointestinal tract. The vagus nerve is the main parasympathetic outflow to the heart and gastrointestinal organs in the thorax and abdomen.
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The glossopharyngeal nerve carries sensory information
The tongue is a muscular organ in the oral cavity that plays an important role in the digestive system and speech. The hypoglossal nerve, also known as the twelfth cranial nerve, cranial nerve XII, or CN XII, innervates all the tongue muscles except the palatoglossus. The hypoglossal nerve enables tongue movement and controls the hyoglossus, genioglossus, styloglossus, and intrinsic muscles. These muscles help with speaking, swallowing, and moving substances around in the mouth.
The hypoglossal nerve is a general somatic efferent (GSE) type nerve that provides motor control of the extrinsic muscles of the tongue. It originates from the hypoglossal nucleus in the medulla and travels down the neck, branching out and ending at the base and underside of the tongue. The nerve passes through the hypoglossal canal in the skull's occipital bone and reforms, descending through the neck to the angle of the mandible. It then travels underneath the tongue to innervate the tongue muscles.
The hypoglossal nerve is at high risk of injury during certain procedures, such as carotid endarterectomy. Damage to the nerve can affect the appearance and movement of the tongue, leading to potential issues with speaking, chewing, and swallowing.
Now, focusing on the glossopharyngeal nerve: The glossopharyngeal nerve (CN IX) carries sensory information from the posterior one-third of the tongue. It provides both general sensory information from the mucosa and special sensory information from the vallate papillae. The glossopharyngeal nerve exits the skull through the jugular foramen and descends down the lateral surface of the stylopharyngeus muscle. It then passes through the oropharyngeal triangle, supplying sensory information to the mucosa and vallate papillae.
In summary, the hypoglossal nerve innervates and controls most tongue muscles, while the glossopharyngeal nerve (CN IX) carries sensory information from the posterior third of the tongue.
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The hypoglossal nerve is at high risk of injury
The hypoglossal nerve is the 12th cranial nerve and is responsible for enabling tongue movement. It controls the hyoglossus, intrinsic, genioglossus, and styloglossus muscles, which help with speaking, swallowing, and moving substances around in the mouth.
To minimise the risk of injury, it is crucial to have a good understanding of the nerve's anatomy and course. The hypoglossal nerve originates from the medulla and travels caudally and dorsally to the tongue. It passes through the hypoglossal canal in the skull's occipital bone and extends upward as the neck develops. The nerve innervates all the intrinsic muscles and all but one of the tongue's extrinsic muscles.
The potential consequences of hypoglossal nerve injury include difficulties with eating, speaking, and swallowing. Isolated hypoglossal loss may be addressed with swallowing and articulatory therapy, but combined with other nerve deficits, it can significantly impact functional loss and rehabilitation.
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Frequently asked questions
The hypoglossal nerve innervates all the tongue muscles except for the palatoglossus muscle.
The hypoglossal nerve provides motor control of the extrinsic muscles of the tongue, including the genioglossus, hyoglossus, and styloglossus muscles. It also controls the intrinsic muscles of the tongue.
The hypoglossal nerve originates from the hypoglossal nucleus in the medulla as small rootlets, passing through the hypoglossal canal and down through the neck.
Damage to the hypoglossal nerve can affect the appearance and movement of the tongue, leading to issues with speech, swallowing, and chewing.
The palatoglossus muscle is innervated by the vagus nerve and is associated with the soft palate.
