Tongue

Tongue
Latin	lingua
Vein	lingual
Nerve	Anterior 2/3: lingual nerve & chorda tympani Posterior 1/3: Glossopharyngeal nerve (IX)
Precursor	pharyngeal arches, lateral lingual swelling, tuberculum impar[1]
MeSH	Tongue
Dorlands/Elsevier	Tongue

The tongue is a group of muscles on the floor of the mouth that manipulates food for mastication. It is the primary organ of taste, 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.^[2]

Description

Musculature

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 aren't attached to any bone. The four extrinsic muscles act to change the position the tongue, and are anchored to bone.

Intrinsic muscles

1. Superior longitudinal fibers: shorten the tongue.
2. Inferior longitudinal fibers: shorten the tongue.
3. Vertical fibers: flatten and widen the tongue
4. Transverse fibers: narrow and elongate the tongue.

Extrinsic muscles

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

Vasculature

The underside of a human tongue

The tongue receives its blood supply primarily from the lingual artery, a branch of the external carotid artery. 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.^[3][4] 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.

Nerve supply

Taste for the anterior 2/3 of the tongue is supplied by the Facial nerve(Chorda tympani, CN7). General sensation of the anterior 2/3 is supplied by the Lingual nerve which is a branch of V3 of the Trigeminal nerve CN V.

Taste as well as general sensation for the posterior 1/3 is supplied by the Glossopharyngeal nerve (CN 9).

All intrinsic and extrinsic muscles of the tongue is supplied by the Hypoglossal nerve (CN 12), except for one of the extinsic muscles, palatoglossus, which is inervated by CN10 of the pharyngeal plexus.

Length

The average length of the human tongue from the oropharynx to the tip is 10 cm (4 in).^[5]

Use in pharmacy

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 (apart from I.V. administration) convenient and efficacious route of administration of nitroglycerin to a patient suffering angina pectoris, chest pain. If the tablet is swallowed, the medication is completely neutralized by the detoxification process of the liver.

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.^[6][7]

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.^[8][9]

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 related to the tongues found in vertebrates.

As food

The tongues of some animals are consumed and sometimes considered delicacies. In Alaska and the United Kingdom, cow tongues are among the more common. Hot tongue sandwiches are frequently found on menus in Kosher delicatessens in America. In the United Kingdom tongue can often be found at the local grocer, where it is often sold in reformed slices of meat after being ground up and set in gelatine. Taco de lengua (lengua being Spanish for tongue) is a taco filled with beef tongue, and is especially popular in Mexican cuisine. 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 the Czech Republic & 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.

Etymology

The word tongue derives from the Old English tunge, which comes from Proto-Germanic *tungōn.^[10] 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".^[10] 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^[11] 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.

Cultural aspects

Sticking one's tongue out at someone is a considered a childish gesture of rudeness and/or defiance in many countries. The act may also have obscene sexual connotations, depending on the way in which it is done. 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.^[12]

Blowing a raspberry can also be meant as a gesture of derision.

See also

• Electronic tongue
• Language
• List of Mendelian traits in humans
• Taste buds on the tongue
• Tip-of-the-tongue phenomenon
• Tongue splitting
• Tongue cleaner
• Tongue piercing
• Tongue-twister
• Vocal tract
• Tongue disease
• Oral cancer

Notes

External links