EtymologyThe word tongue derives from the ''tunge'', which comes from *''tungōn''. It has in other —for example ''tonge'' in , ''tong'' in and , ''Zunge'' in , ''tunge'' in and , and ''tunga'' in , and . 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.
StructureThe tongue is a that forms part of the floor of the . The left and right sides of the tongue are separated by a vertical section of fibrous tissue known as the . This division is along the length of the tongue save for the very back of the pharyngeal part and is visible as a groove called the median sulcus. The human tongue is divided into parts by the terminal sulcus which is a V-shaped groove. The apex of the terminal sulcus is marked by a blind foramen, the foramen cecum, which is a remnant of the median in early . The anterior ''oral'' part is the visible part situated at the front and makes up roughly two-thirds the length of the tongue. The posterior ''pharyngeal'' part is the part closest to the , roughly one-third of its length. These parts differ in terms of their and . The anterior tongue is, at its apex, thin and narrow. It is directed forward against the lingual surfaces of the lower teeth. The posterior part is, at its root, directed backward, and connected with the by the and muscles and the , with the by three of mucous membrane, with the by the , and with the by the and the . It also forms the anterior wall of the . The average length of the human tongue from the to the tip is 10 cm. The average weight of the human tongue from adult males is 70g and for adult females 60g. In and , a distinction is made between the tip of the tongue and the blade (the portion just behind the tip). Sounds made with the tongue tip are said to be , while those made with the tongue blade are said to be .
Upper surface of the tongueThe upper surface of the tongue is called the dorsum, and is divided by a groove into symmetrical halves by the median sulcus. The foramen cecum marks the end of this division (at about 2.5 cm from the root of the tongue) and the beginning of the terminal sulcus. The foramen cecum is also the point of attachment of the and is formed during the descent of the in . The terminal sulcus is a shallow groove that runs forward as a shallow groove in a ''V'' shape from the foramen cecum, forwards and outwards to the margins (borders) of the tongue. The terminal sulcus divides the tongue into a posterior part and an anterior part. The pharyngeal part is supplied by the and the oral part is supplied by the (a branch of the mandibular branch (V3) of the ) for somatosensory perception and by the (a branch of the ) for . Both parts of the tongue develop from different es.
Undersurface of the tongueOn the undersurface of the tongue is a fold of mucous membrane called the that tethers the tongue at the midline to the floor of the mouth. On either side of the frenulum are small prominences called s that the major salivary s drain into.
MusclesThe 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= The four extrinsic muscles originate from bone and extend to the tongue. They are the , the (often including the ) the , and the . Their main functions are altering the tongue's position allowing for protrusion, retraction, and side-to-side movement. The genioglossus arises from the and protrudes the tongue. It is also known as the tongue's "safety muscle" since it is the only muscle that propels the tongue forward. The hyoglossus, arises from the and retracts and depresses the tongue. The chondroglossus is often included with this muscle. The styloglossus arises from the of the and draws the sides of the tongue up to create a trough for swallowing. The palatoglossus arises from the , and depresses the , moves the ''palatoglossal fold'' towards the midline, and elevates the back of the tongue during swallowing.
=Intrinsic= Four paired intrinsic muscles of the tongue originate and insert within the tongue, running along its length. They are the , the , the , and the . These muscles alter the shape of the tongue by lengthening and shortening it, curling and uncurling its apex and edges as in , and flattening and rounding its surface. This provides shape and helps facilitate speech, swallowing, and eating. The superior longitudinal muscle runs along the upper 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 , at the , 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 s that run along the sides.
Blood supplyThe tongue receives its supply primarily from the , a branch of the . The drain into the . The floor of the mouth also receives its blood supply from the lingual artery. There is also a secondary blood supply to the root of tongue from the and the . An area in the neck sometimes called the is formed by the intermediate tendon of the , the posterior border of the , and the nerve. The lingual artery is a good place to stop severe from the tongue.
Nerve supplyInnervation of the tongue consists of motor fibers, fibers for taste, and fibers for sensation. * Motor supply for all intrinsic and extrinsic muscles of the tongue is supplied by from the (CN XII), with the exception of the , which is innervated by the (CN X). Innervation of taste and sensation is different for the anterior and posterior part of the tongue because they are derived from different embryological structures ( 1 and pharyngeal arches 3 and 4, respectively). * Anterior two-thirds of tongue (anterior to the ): ** Taste: chorda tympani branch of the (CN VII) via fibers ** Sensation: lingual branch of the mandibular (V3) division of the (CN V) via fibers * Posterior one third of tongue: ** Taste and sensation: (CN IX) via a mixture of special and general visceral afferent fibers * Base of tongue ** Taste and sensation: internal branch of the (itself a branch of the , CN X)
Lymphatic drainageThe tip of tongue drains to the submental nodes. The left and right halves of the anterior two-thirds of the tongue drains to , while the posterior one-third of the tongue drains to the jugulo-omohyoid nodes.
MicroanatomyThe upper surface of the tongue is covered in , a type of which is of . Embedded in this are numerous , some of which house the s and their s. The lingual papillae consist of , , and , and only the filiform papillae are not associated with any taste buds. The tongue can divide itself in dorsal and ventral surface. The dorsal surface is a stratified squamous keratinized epithelium which is characterized by numerous mucosal projections called papillae. The lingual papillae covers the dorsal side of the tongue towards the front of the terminal groove. The ventral surface is stratified squamous non-keratinized epithelium which is smooth.
