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ANATOMY AND PHYSIOLOGY OF TONGUE

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Anatomy OfTongue4BRISSO ARACKAL

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CONTENTSIntroductionParts of TongueMuscles of tongueIntrinsic musclesExtrinsic musclesAttachmentBlood supplyNerve supplyLymphatic drainage

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IntroductionVoluntary muscular structureOccupies floor of mouth3 inch long.Superior surface consist of stratified squamous epithelium with numerous papillae contains sensory receptors for the sense of taste in taste bud.

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Parts of the TongueRootLocated between the hyoid bone and mandible.Dorsal portion sits in the oropharynx.Attaches the tongue to roof of the mouth.BodyMakes up the anterior two-thirds of the tongue.Rough surface due to the lingual papillae.Surrounded by anterior and lateral teeth.Mobile portion of the tongue.ApexAlso known as the tip, is the anterior one-third of the anterior tongue surface.Rests against the incisor teeth.Highly mobile.

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Surface of the TongueThe top of the tongue (superior surface) has a V-shaped line known as the terminal sulcus that divides the tongue into the anterior and posterior surfaces.Theanteriorsurface is made up of the apex at the tip and body.Theposteriorsurface is made up entirely of the root.The inferior surface of the tongue (underside) is also made up of the body and apex.

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MUSCLES OF TONGUEA median fibrous septum divides the tongue into Rt. & Lt. halves. Each half contains 4 intrinsic & extrinsic muscles.Intrinsic musclesExtrinsic musclesSuperior longitudinalInferior longitudinalTransverse Vertical GenioglossusHypoglossus Styoglossus Palatoglossus 13BRISSO ARACKAL

Thelingual septumconsists of a vertical layer of fibrous tissue, extending throughout the entire length of themedian planeof thetongue, though not quite reaching thedorsum.It is thicker behind than in front, and occasionally contains a smallfibrocartilage, about 6mm. in length.It is well displayed by making a vertical section across the organ.

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INTRINSIC MUSCLESOccupy the upper part of tongue and attached to the submucous fibrous layer and to median fibrous septum.Alter the shape of tongue.4 in no. they are1. Superior longitudinal2. Inferior longitudinal3. Transverse4. Vertical15BRISSO ARACKAL

Superior longitudinal- beneath the mucous membrane.Shortens the tongue.Make dorsum concave.Inferior longitudinal-Lying close to inferior surface of tongue between genioglossus and hypoglossus.Shortens the tongue.Makes its dorsum convex.Transverse-Extend from median septum to the margins.Makes the tongue narrow and elongated.Vertical-Found at the borders of anterior part of tongue it make tongue broad & flattened.

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Superior longitudinal- fibrous tissue near epiglottis, hyoid and median fibrous septum to lateral margins of tongue and region of apex.Inferior longitudinal-root of tongue and corpus hyoid to tip below verticalis and transversus (apex of tongue)16

EXTRINSIC MUSCLES4 in no. they are1. Genioglossus2.Hyoglossus3. Palatoglossus4. Styoglossus

Connect to the tongue to mandible by Genioglossus, hyoid bone via Hyoglossus, Styloid process viz. Styloglossus and palate via Palatoglossus.

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Genioglossus-Fan shaped, form main bulk of tongue.Origin-Upper genial tubercle of mandible which run backward.Inserted-Upper fiber--tip-retracted the tip of tongueMiddle fiber-dorsum-depress tongueLower fiber- hyoid bone- pull posterior part of tongue forward and protrude out.

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inner surface of mandible at symphysis (at mental spine) to tip (but not extreme tip) and dorsum of tongue, along with hyoid body19

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Hyoglossus- Origin-Whole length of greater cornua and lateral part of body of hyoid bone.Fibers run upward and forwards.Insertion- Side of tongue between Styloglossus and inferior longitudinal muscle of tongue.Action- depresses tongue makes dorsum convex retracts and protruded tongue.

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length of the greater cornu and lateral body of hyoid to tissue on side of tongue (between styloglossus and inferior)21

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Palatoglossus-Origin-Oral surface of palatine aponeurosis.Insertion-Descends in the Palatoglossus arch to the side of tongue at junction of its oral and pharyngeal parts.Action-Pulls up the root of tongue, approximates the Palatoglossus arches and thus closes the oropharyngeal isthmus.

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anterior surface of soft palate through faucial pillar (anterolateral palatal aponeurosis) to posterolateral tongue body (sides of posterior tongue23

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Styoglossus-Shortest and smallestOrigin-Styloid process of temporal boneInsertion-Tip and sides of tongueAction-Retraction and elevation of tongue

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inferior sides of tongue to (elevates posterior tongue/retracts tongue)25

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Blood supplyExternal carotid artery- lingual branchLingual vein- joins to internal jugular veinRoot of tongue- tonsillar and ascending pharyngeal arteries. 27BRISSO ARACKAL

Nerve supply of muscles-Four extrinsic and 3 intrinsic muscles of tongue are supplied by IX C.N.Only palatoglossus supplied by vago-accessory complex.

