2. Anatomy of the tongue and its applied aspects.pptx

Anatomy of tongue.

1. ANATOMY OF THE TONGUE AND ITS APPLIED ASPECTS Dr. Chandini Ravikumar 1st year PG

2. CONTENTS Introduction Development of the tongue Parts of the tongue Papillae of the tongue Muscles of the tongue Arterial supply Venous drainage Lymphatic drainage Nerve supply Histology Taste buds Taste pathway Applied aspects of the tongue

3. INTRODUCTION Taste Speech Chewing Deglutition Tongue is a mobile, muscular organ situated in the floor of the mouth . It is associated with the functions of :- Tongue is covered by stratified squamous epithelium and comprises mainly of skeletal muscle , interspersed with a little fat and numerous glands. Its posterior part forms the anterior wall of the oropharynx .

4. DEVELOPMENT OF TONGUE The tongue begins to develop at about 4 weeks of gestation . Pharyngeal arches meet in midline beneath the primitive mouth. Local proliferation of the mesenchyme gives rise to a number of swellings in the floor of the mouth.

5. A s welling ( tuberculum impar ) arises in the midline in the mandibular process and is flanked by two other bulges, the lingual swellings . These lateral lingual swellings quickly enlarge and merge with each other and the tuberculum impar to form a large mass, from which the mucous membrane of anterior two-thirds of the tongue is formed.

6. The root of the tongue arises from a large midline swelling developed from mesenchyme of second, third, and fourth arches. This swelling consists of a copula and a large hypobranchial eminence (associated with the third and fourth arches).

7. As the tongue develops, the hypobranchial eminence overgrows the copula, which disappears. Posterior part of 4th arch marks the development of epiglottis . The tongue separates from the floor of the mouth by a down-growth of ectoderm around its periphery, which subsequently degenerates to form the lingual sulcus and gives the tongue mobility.

8. DEVELOPMENT OF TONGUE cont’d Epithelium Anterior two-thirds From two lingual swellings, which arise from the first branchial arch . It is supplied by lingual nerve (post-trematic) of 1st arch and chorda tympani (pre-trematic) of 2nd arch

9. 2. Posterior one-third From cranial large part of hypobranchial eminence, i.e. from the third arch . It is supplied by the glossopharyngeal nerve . 3. Posterior most part Developed from the fourth arch . Supplied by the vagus nerve .

10. Muscles - develop from the occipital myotomes which are supplied by the hypoglossal nerve . Connective tissue - develops from the local mesenchyme .

11. PARTS OF THE TONGUE The dorsum is divided into oral and pharyngeal parts by a V-shaped sulcus terminalis . The inferior surface is confined to the oral part only . The root is attached to the styloid process and soft palate above , and to mandible and hyoid below . TONGUE ROOT TIP BODY CURVED UPPER SURFACE OR DORSUM INFERIOR SURFACE

12. The tip of the tongue forms the anterior free end which, at rest, lies behind the upper incisor teeth. The dorsum of the tongue is convex in all directions. It is divided into an oral part (anterior two-thirds), a pharyngeal part (posterior one-third), and a small posterior most part .

13. PARTS OF THE TONGUE cont’d The oral or papillary part of tongue is placed on the floor of the mouth. Its margins are free and in contact with the gums and teeth. The superior surface shows a median furrow and is covered with papillae which make it rough. Its oriented in horizontal plane .

14. PARTS OF THE TONGUE cont’d The inferior surface is covered with a smooth mucous membrane, which shows a median fold called the frenulum linguae . It is continuous with the mucosa covering the floor of the oral cavity. On either side of frenulum, there is a prominence produced by the deep lingual veins . More laterally there is a fold called the plica fimbriata that is directed forwards and medially towards the tip of the tongue.

15. The pharyngeal or lymphoid part of the tongue is separated by a faint V- shaped groove, the sulcus terminalis . Two limbs of the ‘V’ meet at a median pit, named the foramen caecum . They run laterally and forwards up to the palatoglossal arches . The foramen caecum repesents the site from which the thyroid diverticulum grows down in the embryo.

