From Encyclopedia Jr, free information reference for Kids
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For other uses, see Tongue (disambiguation).
The tongue is the large bundle of skeletal muscles on the floor of the mouth that manipulates food for chewing and swallowing, (deglutition). It is the primary organ of taste. Much of the surface of the tongue is covered in taste buds. The tongue with its wide variety of possible movements assists in forming the sounds of speech. It is sensitive and kept moist by saliva, richly supplied with nerves and blood vessels to help it be moved.
The word tongue can be used as a metonym for language, as in the phrase mother tongue. In fact, Portuguese, French (langue), Maltese (ilsien), Romanian, Russian, Persian, Greek, Spanish (lengua), Polish, Slovak, Czech, Armenian, Finnish, Irish, Italian, Latin, Urdu, Aramaic, and Turkic languages, have the same word for "tongue" and "language". A common temporary failure in word retrieval from memory is referred to as tip-of-the-tongue phenomenon.
Items relating to the tongue are often called lingual, which comes from the Latin word lingua, or glossal, which comes from the Greek word for tongue, γλώσσα.
It is also examined and observed diagnostically in traditional Chinese medicine.
The tongue is often cited as the "strongest muscle in the body," a claim that is disputed. See Also: Strongest human muscle
[edit] Structure
Drawing of an anterior view of the tongue and oral cavity, with cheeks removed for clarity.
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 and 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 sulcus terminalis (or terminal sulcus).
Since the tongue contains no bony supports for the muscles, the tongue is an example of a muscular hydrostat, similar in concept to an octopus arm. Instead of bony attachments, the extrinsic muscles of the tongue anchor the tongue firmly to surrounding bones and prevent the mythical possibility of 'swallowing' the tongue.
Other divisions of the tongue, are based on the area of the tongue:
| normal name |
fancy name |
adjective |
| tongue tip |
apex |
apical |
| tongue blade |
lamina |
laminal |
| tongue body |
dorsum (back) |
dorsal |
| tongue root |
|
radical |
[edit] Muscles of the tongue
Lateral view of the tongue, with extrinsic muscles highlighted.
The extrinsic muscles attach the tongue to the hyoid bone, mandible, soft palate, and the styloid processes of the temporal bone. These attaching extrinsic muscles are in contrast to the intrinsic muscles of the tongue which lie entirely within the tongue. The extrinsic muscles reposition the tongue, while the intrinsic muscles alter the shape of the tongue for talking and swallowing.
Extrinsic muscles of the tongue by definition originate from structures outside the tongue and insert into the tongue. The four paired extrinsic muscles protrude, retract, depress, and elevate the tongue:
- The Genioglossus muscle originates from the mandible; it protrudes the tongue as well as depressing its center.
- The Hyoglossus muscle originates from the hyoid bone; it depresses the tongue.
- The Styloglossus muscle originates from the styloid process; it elevates and retracts the tongue.
- The Palatoglossus muscle originates from the palatine aponeurosis; it depresses the soft palate, moves the palatoglossal fold towards the midline, and elevates the back of the tongue. The palatoglossus is the only muscle of the tongue not innervated by the hypoglossal nerve, instead it is innervated the pharyngeal branch of vagus nerve.
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. (Drake et al. 2005)
- 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 verticalis muscle is located in the middle of the tongue, and joins the superior and inferior longitudinal muscles.
- The transversus muscle divides the tongue at the middle, and is attached to the mucous membranes that run along the sides.
[edit] Papillae and taste buds
- See Also: Taste Bud
The oral part of the tongue is covered with small bumpy projections called papillae. There are three types of papillae: filiform (thread-shape), fungiform (mushroom-shape), and circumvallate (ringed-circle). 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 Tongue-tie (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 four basic taste components, sweet, sour, salty and bitter. 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. The common conception of taste has a significant contribution from olfaction.
[edit] Innervation of the Tongue
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 pharyngeal branch of vagus nerve (cranial nerve X).
Sensory innervation of the tongue is different for taste sensation and general sensation. In the pharyngeal part of the tongue (posterior third), taste and general sensations are carried by the glossopharyngeal nerve (cranial nerve IX).
All sensations from the oral part of the tongue (anterior two-thirds) (as well as areas of the oral mucosa and gingiva of the lower teeth) travel from the tongue via the lingual nerve, a major branch of the mandibular nerve (itself a branch of the trigeminal nerve, cranial nerve V). After leaving the oral cavity, some fibers branch from the lingual nerve to form the chorda tympani. The chorda tympani eventually joins the facial nerve (cranial nerve VII), and it carries parasmpathetic and taste fibers originating in the facial nerve to the oral part of the tongue.
[edit] Use of tongue in pharmacy
The sublingual region underneath the front of the tongue is a location where the oral mucosa is very thin, and underlied 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 effacatious route of administration of nitroglycerin capsules to a patient suffering angina pectoris, chest pain. If the caplet is swallowed, the medication is completely neutralized by the detoxification process of the liver. The impact of the liver on the nitroglycerine is called a one pass elimination process.
[edit] White tongue
White spots and patches or coating of the tongue are a symptom of several medical conditions:
- Antibiotics side effect
- Oral candidiasis
- Debauch
- Dehydration
- Leukoplakia
- Keratosis pharyngis
- Jaundice - causes a yellow tongue
- "Lie Bumps" - small dots usually on tip of tongue
[edit] Secondary uses
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.
The tongue also has a distinct use in both male and female forms of oral sex, and is typically used to a great extent in foreplay and traditional sexual intercourse as well. 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.
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. Pop culture references to tongue piercings are common as well.
The human tongue also plays a valuable role in other acts, such as for blowing bubbles with bubble gum, and whistling.
Injury to the tongue is often very painful. The muscle is vulnerable to various cancers.
[edit] Non-human tongues
Most animals, that is, members of the kingdom 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 cool down further cooling down the bloodflow.
Some animals have prehensile tongues. For example, chameleons, frogs, salamanders 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 [1]. The corresponding organ in ants is called the hypopharynx [2]. Molluscs have a rough tongue called a radula [3], which they use to grind food.
[edit] Tongue rolling
The act of tongue rolling describes one's ability to roll the tongue into a "hollow tube". 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 taught 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 heritable 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. [4] [5]
[edit] Food consumption
The tongues of some animals are consumed and sometimes even considered delicacies. In America and the United Kingdom, cow tongues are among the more common, and can often be found at the local grocer, where they are often sold in reformed slices of meat after being ground up and set in gelatine. Hot tongue sandwiches are frequently found on menus in Kosher delicatessens.
Tongues are also used in sausage making. Historically, buffalo tongue was once considered an especially exquisite dish, and is one of the reasons for the American Bison being hunted by humans to the point of near extinction.
[edit] Trivia
- Tung was also the original Webster spelling of tongue
- Stephen Taylor holds the world record for the world's longest tongue. It measures 9.5 centimeters from the tip to the center of his closed top lip. Annika Irmler holds the record for longest female tongue, at 7 centimeters.[6]
[edit] See also
- Human anatomy
- Saliva
- Taste buds on the tongue
- Tip-of-the-tongue phenomenon
- Tongue-twister
- Tongue piercing
- Tongue bifurcation
- Vocal tract
- Glossitis (tongue inflammation)
[edit] External links
[edit] References
| Sensory system - Gustatory system - |
| Tongue | Taste bud | Gustatory cortex | Basic tastes |
