Tongue

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Tongue
A 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[1]
MeSH	Tongue
Dorlands/Elsevier	Tongue

This article about a trait that is shared between many species might have an extensive bias or disproportional coverage towards one species. Please improve this article or discuss the issue on the talk page.

The tongue is a muscle on the floor of the mouth that manipulates food for chewing and swallowing (deglutition). It is the primary organ of taste, as much of the upper surface of the tongue is covered in papillae and taste buds. A secondary function of the tongue is speech. It is sensitive and kept moist by saliva, and is richly supplied with nerves and blood vessels to help it move. ^[2]

Description

Structure

Drawing of an anterior view of the tongue and oral cavity, with cheeks removed for clarity.

Lateral view of the tongue, with extrinsic muscles highlighted.

The tongue is made mainly of skeletal muscle. The tongue extends much further than is commonly perceived, past the posterior border of the mouth and into the oropharynx.

The dorsum (upper surface) of the tongue can be divided into two parts:

• an oral part (anterior two-thirds of the tongue) that lies mostly in the mouth
• a pharyngeal part (posterior third of the tongue), which faces backward to the oropharynx

The two parts are separated by a V-shaped groove, which marks the terminal sulcus

Other divisions of the tongue are based on the area of the tongue:

wings in the upper flap

Muscles

3/4 view of a 6.5 cm human tongue.

The intrinsic muscles lie entirely within the tongue, while the extrinsic muscles attach the tongue to other structures.

The extrinsic muscles reposition the tongue, while the intrinsic muscles alter the shape of the tongue for talking and swallowing.

Papillae and taste buds

The oral part of the tongue is covered with small bumpy projections called papillae. There are four types of papillae:

• filiform (thread-shape)
• fungiform (mushroom-shape)
• circumvallate (ringed-circle)
• foliate (leaf-shape)

All papillae except the filiform have taste buds on their surface. The circumvallate are the largest of the papillae. There are 8 to 14 circumvallate papillae arranged in a V-shape in front of the sulcus terminalis, creating a border between the oral and pharyngeal parts of the tongue.

There are no lingual papillae on the underside of the tongue. It is covered with a smooth mucous membrane, with a fold (the lingual frenulum) in the center. If the lingual frenulum is too taut or too far forward, it can impede motion of the tongue, a condition called ankyloglossia.

The upper side of the posterior tongue (pharyngeal part) has no visible taste buds, but it is bumpy because of the lymphatic nodules lying underneath. These follicles are known as the lingual tonsil.

The human tongue can detect five basic taste components: sweet, sour, salty, bitter and umami. The sense of taste is referred to as a gustatory sense. Contrary to the popular myth and generations of schoolbooks, there are no distinct regions for tasting different tastes. This myth arose because Edwin G. Boring replotted data from one of Wundt's students (Hanig) without labeling the axes, leading some to misinterpret the graph as all or nothing response.^[3] The common conception of taste has a significant contribution from olfaction.

Innervation

Motor innervation of the tongue is complex and involves several cranial nerves. All the muscles of the tongue are innervated by the hypoglossal nerve (cranial nerve XII) with one exception: the palatoglossal muscle is innervated by the X cranial nerve, the Vagus nerve via the pharyngeal plexus.

Sensory innervation of the tongue is different for taste sensation and general sensation.

• For the anterior two-thirds of the tongue, general sensations and taste sensations are carried via different nerves.
  • Somatic sensations travel from the tongue via the lingual nerve, a major branch of the mandibular nerve (itself a branch of the trigeminal nerve). This nerve also carries general sensation from areas of the oral mucosa and gingiva of the lower teeth.
  • Taste sensation is carried to the facial nerve via the chorda tympani. The chorda tympani also carries parasympathetic fibers from the facial nerve to the submandibular ganglion.
• The posterior one-third of the tongue has a simpler innervation, as both taste and general sensations are carried by the glossopharyngeal nerve.

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.^[4][5] In area is the lingual artery, a good place to stop uncontrolled bleeding in the tongue.

