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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
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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.
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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
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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
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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
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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
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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
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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:
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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.
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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.
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