16. In some people a thyroglossal duct persists and connects the foramen caecum on the tongue with the thyroid gland in the neck. The posterior surface of the pharyngeal part, sometimes called the base of the tongue , forms the anterior wall of the oropharynx.

17. The posterior most part of the tongue is connected to the epiglottis by three-folds of mucous membrane. These are the median glossoepiglottic fold and the right and left lateral glossoepiglottic folds. On either side of the median fold, there is a depression called the vallecula . The lateral folds separate the vallecula from the piriform fossa .

18. The mucous membrane has no papillae . It is irregular in contour , and has many lymphoid follicles (small nodules of lymphoid tissue in the submucosa), that collectively constitute the lingual tonsil .

19. PAPILLAE OF THE TONGUE These are projections of mucous membrane or corium which give the anterior two-thirds of the tongue its characteristic roughness . Its types are:-

20. Circumvallate papillae They are large in size 1-2 mm in diameter and are 8-12 in number . They are situated immediately in front of the sulcus terminalis. The papillae are cylindrical projections surrounded by a circular sulcus. The walls of the papillae have taste buds .

21. 2. Fungiform papillae These are numerous near the tip and margins of the tongue, and some of them are also scattered over the dorsum. They are smaller than the vallate papillae but larger than the filiform papillae. Each papillae consists of a narrow pedicle and a large rounded head. They are distinguished by their bright red colour .

22. 3. Filiform papillae Small cone-shaped projections of the mucosa. It covers the presulcal area of the dorsum of the tongue, has a characteristic velvety appearance and covered with keratin. They are the most numerous of the lingual papillae. Each is pointed; apex is split into filamentous processes.

23. 4. Foliate papillae Linear folds of mucosa on the sides of the tongue near the terminal sulcus of tongue.

24. TASTE BUDS Taste buds are small, ovoid or barrel-shaped intraepithelial organs about 80 micrometer high and 40 micrometer thick . They extend from the basal lamina to the surface of the epithelium. Their outer surface is almost covered by a few flat epithelial cells, which surround a small opening, the taste pore .

25. The primary 4 taste sensations are sweet, salty, bitter and sour . They are perceived in different regions of the tongue and palate : Sweet at the tip of the tongue Salty at the lateral border of the tongue Bitter and sour on the palate and posterior part of the tongue

26. Bitter and sour taste sensations are mediated by the 9th nerve , and sweet and salty taste are mediated by the intermediofacial nerve by the chorda tympani .

27. TASTE PATHWAY The taste from anterior two-thirds of tongue except from vallate papillae is carried by chorda tympani branch of facial nerve till the geniculate ganglion . The central processes go to the tractus solitarius in the medulla. Taste from posterior one-third of tongue including the circumvallate papillae is carried by cranial nerve IX till the inferior ganglion . The central processes also reach the tractus solitarius.

28. TASTE PATHWAY cont’d Taste from posterior most part of tongue and epiglottis travels through Xth N till the inferior ganglion of vagus. These central processes also reach tractus solitarius. After a relay in tractus solitarius, the solitario-thalamic tract is formed which becomes a part of trigeminal lemniscus and reaches postero-venteromedial nucleus of thalamus of the opposite side. Another relay here takes them to lowest part of postcentral gyrus , which is the area for taste.

29. MUSCLES OF THE TONGUE The bulk of the tongue is composed of muscle. A middle fibrous septum divides the tongue into right and left halves. Each half contains four intrinsic and four extrinsic muscles. (All muscles of the tongue are paired .) Except for the palatoglossus , which is innervated by the vagus nerve , all muscles of the tongue are innervated by the hypoglossal nerve .

30. Intrinsic muscles Originates and inserts within the substance of the tongue. They occupy upper part of the tongue , and attached to the submucous fibrous layer and to median fibrous septum. They alter the shape of the tongue by: Lengthening and shortening it Curling and uncurling its apex and edges Flattening and rounding its surface.

