Tongue

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 one of the organs of taste. Much of the surface of the tongue is covered in taste buds. The tongue assists in forming the sounds of speech.

The word tongue can be used as a synonym for language, as in the phrase mother tongue. In fact, in the Portuguese, Russian, Persian, Greek, Spanish (lengua), Polish, Slovak, Czech, Armenian, Finnish, Irish, Latin 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, γλωσσα.

It is also examined and observed diagnostically in traditional Chinese medicine.

Structure

The tongue is made mainly of skeletal muscle and attached to the hyoid bone, mandible and the styloid processes of the temporal bone.

The muscles that attach the tongue are the extrinsic muscles of the tongue. Inside the tongue, there are four pairs of intrinsic muscles that can alter the shape of the tongue for talking and swallowing. Since it contains no supporting skeletal structures for the muscles, the tongue is an example of a muscular hydrostat, like an octopus arm.

The dorsum (top side) of the tongue can be divided into two parts, a pharyngeal part (posterior third of the tongue), which faces backward to the oropharynx, and an oral part (anterior two-thirds of the tongue) that lies mostly in the mouth. The two parts are separated by a V-shaped groove, which marks the sulcus terminalis (or terminal sulcus).

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), foliate (leaf-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.

Taste from the oral part (anterior two-thirds) of the tongue is provided by cranial nerve VII, the facial nerve via the chorda tympani. Taste and somatic sensation from the posterior third of the tongue is provided by cranial nerve IX, the glossopharyngeal nerve.

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.

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 toungue 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, there are no distinct regions for tasting different tastes.

Use of tongue in pharmacy

The underneath segment of the toungue, sublingual, dosage route is a vital method of 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 pectoralis, 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.

Intrinsic muscles of the tongue

Four pairs of muscles originate within the tongue, and run in parallel down its length.
*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; and is controlled by the XII hypoglossal nerve.
*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.

The tongue is the strongest muscle in the human body proportional to size.

White tongue

White spots and patches or coating of the tongue are a symptom of several medical conditions:
* Antibiotics side effect
* Candidiasis
* Debauch
* Dehydration
* Leukoplakia
* Keratosis pharyngis
* Jaundice - causes a yellow tongue
* "Lie Bumps" - small dots usually on tip of tongue

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.

Non-human tongues

An Okapi using its tongue to scratch an itch

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 fishes 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.

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]

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.

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.

Trivia

*Tung was also the original Webster spelling of tongue
*Stephen Taylor holds the world record for the world's longest tongue. It measures 9.4 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]

External link

*The definition of tongue from Stedman's Online Medical Dictionary, 27th Edition

Tongue: Encyclopedia BETA

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