Editing Tongue (section)

===Structure===
[[File:Facies inferior linguae.JPG|right|thumb|175px|The underside of a human tongue, showing its rich blood supply.]]
The tongue is a [[muscular hydrostat]] that forms part of the floor of the [[Human mouth|oral cavity]]. The left and right sides of the tongue are separated by a vertical section of fibrous tissue known as the [[lingual septum]]. 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 [[Anatomical terms of location#Anterior and posterior|anterior and posterior]] 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 [[thyroid diverticulum]] in early [[embryogenesis|embryonic development]]. 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 [[throat]], roughly one-third of its length. These parts differ in terms of their [[embryogenesis|embryological development]] and [[innervation|nerve supply]].

The anterior tongue is, at its apex, thin and narrow. It is directed forward against the lingual surfaces of the lower [[incisor]] teeth. The posterior part is, at its root, directed backward, and connected with the [[hyoid bone]] by the [[hyoglossi]] and [[genioglossi]] muscles and the [[hyoglossal membrane]], with the [[epiglottis]] by three [[glossoepiglottic folds]] of mucous membrane, with the [[soft palate]] by the [[glossopalatine arches]], and with the [[pharynx]] by the [[superior pharyngeal constrictor muscle]] and the [[mucous membrane]]. It also forms the anterior wall of the [[oropharynx]].

The average length of the human tongue from the [[oropharynx]] to the tip is 10&nbsp;cm.<ref>{{cite book |year=1997 |last=Kerrod |first=Robin |title=MacMillan's Encyclopedia of Science |publisher=Macmillan Publishing Company, Inc. |volume=6 |isbn=0-02-864558-8}}</ref> The average weight of the human tongue from adult males is 99g and for adult females 79g.<ref>{{cite journal |last1=Nashi |first1=Nadia |title=Lingual fat at autopsy |journal=Laryngoscope |date=Aug 2007 |volume=117 |issue=8 |pages=1467–1473 |doi=10.1097/MLG.0b013e318068b566 |pmid=17592392 |url=https://pubmed.ncbi.nlm.nih.gov/17592392/ |access-date=30 August 2023}}</ref>

In [[phonetics]] and [[phonology]], 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 [[apical consonant|apical]], while those made with the tongue blade are said to be [[laminal consonant|laminal]].

====Upper surface====
[[File:Foramen caecum.png|thumb|right|200px|Foramen cecum and terminal sulcus labelled above]]
[[File:Tongue.svg|thumb|200px|Features of the tongue surface]]
The upper surface of the tongue, the dorsal surface, 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&nbsp;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 [[thyroglossal duct]] and is formed during the descent of the [[thyroid diverticulum]] in [[human embryogenesis|embryonic development]].

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 [[pharynx|pharyngeal]] part and an anterior [[Human mouth|oral]] part. The pharyngeal part is supplied by the [[glossopharyngeal nerve]] and the oral part is supplied by the [[lingual nerve]] (a branch of the mandibular branch (V3) of the [[trigeminal nerve]]) for somatosensory perception and by the [[chorda tympani]] (a branch of the [[facial nerve]]) for [[taste|taste perception]].

Both parts of the tongue develop from different [[pharyngeal arch]]es.

====Undersurface====
On the undersurface, the ventral surface, of the tongue is a fold of mucous membrane called the [[frenulum of tongue|frenulum]] that tethers the tongue at the midline to the floor of the mouth. On either side of the frenulum are small prominences called [[Submandibular gland#Structure|sublingual caruncle]]s that the major salivary [[submandibular gland]]s drain into.

====Muscles====
The 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=====
[[File:Hyoglossus.png|thumb|right|220px|Lateral view of the tongue, with extrinsic muscles highlighted]]
The four extrinsic muscles originate from bone and extend to the tongue. They are the [[genioglossus]], the [[hyoglossus]] (often including the [[chondroglossus]]) the [[styloglossus]], and the [[palatoglossus]]. Their main functions are altering the tongue's position allowing for protrusion, retraction, and side-to-side movement.<ref name="GRAYS2005">{{cite book|title=Gray's anatomy for students|date=2005|publisher=Elsevier|isbn=978-0-8089-2306-0|location=Philadelphia, Pennsylvania |pages=989–995|first1=Richard L. | last1 = Drake | first2 = Wayne | last2 = Vogl | first3 = Adam W. M. | last3 = Mitchell}}</ref>

The genioglossus arises from the [[mandible]] 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 [[hyoid bone]] and retracts and depresses the tongue. The chondroglossus is often included with this muscle.

The styloglossus arises from the [[Temporal styloid process|styloid process]] of the [[temporal bone]] and draws the sides of the tongue up to create a trough for swallowing.

The palatoglossus arises from the [[palatine aponeurosis]], and depresses the [[soft palate]], moves the ''palatoglossal fold'' towards the midline, and elevates the back of the tongue during swallowing.

=====Intrinsic=====
[[File:Gray1020.png|thumb|right|240px|Coronal section of tongue, showing intrinsic muscles]]
Four paired intrinsic muscles of the tongue originate and insert within the tongue, running along its length. They are the [[superior longitudinal muscle of tongue|superior longitudinal muscle]], the [[inferior longitudinal muscle]], the [[vertical muscle of tongue|vertical muscle]], and the [[transverse muscle of tongue|transverse muscle]]. These muscles alter the shape of the tongue by lengthening and shortening it, curling and uncurling its apex and edges as in [[tongue rolling]], and flattening and rounding its surface. This provides shape and helps facilitate speech, swallowing, and eating.<ref name=GRAYS2005 />

The superior longitudinal muscle runs along the upper surface of the tongue under the mucous membrane, and functions to shorten and curl the tongue upward. It originates near the [[epiglottis]], at 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. It functions to shorten and curl the tongue downward.