31. The intrinsic muscles are divided into: The superior longitudinal muscle lies beneath the mucous membrane. The inferior longitudinal muscle is a narrow band lying close to the inferior surface of the tongue between the genioglossus and the hyoglossus. The transverse muscle extends from the median septum to the margins. The vertical muscle is found at the borders of the anterior part of the tongue .

32. Extrinsic muscles Originates from structures outside the tongue and insert into the tongue. These muscles protrude, retract, depress and elevate the tongue. The extrinsic muscles connect the tongue to the mandible via genioglossus ; to the hyoid bone via hyoglossus ; to the styloid process via styloglossus ; and palate via palatoglossus . The four extrinsic muscles are:- Genioglossus Hyoglossus Styloglossus Palatoglossus

33. MUSCLE ORIGIN INSERTION ACTIONS Palatoglossus Oral surface of palatine aponeurosis Descends in palatoglossal arch to the side of tongue at the junction of oral and pharyngeal parts Pulls up root of tongue , approximates palatoglossal arches and closes oropharyngeal isthmus .

34. MUSCLE ORIGIN INSERTION ACTIONS Hyoglossus Whole length of greater cornua and lateral part of hyoid bone Side of tongue between styloglossus and inferior longitudinal muscle of tongue Depresses tongue , makes dorsum convex, retracts the protruded tongue.

35. MUSCLE ORIGIN INSERTION ACTIONS Styloglossus Tip and part of anterior surface of styloid process Into the side of tongue Pulls tongue upwards and backwards, i.e. retracts the tongue .

36. MUSCLE ORIGIN INSERTION ACTIONS Genioglossus Upper genial tubercle of mandible Upper fibres into tip of the tongue. Middle fibres into dorsum. Lower fibres into hyoid bone. Retracts and depresses the tongue , pulls the posterior part of tongue forwards and protrudes tongue forwards.

37. ACTIONS OF MUSCLES INTRINSIC MUSCLES Superior longitudinal Shortens the tongue, makes it dorsum concave Inferior longitudinal Shortens the tongue, makes it dorsum convex Transverse Makes the tongue narrow and elongated Vertical Makes tongue broad and flattened EXTRINSIC MUSCLES Genioglossus Protrudes the tongue Hyoglossus Depresses the tongue Styloglossus Retracts the tongue Palatoglossus Elevates the tongue

38. ARTERIAL SUPPLY OF TONGUE The major artery of the tongue is the lingual artery, a branch of the external carotid artery (ECA). On each side , the lingual artery originates from the ECA in the neck adjacent to the tip of the greater horn of the hyoid. It forms an upward bend, then loops downward and forward to pass deep to the hyoglossus muscle , and accompanies the muscle through the aperture formed by the margins of the mylohyoid, superior constrictor, and middle constrictor muscles, and enters the floor of the oral cavity.

39. ARTERIAL SUPPLY OF TONGUE cont’d The lingual artery then travels forward in the plane between the hyoglossus and genioglossus muscles to the apex of the tongue. The root of the tongue is also supplied by the tonsillar artery a branch of facial artery, and ascending pharyngeal branch of external carotid.

40. VENOUS DRAINAGE OF TONGUE The arrangement of the veins of the tongue is variable. Two veins accompany the lingual artery , and one vein accompany the hypoglossal nerve . The tongue is drained by dorsal lingual and deep lingual veins. The deep lingual vein is the largest and principal vein of the tongue. It is visible on the inferior surface of the tongue .

41. VENOUS DRAINAGE OF TONGUE cont’d On each side, the deep lingual vein travels with the 12th nerve on the external surface of the hyoglossus muscle and passes out of the floor of the oral cavity through the aperture formed by the margins of the mylohyoid, superior and middle constrictor muscles. It joins the internal jugular vein (IJV) in the neck. The dorsal lingual vein follows the lingual artery between hyoglossus and genioglossus muscles, and drains into the IJV in the neck.

