Tongue and its development


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Tongue and its development

  1. 1. TONGUE AND ITS DEVELOPMENT INTRODUCTION: The tongue is a mobile muscular organ of deglutition; taste and speech which bulges upward from the floor of the mouth; and its posterior part forms the anterior wall of the oral part of the pharynx. It consists of 2 parts, namely the oral part and the pharyngeal part. The attachments of the tongue are as follows: Hyoid bone Mandible Styloid processes Soft palate Pharyngeal wall The tongue has 4 parts:- - Root - Dorsum - Apex - Inferior surface The Dorsum part of the tongue is convex in shape It is divided into - Sulcus terminalis - Anterior oral or pre sulcal - Posterior pharyngeal or post The oral and pharyngeal part differ 1
  2. 2. The oral part of the tongue is located in floor Pharyngeal forms the base of the tongue The Apex points towards the incisors * Posterior * Margin * Mucosa reflected laterally * Superiorly * Devoid of papillae The Root of the tongue is attached to the hyoid bone and mandible and its inferior relations are geniohyoid and mylohyoid. CLASSIFICATION: The tongue can be divided into 3 classes:- Class I: The tongue lies in the floor of the mouth with the tip forward and slightly below the incisal edges of the mandibular anterior teeth. Class II: The tongue is flattened and broadened but the tip is in its normal position. Class III: The tongue is retracted and depressed into the floor of the mouth with the tip facing upward, downward or assimilated into the body of the tongue. A Normal Tongue:- Is one where the tip of the tongue rests forward in a position just lingual to the mandibular anterior teeth. This is present in 65% subjects. A Retracted Tongue:- Causes the tissues of the sublingual gland to move posterior and inferior to break the seal between the mucous membrane overlying the sublingual gland. 35% subjects. Development of the tongue: Development of the tongue starts in the 4th month of intrauterine life. The tongue develops in relation to the pharyngeal arches in the floor of the developing mouth. Each pharyngeal arch arises as a mesodermal thickening in the lateral wall of the foregut and that it grows ventrally to become continuous with the corresponding arch of opposite side. The lingual swellings are partially separated from each other by another swelling that appears in the midline. This median swelling is called the tuberculum _____. Immediately behind the tubercular _____, the epithelium proliferates to form a down growth (thynoglossal duct) from which the thyroid gland develops. The site of this down-growth is subsequently marked by a depression called the foramen caecum. Another midline swelling is seen in relation to the medial ends of the second, third and fourth arches. This selling is called hypobranchial eminence which soon shows a subdivision into a cranial part related to the second and third arches (called the copula) and a candal part related to the 4th arch. The candal part forms the epiglottis. The anterior two third of the tongue is formed by fusion of the tuberculum impar, the two lingual swellings. The anterior 2/3rd of the tongue is thus derived from the mandibular arch. The posterior 1/3 of the tongue is formed from the cranial part of the hypobranchial eminence. The second arch mesoderm gets buried below the surface. The third arch mesoderm grows over it to fuse with the mesoderm of the first arch. The posterior one third of the tongue is thus from by third arch mesoderm. The posterior most of the tongue is derived from the fourth arch. 2
  3. 3. The anterior 2/3rd of the tongue is supplied by the lingual branch of mandibular nerve which is the posttraumatic nerve of the first arch and by the chorda tympani. The posterior 1/3 of the tongue is supplied by glossopharyngeal nerve which is the nerve of the third arch. The posterior most of the tongue is supplied by the superior laryngeal nerve which is the nerve of the fourth arch. The muscular of the tongue is derived from occipital myotomes. Developmental Disturbances of the Tongue: 1. Microglossia: Rare congenital anomaly; it refers to a Small or a rudimentary 2. The term Aglossia pertains to the absence of tongue 3. Macroglossia presents as a congenital and secondary anomaly. Its treatment is partial excision. 4. Ankyloglossia: Complete, partial. It is seen in tongue tied patients and those with speech difficulty 5. Cleft tongue can be either complete/ bifid Partial cleft is common It presents as a deep groove on dorsal surface of the tongue 6. Fissured tongue is another kind Malformation where small furrows or grooves are seen on the dorsal surface of the tongue. - Helparin and co-worker’s 1965 said increase with age and not a differential diagnosis - Extrinsic factor 7. Median rhomboid glossitis is a congenital anomaly ________ not retracted before fusion of lateral halves Etiology  ______ Ferman et al.  Diabeics Treatment not specific / antifungal 8. Benign migratory glossitis: Due to geographic condition wandering rash/ erythema migrans It is unknown in origin and is usually seen as desquamated area It first appears then regresses then reappears Ectopic geographic:- Lesions are seen in the buccal mucosa, gingiva, palate, lips, floor of the mouth. It was discovered by Bonazy and her associates 9. Hairy Tongue is an unusual condition - It is due to the hypertrophy of filliform papillae - Its Colour varies from yellowish white/ brown/ black depending on the foods consumed - Increased gagging reflex 10. Lingual varices: A dilated tortous vein:- subjected to increased hydrostatic pressure as it is poorly supported by surrounding tissue - Kleinman concluded that these represent aging - Prior 50yrs  premature 3