The vertical muscle is located in the middle of the tongue, and joins the superior and inferior longitudinal muscles. It functions to flatten the tongue.

The transverse muscle divides the tongue at the middle, and is attached to the [[mucous membrane]]s that run along the sides. It functions to lengthen and narrow the tongue.

====Blood supply====
[[File:Gray559.png|thumb|Blood supply of the tongue]]
The tongue receives its [[blood]] supply primarily from the [[lingual artery]], a branch of the [[external carotid artery]]. The [[lingual veins]] drain into the [[internal jugular vein]]. The floor of the mouth also receives its blood supply from the lingual artery.<ref name=GRAYS2005 /> There is also a secondary blood supply to the root of tongue from the [[tonsillar branch of the facial artery]] and the [[ascending pharyngeal artery]].

An area in the neck sometimes called the [[Pirogov triangle]] is formed by the intermediate tendon of the [[digastric muscle]], the posterior border of the [[mylohyoid muscle]], and the [[hypoglossal]] nerve.<ref>{{cite web | url = http://www.whonamedit.com/synd.cfm/3186.html | title = Pirogov's triangle | work =  Whonamedit? - A dictionary of medical eponyms | publisher = Ole Daniel Enersen }}</ref><ref>{{cite journal |title=Topographic anatomy of lingual arterial anastomoses; Pirogov-Belclard's triangle |last1=Jamrozik |first1=T. |last2=Wender |first2=W. |journal=Folia Morphologica |volume=3 |issue=1 |pages=51–62 |date=January 1952 |pmid=13010300}}</ref> The lingual artery is a good place to stop severe [[hemorrhage]] from the tongue.

====Nerve supply====
Innervation of the tongue consists of motor fibers, [[special visceral afferent|special sensory]] fibers for taste, and [[general visceral afferent|general sensory]] fibers for sensation.<ref name=GRAYS2005 />
* Motor supply for all intrinsic and extrinsic muscles of the tongue is supplied by [[efferent nerve fiber|efferent motor nerve fibers]] from the [[hypoglossal nerve]] (CN XII), with the exception of the [[palatoglossus]], which is innervated by the [[vagus nerve]] (CN X).<ref name=GRAYS2005 />

Innervation of taste and sensation is different for the anterior and posterior part of the tongue because they are derived from different embryological structures ([[pharyngeal arch]] 1 and pharyngeal arches 3 and 4, respectively).<ref>{{Cite book | edition = Sixth | publisher = LWW | isbn = 978-1451190380 | last = Dudek | first = Dr Ronald W. | title = Board Review Series: Embryology | date = 2014}}</ref>
* Anterior two-thirds of tongue (anterior to the [[Lingual papilla#Circumvallate papillae|vallate papillae]]):
** Taste: chorda tympani branch of the [[facial nerve]] (CN VII) via [[special visceral afferent]] fibers
** Sensation: lingual branch of the mandibular (V3) division of the [[trigeminal nerve]] (CN V) via [[general visceral afferent]] fibers
* Posterior one third of tongue:
** Taste and sensation: [[glossopharyngeal nerve]] (CN IX) via a mixture of special and general visceral afferent fibers
* Base of tongue
** Taste and sensation: internal branch of the [[superior laryngeal nerve]] (itself a branch of the [[vagus nerve]], CN X)

==== Lymphatic drainage ====
The tip of tongue drains to the submental nodes. The left and right halves of the anterior two-thirds of the tongue drains to [[submandibular lymph nodes]], while the posterior one-third of the tongue drains to the jugulo-omohyoid nodes.

====Microanatomy====
[[File:Human tongue (251 09) Section.jpg|thumb|right|Section through the human tongue; stained [[Hematoxylin and eosin stain|H&E]]]]
The upper surface of the tongue is covered in [[oral mucosa#Classification|masticatory mucosa]], a type of [[oral mucosa]], which is of [[oral mucosa#Types|keratinized stratified squamous epithelium]]. Embedded in this are numerous [[lingual papilla|papillae]], some of which house the [[taste bud]]s and their [[taste receptor]]s.<ref>{{cite web|title=taste bud anatomy|url=http://www.britannica.com/science/taste-bud|website=Encyclopædia Britannica | first1 = Elizabeth | last1 = Bernays | first2 = Reginald | last2 = Chapman }}</ref> The lingual papillae consist of [[filiform papillae|filiform]], [[fungiform papillae|fungiform]], [[vallate papillae|vallate]] and [[foliate papillae]],<ref name=GRAYS2005 /> 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.<ref>{{cite book|last1=Fiore|first1=Mariano|last2=Eroschenko|first2=Victor|title=Di Fiore's atlas of histology with functional correlations|date=2000|publisher=Lippincott Williams & Wilkins|pages=238|url=http://www.almustafauniversity.com/wp-content/uploads/2016/04/difiores-atlas-of-histology-with-functional-correlations-11th-ed.pdf |url-status=dead |archive-url=https://web.archive.org/web/20170621161523/http://www.almustafauniversity.com/wp-content/uploads/2016/04/difiores-atlas-of-histology-with-functional-correlations-11th-ed.pdf |archive-date=21 June 2017}}</ref> 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.<ref>{{cite book|last1=Hib|first1=José|title=Histología de Di Fiore: texto y atlas|url=https://archive.org/details/histologiadedifi00hibj|url-access=limited|date=2001|publisher=El Ateneo|location=Buenos Aires|isbn=950-02-0386-3|page=[https://archive.org/details/histologiadedifi00hibj/page/n196 189]}}</ref>