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The tongue is the large bundle of muscles on the floor of the mouth that manipulates food for chewing and swallowing and is part of the digestive system. 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, and also plays a major role in sexuality, such as in the french kiss and oral sex.
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).
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 vallate (ringed-circle). All papillae except the filiform have taste buds on their surface. The vallate are the largest of the papillae. There are 8 to 14 vallate 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.
Items relating to the tongue are often called lingual, which comes from the Latin word, or glossal, which comes from the Greek word for tongue.
The tongue is the strongest muscle in the human body proportional to size.
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.
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 today, particularly in high schools and on campuses. Pop culture references to tongue piercings are common as well.
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 it's 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.
The act of tongue rolling describes one's ability to roll the tongue into a "hollow tube". The ability to roll the tongue is actually incumbent on genetic inheritance. Tongue rolling is thus a commonly explored experiment in highschool and introductory biology courses, as students examine it as a demonstrative concept for inheritance and in the initial understanding of genotypes and phenotypes.
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.
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