42. LYMPHATIC DRAINAGE The tip of the tongue drains bilaterally to the submental nodes . The right and left halves of the remaining part of the anterior two-thirds of the tongue drain unilaterally to the submandibular nodes . A few central lymphatics drain bilaterally to the deep cervical nodes. The posterior most part and posterior one third of the tongue drain bilaterally into the upper deep cervical lymph nodes including jugulodigastric nodes. The whole lymph finally drains to the jugulo-omohyoid nodes . These are known as the lymph nodes of the tongue .

43. Lymphatic plexus of tongue The plexus in the mucous membrane is continuous over the whole surface and also the intramuscular plexus. Behind the circumvallate papillae the plexus is coarse and the collecting vessels run towards the hyoid bone. A superficial and deep lymphatic network drains the oral tongue.

44. There are three main components of the deep lymphatic network for the oral tongue: anterior, lateral and central. The anterior (apical) pathway drains the tip of the tongue . Primarily it drains to level III or less likely level I. The lateral (marginal) group from the edge of the tongue drains the lateral one-third of the dorsum of the tongue (DOT) from TOT to the circumvallate papillae. These lymphatic channels drain to levels I, II or III . The central pathway descending in the middle line between the genioglossus muscle and in the muscular substance of the drains the central two-thirds of the tongue . The vessels drain to the group 1 nodes or course through a sublingual node, and terminate in group 3 nodes.

45. Principal sentinel lymph nodes Anterior part of the tongue Submental Submandibular Jugulo- omohyoid lymph nodes Lateral and middle part of the tongue Submandibular Jugulo-digastric Thyroid lymph nodes Root of the tongue Jugulo- digastric lymph nodes

46. NERVE SUPPLY Motor nerves All intrinsic and extrinsic muscles, except palatoglossus, are supplied by XII N. The palatoglossus is supplied by the pharyngeal branch of the vagus nerve . Seven out of eight muscles are supplied by hypoglossal nerve .

47. NERVE SUPPLY cont’d Sensory nerves Lingual nerve is the nerve of general sensation and the chorda tympani is the nerve of taste for the anterior two-thirds of the tongue except vallate papillae. The glossopharyngeal nerve is the nerve for both general sensation and taste for the posterior one-third of the tongue including the circumvallate papillae. The posterior most part of the tongue is supplied by vagus nerve through the internal laryngeal branch.

48. HISTOLOGY The bulk of the tongue is made up of striated muscles . The mucous membrane consists of a layer of connective tissue, lined by stratified squamous epithelium . On the oral part of the dorsum , it is thin, forms papillae, and is adherent to the muscles. On the pharyngeal part of the dorsum , it is very rich in lymphoid follicles. On the inferior surface , it is thin and smooth. Numerous glands, both mucous and serous lie deep to the mucous membrane.

49. APPLIED ASPECTS OF THE TONGUE Glossitis is usually a part of generalized ulceration of the mouth cavity or stomatitis. In certain anaemias , the tongue becomes smooth due to atrophy of the filiform papillae. The presence of a rich network of lymphatics and of loose areolar tissue in substance of the tongue is responsible for enormous swelling of tongue in acute glossitis . The tongue fills up the mouth cavity and protrudes out of it.

50. The undersurface of the tongue is a good site along with the bulbar conjunctiva for observation of jaundice . In unconscious patients , the tongue may fall back and obstruct the air passages. This can be prevented either by lying the patient on one side with head down (the ‘ tonsil position ’) or by keeping the tongue out mechanically.

51. Lingual tonsil in the posterior one-third of tongue forms part of Waldeyer’s ring . Carcinoma of the tongue is quite common. The affected side of the tongue is removed surgically. All the deep cervical lymph nodes are also removed, i.e. block dissection of neck because recurrence of malignant disease occurs in lymph nodes. Carcinoma of the posterior one-third of the tongue is more dangerous due to bilateral lymphatic spread .

