Tongue

For other uses, see Tongue (disambiguation).

Tongue
The human tongue
Latin	lingua
Gray's	subject #242 1125
Vein	lingual
Nerve	Anterior 2/3: lingual nerve & chorda tympani Posterior 1/3: Glossopharyngeal nerve (IX)
Precursor	pharyngeal arches, lateral lingual swelling, tuberculum impar
MeSH	Tongue
Dorlands/Elsevier	Tongue

The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste (gustation), as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly supplied with nerves and blood vessels. In humans a secondary function of the tongue is phonetic articulation. The tongue also serves as a natural means of cleaning one's teeth. The ability to perceive different tastes is not localised in different parts of the tongue, as is widely believed. This error arose because of misinterpretation of some 19th-century research (see tongue map).

Etymology

The word tongue derives from the Old English tunge, which comes from Proto-Germanic *tungōn. It has cognates in other Germanic languages — for example tonge in West Frisian, tong in Dutch/Afrikaans, tunge in Danish/Norwegian and tunga in Icelandic/Faroese/Swedish. The ue ending of the word seems to be a fourteenth-century attempt to show "proper pronunciation", but it is "neither etymological nor phonetic". Some used the spelling tunge and tonge as late as the sixteenth century.

It can be used as a metonym for language, as in the phrase mother tongue. Many languages have the same word for "tongue" and "language".

Figures of speech

A common temporary failure in word retrieval from memory is referred to as the tip-of-the-tongue phenomenon. The expression tongue in cheek refers to a statement that is not to be taken entirely seriously – something said or done with subtle ironic or sarcastic humour. A tongue twister is a phrase made specifically to be very difficult to pronounce. Aside from being a medical condition, "tongue-tied" means being unable to say what you want to due to confusion or restriction. The phrase "cat got your tongue" refers to when a person is speechless. To "bite one's tongue" is a phrase which describes holding back an opinion to avoid causing offence. A "slip of the tongue" refers to an unintentional utterance, such as a Freudian slip. Speaking in tongues is a common phrase used to describe glossolalia, which is to make smooth, language-resembling sounds that is no true spoken language itself. A deceptive person is said to have a forked tongue, and a smooth-talking person said to have a silver tongue.

Description

The human tongue

The underside of a human tongue

Musculature

Main article: Muscles of tongue

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 muscles

1. Genioglossus
2. Hyoglossus
3. Styloglossus
4. Palatoglossus

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.

Intrinsic muscles

1. Superior longitudinal
2. Inferior longitudinal
3. Verticalis
4. Transversus

The main function of the intrinsic muscles is to provide shape. They are not involved with changing the position of the tongue and are not attached to bone.

Vasculature

The tongue receives its blood supply primarily from the lingual artery, a branch of the external carotid artery and lingual veins which drain into internal jugular vein. The floor of the mouth also receives its blood supply from the lingual artery. The triangle formed by the intermediate tendon of the digastric muscle, the posterior border of the mylohyoid muscle, and the hypoglossal nerve is sometimes called Pirogov's, Pirogoff's, or Pirogov-Belclard's triangle. The lingual artery is a good place to stop severe hemorrage from the tongue.

There is also secondary blood supply to the tongue from the tonsillar branch of the facial artery and the ascending pharyngeal artery.

Innervation

Anterior 2/3rds of tongue

• General somatic afferent: lingual nerve branch of V3 of the trigeminal nerve CN V
• Taste: chorda tympani branch of facial nerve CN VII (carried to the tongue by the lingual nerve).

Posterior 1/3rd of tongue

• General somatic afferent and taste: Glossopharyngeal nerve CN IX

Motor

• All intrinsic and extrinsic muscles of the tongue are supplied by the hypoglossal nerve (CN XII), except for one of the extrinsic muscles, palatoglossus, which is innervated by the Vagus nerve CN X of the pharyngeal plexus.

Length

The average length of the human tongue from the oropharynx to the tip is 10 cm (4 in).

Physiology

Chemicals that stimulate taste receptor cells are known as tastants. Once a tastant is dissolved in saliva, it can make contact with the plasma membrane of the gustatory hairs, which are the sites of taste transduction.

The tongue is equipped with many taste buds on its dorsal surface, and each taste bud is equipped with taste receptor cells that can sense particular classes of tastes. There are taste cells for: sweet, bitter, salty or sour, and umami. Umami receptor cells are the least understood but research into the key features is making progress.