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Lymphatic drainage-Tip of tongue-Drains bilaterally to the sub mental nodes.Remaining part-Ant. Rt. & lt. 2/3 drains unilaterally to the submandibular nodes.Few central lymphatics drains bilaterally to same nodesPost. 1/3 drains bilaterally to the jugulo-omohyoid nodes.

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PHYSIOLOGY OF TONGUE30BRISSO ARACKAL

CONTENTSTaste budsLocationStructure PapillaeTypes of papillaePhysiology of tasteNeural pathways for taste Function of tongue

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Taste BudTaste buds are sensory organs that are found on yourtongue and allow you to experience tastes that are sweet, salty, sour, and bitterThe sense of taste called gustation.10,000 taste buds are present in its papilla.A papilla contains few to 100 taste buds.

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Location of Taste BudsTaste buds contains sensory receptors found in the papillae of tongue and widely distributed in the epithelium of tongue, soft palate, pharynx and epiglottis.34BRISSO ARACKAL

Structure of Taste BudsOval barrel shape 70um*50um.Life span- 10 daysHaving opening called taste poresComposed of 5-15 gustatory receptors cell, 40 supporting cells or subtentacular cell and 15-20 transitional cells.

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Electron microscopic structure of taste buds

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Papillae The majority of taste buds on the tongue sit on raised protrusions of the tongue surface called papillae.37BRISSO ARACKAL

Types of papillae

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Fungiform papillaeAs the name suggests, these are slightly mushroom-shaped if looked at in longitudinal section. These are present mostly at the apex (tip) of the tongue, as well as at the sides. Innervated by facial nerve.

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Filiform papillaeThese are thin, long papillae. "V"-shaped cones That don't contain taste buds but are the most numerous. These papillae are mechanical and not involved in gustation. They are characterized by increased keratinization.

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Foliate papillaeFoliate papillae are short vertical folds found on the lateral margins of thetongue.They are occasionally Misdiagnosed as tumors or inflammatory disease. They are usually bilaterally symmetrical. Sometimes they appear small and inconspicuous, whereas they may be prominent. Lingual tonsils are found immediately beneath the foliate papillae and, when hyperplastic, cause a prominence of the papillae.

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these are ridges and grooves towards the posterior part of the tongue found at the lateral borders. Innervated by facial nerve (anterior papillae) and glossopharyngeal nerve (posterior papillae).

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Circumvallate papillae or vallate p.10 to 14 in no.Present at the back of the oral part of the tongue. They are arranged in a circular-shaped row just in front of the sulcus terminalis of the tongue. They are associated with ducts of Von Ebner's glands.innervated by the glossopharyngeal nerve.

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Ebner's glands, alsoVon Ebner's glandsareexocrine glandsfound in the mouth. More specifically, they areseroussalivary glandswhich reside within the moats surrounding thecircumvallate papillaein the posterior one-third of the tongue, anterior to theterminal sulcus.The Von Ebner glands are innervated by Cranial Nerve IX, theglossopharyngealnerve.It secreteslingual lipase.

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Cont It is generally accepted that there are four taste sensations, recently a fifth basic taste has been added: Sweet, sour, salty, bitter and the recently added umami (used in Asian kitchens produced by monosodium glutamate).

Salts, sweet, sour and umami tastes causes depolarization of the taste cells. Although different mechanisms are applied.

Bitter causes an internal release of Ca2+, no external Ca2+ is required.

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Physiology of TasteThe gustation involves stimulation of chemoreceptors by dissolved chemicals.The sensory receptors are stimulated by chemicals that enter the pores dissolved in saliva.Nerve impulses are generated and conducted along the glossopharyngeal from post.1/3rd, facial from ant. 2/3 tongue and vagus nerves from pharyngeal wall before synapsing in medulla and thalamus.Their final destination is the taste area in the parietal lobe of the cerebral cortex where taste is perceived.45BRISSO ARACKAL

MovementsProtrusion: Genioglossus on both sides acting togetherRetraction:Styloglossus and hyoglossus on both sides acting togetherDepression:Hyoglossus and genioglossus on both sides acting togetherElevation:Styloglossus and palatoglossus on both sides acting together

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Neural pathways for taste-The primary sensory neurons carrying taste sensation from taste buds are located in geniculate ganglion , superior petrosal ganglion and inferior ganglion ( ganglion nodosum) of facial glossopharyngeal and vagus nerves respectively.The peripheral processes of these cells connect with the taste buds, while central processes end in nucleus tractus solitarius (NTS).

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Conti..The secondary order sensory neurons arise from nucleus tractus solitarius, cross the midline, turn upwards to join the medial lemniscus and terminate in the posteroventral nucleus of thalamus.The third order sensory neurons arise from posteroventral nucleus of thalamus and project in the inferior part of the post central gyrus of the parietal lobe of the brain, the taste area of the cerebral cortex. 49BRISSO ARACKAL

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Function of TongueMastication Deglutition Speech Taste51BRISSO ARACKAL

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