  4. 4. 11. Lingual thyroid nodule: A condition in which follicles of thyroid tissue are found in the substances of the tongue; possibly arising from the thyroid (anlage) that failed to migrate to its predestined position. May be manifested clinically as a nodular mass in or near the base of the tongue; in vicinity of foramen ceacum; but not necessarily in midline. Papillae: Refers to the projection of mucosa from the dorsum of the tongue. There are 4 types of papilla namely, Filliform: Fungiform:  is situated in the most presulcal area of the tongue  it is minute; conical; cylindrical in shape  Irregular cores of C.T., keratinized; whitish * Appear to increase the friction between the tongue and food; facilitating its movement  is Larger  More  vallate  Irregularly  dorsum  Deep red color  and usually bears one or more taste buds The Folate papillae: Vallate:  Lying bilaterally  forma a series of red; leaf like mucosal ridges by sides of the tongue -> sulcus terminalis.  it contains numerous taste buds.  Large cylindrical  8-12 in number; 1-2mm in size  its mucosa is narrower at base than apex  There are taste buds present Taste: “Mixture of several sensations”. Taste pores  Dorsal  Taste Primary:- Metallic ______: • More than 100 different taste; combination of primary studies show that the taste buds detects all types of tastes Other taste sensation:- Pain  Ginger Temperature  Flavor • Physiologist have deduced specific receptor for water Sweet : Organic substances; saccharides Salt : Chlorides of Na, K; NH4 Sour : H ion in acids an acidic salts Bitter: Organic compounds; alkaloids 4
  5. 5. TASTE BUDS: - Contain specialized receptors - They are barrel shaped cluster, 50-150 fusiform cells present; in oral cavity converging apically - It is 2 µm wide - 70 µm – 40 µm Mechanism: Substances in solution Attach to microreceptors Electrophysiologic changes Receptor’s stimulated (near fibers) Sends a message Brain Abnormalities of Taste Sensation: Aglusia: Refers to loss of taste sensation. Radiation of the oral cavity; causes destruction of the taste buds. Hypogeusia: Pertains to the decrease in taste sensation. Increase in threshold for different taste Taste not less completely Taste Blindness: Is rare genetic disorder The ability to recognize taste is lost Dysgeusia: Disturbance in taste sensation Biologic Consideration: 1. while sweet taste Provokes attraction Bitter taste provides rejection Herbivorous animals  bitter plants contain poisonous alkaloids 2. If there is specific need of a nutrient in body, animals often develop nack for it. e.g. Animals with Na deficiency enjoy drinking very salty solution, which normally they do not have the nack of MUSCLES OF TONGUE: Tongue is divided by a median fibrous septum; attached to the body of hyoid bone. It is divided into 2 namely, Intrinsic which is wholly within and Extrinsic  Extending outside Genioglossus is a fan shaped muscle: - Is triangular in sagital section 5
  6. 6. - Situated near and parallel to midline - Sup. Gen. tub behind mandibular symphysis - Upwards and backwards - Inferior fibres To upper anterior surface of hyoid bone - Muscles of opposite side - Posterior by lingual septum - Anterior variably blended Doran and Bagget (1972) considered no fibres reach the lingual apex in man or other mammals. Action: - Forward fraction of the muscle protrudes apex - Acting bilaterally, it depresses the central part of tongue making it concave from side to side - On the other hand acting unilaterally it diverges tongue to other side Hyoglossus: - It is thin quadrilateral muscle - It origins from the whole length of greater comu - And the front of the body of hyoid bone - Vertically up The fibres upwards and slightly forwards to be inserted between styloglossus and inferior long muscle - Fibres overlap Action: Depresses the tongue, making the dorsum convex and helps in retracting the protruded tongue. Chondroglossus: Part of hyoglossal - 2 cms long - Medial and base of lesser cornu adjoining part of hyoid bone Styloglossus: - Shortest and smallest muscle of tongue - It is inserted anterior lateral asp of styloid process - This muscle runs down and forwards - And it divides tongue longitudinally - And blends with inferior long muscle Action: Draws tongue up and backwards during swallowing Palatoglossus: - Small fasciculus muscle - This muscle is narrower at end than middle - It is inserted in the oral surface of palatine aponeurosis about ½ way along soft palate - Some fibres spread over the dorsum of tongue 6