Pathology

Main article: Tongue disease

After the gums, the tongue is the second most common soft tissue site for various pathologies in the oral cavity. Pathological conditions of the tongue include geographic tongue, burning mouth syndrome, tongue necrosis, oral hairy leukoplakia, granular cell tumor and squamous cell carcinoma. Owing to optimal conditions of humidity, temperature and hiding niche between the tongue papillae and inside the pierced tongue, the tongue is a preferred site for colonization of Candida albicans.

Many infections are often found on or under the tongue. One rare but very possible infection is gonorrhea, characterized by small white bumps located underneath the tongue.

Sublingual medication

The sublingual region underneath the front of the tongue is a location where the oral mucosa is very thin, and underlain by a plexus of veins. This is an ideal location for introducing certain medications to the body. The sublingual route takes advantage of the highly vascular quality of the oral cavity, and allows for the speedy application of medication into the cardiovascular system, bypassing the gastrointestinal tract. This is the only convenient and efficacious route of administration (apart from I.V. administration) of nitroglycerin to a patient suffering chest pain from angina pectoris.

Non-human tongues

An okapi cleaning its muzzle with its tongue

Most vertebrate animals have tongues. In mammals such as dogs and cats, the tongue is often used to clean the fur and body. The tongues of these species have a very rough texture which allows them to remove oils and parasites. A dog's tongue also acts as a heat regulator. As a dog increases its exercise the tongue will increase in size due to greater blood flow. The tongue hangs out of the dog's mouth and the moisture on the tongue will work to cool the bloodflow.

Some animals have tongues that are specially adapted for catching prey. For example, chameleons, frogs, and anteaters have prehensile tongues.

Many species of fish have small folds at the base of their mouths that might informally be called tongues, but they lack a muscular structure like the true tongues found in most tetrapods.

Other animals may have organs that are analogous to tongues, such as a butterfly's proboscis or a radula on a mollusc, but these are not homologous with the tongues found in vertebrates, and often have little resemblance in function, for example, butterflies do not lick with their proboscides; they suck thorough them, and the proboscis is not a single organ, but two jaws held together to form a tube.

Macroglossum: View of the proboscis extended, which inspired the name of the animal. Literally the long tongue

As food

See also: Beef tongue

The tongues of some animals are consumed and sometimes considered delicacies. Hot tongue sandwiches are frequently found on menus in Kosher delicatessens in America. Taco de lengua (lengua being Spanish for tongue) is a taco filled with beef tongue, and is especially popular in Mexican cuisine. As part of Colombian gastronomy, Tongue in Sauce (Lengua en Salsa), is a dish prepared by frying the tongue, adding tomato sauce, onions and salt. Tongue can also be prepared as birria. Pig and beef tongue are consumed in Chinese cuisine. Duck tongues are sometimes employed in Szechuan dishes, while lamb's tongue is occasionally employed in Continental and contemporary American cooking. Fried cod "tongue" is a relatively common part of fish meals in Norway and Newfoundland. In Argentina and Uruguay cow tongue is cooked and served in vinegar (lengua a la vinagreta). In the Czech Republic and Poland, a pork tongue is considered a delicacy,and there are many ways of preparing it. In Eastern Slavic countries, pork and beef tongues are commonly consumed, boiled and garnished with horseradish or jelled; beef tongues fetch a significantly higher price and are considered more of a delicacy. In Alaska, cow tongues are among the more common.

Tongues of seals and whales have been eaten, sometimes in large quantities, by sealers and whalers, and in various times and places have been sold for food on shore.

Cultural aspects

Sticking one's tongue out at someone is considered a childish gesture of rudeness and/or defiance in many countries; the act may also have sexual connotations, depending on the way in which it is done. However, in Tibet it is considered a greeting. In 2009, a farmer from Fabriano, Italy was convicted and fined by the country's highest court for sticking his tongue out at a neighbor with whom he had been arguing. Proof of the affront had been captured with a cell phone camera. Blowing a raspberry can also be meant as a gesture of derision.

Body art

Being a cultural custom for long time, tongue piercing and splitting has become quite common in western countries in recent decades, with up to one-fifth of young adults having at least one piece of body art in the tongue.

Additional Images

• 

  Human pharynx. Posterior view.

• 

  Deep dissection of larynx, pharynx and tongue seen from behind

See also

• Electronic tongue
• Language
• Licking
• List of Mendelian traits in humans           
• Oral cancer
• Taste buds on the tongue
• "Tip-of-the-tongue" phenomenon

• Tongue splitting
• Tongue cleaner
• Tongue disease
• Tongue piercing
• Tongue rolling
• Tongue-twister
• Vocal tract

References

Notes

External links

• University of Manitoba, Anatomy of the Vocal Tract