52. Importance of lymphatics in cancer metastasis Cancer metastasis has two essential characteristics; an “ organ preference ” and a “ differential metastatic potential ”. Tumours grow locally in the tongue but invade and metastasize to cervical lymph nodes. The survival in tongue carcinoma is poor compared to other subsites in oral cavity. Predicting the lymphatic spread from cancer of the oral tongue can help in choosing the appropriate surgical procedure and in predicting the outcome .

53. Skip metastasis The literature suggests that the SCC of the oral tongue metastasize to clinically negative nodes in 20% to 30% of patients . But if the metastasis skips any regional lymph node and show dysplastic features into the peripheral lymph node, then it is known as ‘ skip metastasis ’ or ‘ nodal skip metastasis ’. Presence of skip metastasis upto level IV nodes makes extended supraomohyoid neck dissection a more plausible treatment of choice in surgical cases.

54. Genioglossus is called ‘ safety muscle of the tongue ’ because if paralysed , the tongue will fall back on oropharynx and block the air passage. During anaesthesia, tongue is pulled forwards to clear the air passage. Genioglossus is the only muscle of the tongue which protrudes it forwards. It is used for testing the integrity of hypoglossal nerve . If hypoglossal nerve of right side is paralysed, the tongue on protrusion will deviate to the right side. Normal left genioglossus will pull the base to left side and apex will get pushed to right side (apex and base lies at opposite ends).

55. Referred pain is felt in the ear in diseases of posterior part of the tongue, as 9th and 10th nerves are common supply to both the regions.

56. A thyroglossal cyst is a fibrous cyst that forms from a persistent thyroglossal duct. Thyroglossal cysts can be defined as an irregular neck mass or a lump which develops from cells and tissues left over after the formation of the thyroid gland during developmental stages.

57. Glossopharyngeal neuralgia is extreme pain in the back of the throat, tongue or ear. It is described to be intense, with electric shock-like pain , that can occur without warning or can be triggered by swallowing.

58. Developmental anomalies of the tongue AGLOSSIA MICROGLOSSIA MACROGLOSSIA ANKYLOGLOSSIA

59. FISSURED TONGUE MEDIAN RHOMBOID GLOSSITIS HAIRY TONGUE

60. LINGUAL THYROID NODULE CLEFT TONGUE LINGUAL VARICES

61. Benign lesions of the tongue LIPOMA FIBROMA NEUROFIBROMA RHABDOMYOMA LEIOMYOMA MUCOSAL NEUROMAS PAPILLOMA

62. CANDIDIASIS LEUKOPLAKIA APHTHOUS ULCER LICHEN PLANUS

63. General disorders with clinical signs on the tongue Bitten tongue Sports injuries Injuries from Grand Mal convulsions Fishbone and foreign bodies Crohn’s disease Ulcerative colitis Drug eruptions Sarcoid disease Cyanosis Diabetes Fungus infections Scurvy Leukemias and lymphomas Bleeding disorders Telangiectasia Disorders of blood and blood vessels 4. Involvement with gut disorders 2. Injuries 3. G eneral systemic disorders

64. Clinical applications Reconstruction following resection of oral structures Resurfacing of oral defects Fistula closure Hard and soft palate defects Alveolar clefts Tonsillar arch defect Tongue reconstruction Flap designs Anterior based flap Posterior based flap Lateral flap Median flap Ventral surface flap Central island flap Anterior based flap Posterior based flap Transverse dorsal flap Ventral surface flap

65. Transoral Robotic Surgery (TORS) procedure Suprahyoid pharyngotomy Transhyoid pharyngotomy Lip-split mandibulotomy Mandibular swing Pull-through procedures

66. REFERENCES B D Chaurasia’s Human Anatomy, 6th edition. Adam W.M.Mitchell , Gray’s anatomy for students, 2nd edition. Cunningham’s manual of practical anatomy, 16th edition. Tencate’s oral histology, 8th edition. Orban’s oral histology and embryology, 13th edition. Shafer’s textbook of Oral Pathology, 7th edition. D.W.Beaven , A colour atlas of the tongue in Clinical diagnosis.