  7. 7. Action: The palatoglossus elevates the root of tongue, approximates the palatoglossal arches and thus closes the oropharyngeal isthmus. INTRINSIC MUSCLES OF TONGUE: Consists of 2 muscles, namely the Sup. Long which forms a thin stratum on the dorsal lingual mucosa near median septum. It makes the dorsum concave. The second muscle is the inferior long which is a narrow band near inferior lingual surface between genio and hypoglossus. It extends from root to apex The transverse muscle passes laterally from the median fibrous septum to submucous fibrous tissue at lingual margin On the other hand the vertical muscle runs from dorsal to ventral aspect in the anterior part Action: Alter the shape by making the tongue broader. It also flattens the tongue. Superior/ inferior -> tend to shorten; The superior longitudinal muscle turns the apex and sides upwards to make dorsum concave whereas the inferior longitudinal muscle pulls the apex down  convex The transverse muscle makes the tongue narrow/ elongate and vertical muscle flattens/ widens the tongue. Nerve Supply: Muscles  Occipital somites Muscle membrane  Embryonic pharynx Venous Drainage: - Drain dorsum/ sides - Near the greater cornu of hyoid bone it joins the interior jugular - Begins at tip  runs back near the muscle membrane of tongue’s inferior surface - Near anterior border of hyoglossus  sublingual vein  ____jugular Applied Anatomy of the Tongue: 1. Injury to hypoglossal nerve produces paralysis of the muscles of the tongue on the side of the lesion. Supranuclear lesions of the hypoglossal nerve produces paralysis; like pseudobulbar palsy Tongue is small; stiff moves very sluggishly resulting in defective articulation. 2. In unconscious of  tongue falls back  obstructs airway 3. In epileptic patients – commonly bitten 4. CA of tongue  radiotherapy Enlarged Tongue are seen in cases of: - Down’s syndrome - Acromegaly - Strep. infection - Cancer of tongue 7
  8. 8. - Pellagra - Perncious anemia and - Hypothyroidism - Tongue may broaden in person with no teeth  denture Pain in Tongue are found in incidence where there is, - Glossitis - Geographic tongue - Post-menopausal women - Diabetic neuropathy  Tongue site for oral cancer, mouth ulcer, leukoplakia - Anemia - Cancer - Denture irritation - Ulcers - Referred pain - Heavy smoking - Minor infections - Injury - Allergic reaction to food - Antibiotic side effect The Causes of Tongue Tremor can be due to: - Neurological disorder - Overactive thyroid White Tongue can be seen where there is: - Local irritation as well as in case of those who are chronic smokers and those who consume alcohol. - Smoking and alcohol Smooth Tongue: Anemia and vitamin B12 deficiency are present in patients who comes with a complain of smooth tongue. Cases where the tongue shows a color Range from Pink  Magenta are as follows: - Folic acid and vitamin B-12 deficiency - Pellagra - Pernicious anemia - Plummer-Vinson syndrome - Sprue PROSTHODONTIC CONSIDERATION: 1. Speech Production: Tongue has a critical role and impact on speech production; and needs optimal mobility to lift; protrude; flatten form a groove and contact adjacent tissue freely. Tongue can be used for correct positioning of teeth. 2. Movements during border molding: 8
  9. 9. - Tongue distorts the lower denture easily - Border molding for lingual flange Anterior region Middle Posterior - Tongue to touch - Protrude - Protrude - Upper incisors - Sideways - Close and apply downward 3. Placement of teeth in dentures: Correct teeth positioning  Tongue biting avoided 4. Burning tongue is seen in: - Endocrine disturbance as well as - Residual monomer irritation 5. Sore tongue: - Causes initial discomfort - Tongue thrusting  denture Tongue has unfavorable movements Place the teeth in neutral zone area Displacement of mandibular denture bases by tongue movement during speech. Purpose: To evaluate denture displacement by denture base during speech. Conclusion: Tongue movements during speech induced only minimal displacement in dentures; additionally; tongue activity was found to be denture stabilizing rather than displacing in this study. Prosthetic Management of a total Glossectomy Defect in Edentulosu Patients: Total glossectomy with surgical reconstruction can result in significant alteration in the mandibular arch. In edentulous patient lingual vestibules along with mandibular alveolar ridge can be obliterated; with absence of lower anterior dentition; support of lower lip is lost and traction from surgical closure causes the lower lip to collapse in the oral cavity. Upper  Conventionally Cast poured lip and cheek Lower  Soft liner  Light body impression material Processed trial bases  J.R. recorded V.D.O. is reduced to minimize interferences  Speech  Swallowing Monoplane occlusal scheme Care to be taken to arrange mandibular teeth to give maxillary lip support. Try in is completed with patient approval and prosthesis is processed. Perception of roughness of restoration: Purpose – determine a threshold detection valve for surface roughness using tongue. Conclusion: Any surface which is more than 0.5 microns can be detected by the tongue. Unusual occurrence of tongue swelling after G.A. 9
  10. 10. Subjects denture can be used to separate the residual ridges during recovery period after G.A. This study concluded that before undergoing any procedure under G.A., edentulous patients should have a denture made. A patient who comes with a history of tongue Piercing : - Presents with Usual symptoms; pain, inflammation, difficulty in speaking and swallowing - This is considered unethetical for dentist - Use of lingual frenum in determining the original vertical position of mandibular anterior teeth Purpose:- To evaluate distance between anterior attachment of lingual frenum and incisal edges of mandibular teeth; as preextraction record. Concluded:- Distance 0.13mm; when frenum is recorded under function Tongue’s motor skills and masticatory performance in adult dentates; elderly dentates and complete denture wearers. Concluded that motor skills and masticatory performance decrease in relation to age. 10