DevelopmentThe tongue begins to develop in the fourth week of from a median swelling – the (tuberculum impar) of the . In the fifth week a pair of lateral lingual swellings, one on the right side and one on the left, form on the first pharyngeal arch. These lingual swellings quickly expand and cover the median tongue bud. They form the anterior part of the tongue that makes up two-thirds of the length of the tongue, and continue to develop through . The line of their fusion is marked by the . In the fourth week a swelling appears from the second , in the midline, called the . During the fifth and sixth weeks the copula is overgrown by a swelling from the third and fourth arches (mainly from the third arch) called the , and this develops into the posterior part of the tongue (the other third). The hypopharyngeal eminence develops mainly by the growth of from the third pharyngeal arch. The boundary between the two parts of the tongue, the anterior from the first arch and the posterior from the third arch is marked by the terminal sulcus. The terminal sulcus is shaped like a ''V'' with the tip of the V situated posteriorly. At the tip of the terminal sulcus is the , which is the point of attachment of the where the embryonic begins to descend.
TasteChemicals that stimulate cells are known as . Once a tastant is dissolved in , it can make contact with the of the gustatory hairs, which are the sites of taste . The tongue is equipped with many on its surface, and each taste bud is equipped with taste receptor cells that can sense particular classes of tastes. Distinct types of taste receptor cells respectively detect substances that are sweet, bitter, salty, sour, spicy, or taste of . Umami receptor cells are the least understood and accordingly are the type most intensively under research.
MasticationThe tongue is an important accessory organ in the digestive system. The tongue is used for crushing food against the hard palate, during mastication and manipulation of food for softening prior to swallowing. The on the tongue's upper, or dorsal surface is ised. Consequently, the tongue can grind against the hard palate without being itself damaged or irritated.
SpeechThe intrinsic muscles of the tongue enable the shaping of the tongue which facilitates .
IntimacyThe tongue plays a role in and . The tongue is part of the of the mouth and can be used in intimate contact, as in the and in . The tongue can be used for stimulating the and other areas of the vulva.
DiseaseA of the tongue is that of also known as ''tongue-tie''. The tongue is ''tied'' to the floor of the mouth by a very short and thickened and this affects speech, eating, and swallowing. The tongue is prone to several including and other s such as , and ; , , (thrush), and . There are several types of that mainly affect the tongue. Mostly these are s. Food debris, and often form a visible tongue coating. This coating has been identified as a major factor contributing to (halitosis), which can be managed by using a .
Medication deliveryThe region underneath the front of the tongue is an ideal location for the of certain medications into the body. The is very thin underneath the tongue, and is underlain by a plexus of veins. The sublingual route takes advantage of the highly 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 (apart from ) of to a patient suffering chest pain from .
Other animalsThe muscles of the tongue evolved in from s. Most amphibians show a proper tongue after their . As a consequence most animals—amphibians, reptiles, birds, and mammals—have tongues (the family of lack tongue). In mammals such as s and s, the tongue is often used to clean the fur and body by . The tongues of these species have a very rough texture which allows them to remove oils and parasites. Some dogs have a tendency to consistently lick a part of their foreleg which can result in a known as a . 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, s, s, s and s have tongues. Other animals may have organs that are to tongues, such as a 's or a on a , but these are not with the tongues found in vertebrates and often have little resemblance in function. For example, butterflies do not lick with their proboscides; they suck through them, and the proboscis is not a single organ, but two jaws held together to form a tube. 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 s.
Society and culture
Figures of speechThe tongue can be used as a for ''language''. For example, the of the Bible, in the Book of , ' disciples on the Day of received a type of : "there appeared unto them cloven tongues like as of fire, and it sat upon each of them. And they were all filled with the , and began to speak with other tongues ....", which amazed the crowd of ish people in , who were from various parts of the but could now understand what was being preached. The phrase ' is used as a child's first language. Many languages have the same word for "tongue" and "". A common temporary failure in word from is referred to as the ' . The expression ' refers to a statement that is not to be taken entirely seriously – something said or done with subtle ironic or sarcastic humour. A ' is a phrase made specifically to be very difficult to pronounce. Aside from being a , "tongue-tied" means being unable to say what you want 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 . The "gift of tongues" refers to when one is uncommonly gifted to be able to speak in a foreign language, often as a type of . 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 , and a smooth-talking person said to have a .
GesturesSticking one's tongue out at someone is considered a childish gesture of or defiance in many countries; the act may also have sexual connotations, depending on the way in which it is done. However, in it is considered a greeting. In 2009, a farmer from , Italy, was convicted and fined by 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.
Body artand have become more common in western countries in recent decades. In one study, one-fifth of young adults were found to have at least one type of oral piercing, most commonly the tongue.
As foodThe tongues of some animals are consumed and sometimes considered delicacies. Hot tongue sandwiches are frequently found on menus in s in America. (''lengua'' being Spanish for tongue) is a taco filled with , 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 . Pig and beef tongue are consumed in Chinese cuisine. tongues are sometimes employed in dishes, while 's tongue is occasionally employed in Continental and contemporary American cooking. Fried "tongue" is a relatively common part of fish meals in and . In and 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.
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