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

Length

The average length of the tongue from the oropharynx to the tip is 10 cm (4 in).^[6] Stephen Taylor holds the world record for the world's longest tongue. It measures 9.5 cm (3.7 in) from the tip to the center of his closed top lip. Annika Irmler holds the record for longest female tongue, at 7 cm (2.75 in).^[7]

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.^{[citation needed]}

Secondary uses

A woman licks a man's face.

In addition to eating and human vocalization, the human tongue has many secondary uses. These include certain forms of kissing known as "tongue kissing" or sometimes "french kissing" in which the tongue plays a primary role. Generally, use of the tongue (such as licking), or interaction between tongues, appears to be a common gesture of affection, not just in humans but throughout the animal kingdom, and particularly in mammals.

Because of its use in both the phenomenon of human sexual interactions, the tongue sometimes is associated with a sensual or erotic connotation. In art the human tongue is often depicted as a seductive instrument, similar to the status of the lips.

A tongue piercing

The tongue is also one of the more common parts of the human anatomy to be subject to piercing and body modification, a phenomenon that is sometimes associated with certain subcultures or demographics. Tongue piercing has appeared historically in many ancient cultures, and is an increasingly popular trend in the West today, particularly in youth culture.

Showing tongue (tongue out) is an international emotional gesture used primarily by children, or by adults behaving (deliberately or not) in a childish manner.

The human tongue also plays a valuable role in other acts, such as for blowing bubbles with bubble gum, whistling, cleaning, and moistening thread or envelope glue.

Non-human tongues

An okapi using its tongue to scratch an itch

Most multi-cellular animals, that is, members of the subkingdom Metazoa, have tongues or similar organs.

In animals such as dogs and cats, the tongue is often used to clean the fur and body. Rough textures of the tongues of these species helps them to use their tongues to remove oils and parasites by licking themselves and each other. Aside from daily uses for eating and drinking, a dog's tongue 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.^[8][9]

Some animals have prehensile tongues. For example, chameleons, frogs, anteaters, and some species of fish use their tongues to catch prey. Many insects have a type of tongue called a proboscis that is used for the same purpose or, in the case of butterflies, to drink nectar.^[10] The corresponding organ in ants is called the hypopharynx.^[11] Molluscs have a rough tongue called a radula,^[12] which they use to grind food.

Fish generally do not have a true tongue, although there are a few exceptions. The "tongue" of lampreys, for instance, is a rasping organ not homologous with the tongue of tetrapods such as humans.^[13]

Tongue rolling

Rolled Tongue

Cloverleaf Tongue

Tongue rolling is the act of rolling the tongue axially into a tube shape. The ability to roll the tongue has been generally believed to depend on genetic inheritance. Tongue rolling was believed to be a dominant trait with simple Mendelian inheritance, and is still commonly used as an example in high school and introductory biology courses. It provided a simple experiment to demonstrate inheritance.

There is little laboratory evidence, though, for the common belief that tongue rolling is inheritable and dominant. A 1975 twin study found that identical twins (who share all of their genes) were no more likely than fraternal twins (who share an average of half) to both have the same phenotype for tongue rolling.^[14][15]

Some people are able to generate a high pitched sound by blowing air through their rolled tongue.^{[citation needed]}

Cloverleaf tongue is the ability to fold the tongue in a particular configuration with multiple bends. To the extent to which it is genetic, it is probably a dominant trait distinct from tongue rolling.^[15]

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.^[16] 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".^[16] 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^[17] 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 humour. "Tongue twisted" is a term used to described being unable to pronounce a word or phrase correctly. A tongue twister is a phrase made specifically to be very difficult to pronounce. "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.

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

University of Manitoba, Anatomy of the Vocal Tract

Wikimedia Commons has media related to: tongue

Look up tongue in Wiktionary, the free dictionary.

v • d • e Taste Basic tastes Sweetness · Bitterness · Sourness · Saltiness · Umami Disorders Ageusia · Dysgeusia Other Aftertaste · Acquired taste · Epiglottis · Pharynx · Piquance · Scoville scale · Soft palate · Supertaster · Tongue See also: Sight · Hearing · Smell · Touch