The eight muscles of the human tongue are classified as either intrinsic or extrinsic. The four intrinsic muscles act to change the shape of the tongue, and are not attached to any bone. The four extrinsic muscles act to change the position of the tongue, and are anchored to bone.
Extrinsic[edit]
The extrinsic muscles originate from bone and extend to the tongue. Their main functions are altering the tongue's position allowing for protrusion, retraction, and side-to-side movement.[3]
- Genioglossus, which arises from the mandible and protrudes the tongue. It is also known as the "safety muscle" of the tongue since it is the only muscle having the forward action.
- Hyoglossus, which arises from the hyoid bone and depresses the tongue
- Styloglossus, which arises from the styloid process of the temporal bone and elevates and retracts the tongue
- Palatoglossus, which arises from the palatine aponeurosis, and depresses the soft palate, moves the palatoglossal fold towards the midline, and elevates the back of the tongue.
Intrinsic[edit]
Four paired intrinsic muscles of the tongue originate and insert within the tongue, running along its length. These muscles alter the shape of the tongue by: lengthening and shortening it, curling and uncurling its apex and edges, and flattening and rounding its surface. This provides shape, and helps facilitate speech, swallowing, and eating.[3]
- The superior longitudinal muscle runs along the superior surface of the tongue under the mucous membrane, and elevates, assists in retraction of, or deviates the tip of the tongue. It originates near the epiglottis, the hyoid bone, from the median fibrous septum.
- The inferior longitudinal muscle lines the sides of the tongue, and is joined to the styloglossus muscle.
- The vertical muscle is located in the middle of the tongue, and joins the superior and inferior longitudinal muscles.
- The transverse muscle divides the tongue at the middle, and is attached to the mucous membranes that run along the sides.
Blood supply[edit]
The tongue receives its blood supply primarily from the lingual artery, a branch of the external carotid artery. The lingual veins, drain into the internal jugular vein. The floor of the mouth also receives its blood supply from the lingual artery.[3]There is also a secondary blood supply to the tongue from the tonsillar branch of the facial artery and the ascending pharyngeal artery.
An area in the neck sometimes called Pirogov's triangle is formed by the intermediate tendon of the digastric muscle, the posterior border of the mylohyoid muscle, and thehypoglossal nerve.[4][5] The lingual artery is a good place to stop severe hemorrage from the tongue.
Innervation[edit]
Innervation of the tongue consists of motor fibers, special sensory fibers for taste, and general sensory fibers for sensation.[3]
- Motor supply for all intrinsic and extrinsic muscles of the tongue is supplied by efferent motor nerve fibers from the hypoglossal nerve (CN XII), with the exception of thepalatoglossus. The palatoglossus is innervated by the vagus nerve (CN X).[3]
Innervation of taste and sensation is different for the anterior and posterior part of the tongue because they are derived from different embryological structures (pharyngeal arch1 and pharyngeal arch 3 and 4, respectively).[6]
- Anterior two thirds of tongue (anterior to the vallate papillae):
- Taste: chorda tympani branch of the facial nerve (CN VII) via special visceral afferent fibers
- Sensation: lingual branch of the mandibular division (V3) of the trigeminal nerve (CN V) via general somatic afferent fibers
- Posterior one third of tongue:
- Taste and sensation: glossopharyngeal nerve (CN IX) via a mixture of special and general visceral afferent fibers.
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