Tongue is the most agile, adept and versatile appendage in the human body. It is essential for mastication, deglutition, taste and speech. Tongue has no internal bony skeletal base, it is a mass of muscle that must provide its own unique skeletal base. It is partly oral and partly pharyngeal in position. It is attached by its muscles to hyoid bone, mandible, styloid processes, soft palate and pharyngeal wall. It has a root, apex, a curved dorsum and an interior surface.
Development of Tongue
- At about 4th week of intrauterine life, a medium swelling called tuberculum impar appears in the endodermale ventral wall or floor of pharynx. A little later another swelling called lateral lingual swelling (from ant end of each first pharyngeal arch) appears an each side of tubercueum impar.
- Lateral swelling now enlarge, grow medially, fuse with each other and tuberculum impar. Lingual swelling thus form the ant 2/3rd or body of tongue. Since they are derived from 1st pharyngeal arches, thus innervated by lingual nerve (br of trigeminal N). Chorda tympanil (br of Facial N) also supplies the taste sensation.
- Meanwhile a second median swelling called copula, appears in the floor of pharynx behind the tuberculum impar. Copula extends forwards on each side of tuberculum impar and becomes V shaped. At this time, the ant ends of 2nd, 3rd, 4th pharyngeal arch enter this region. The ant ends of 3rd arch on each side over grow the other arches and extend into copula, fusing in midline.
Now the copula disappears. Thus the post 1/3 of the tongue is derived from 3rd pharyngeal arch thus innervated by glossopnaryngeal (both sensation & taste)
Ant 2/3 is separated from post 1/3 by a groove the sulcus terminalis , which represents the internal b/w lingual swellings of 1st pharyngeal arenas and ant ends of 3rd pharyngeal arches. Around the edge of ant 2/3 of tongue, endodearmal cells proliferate and grow inferiorly into underlying mesenchyme. Later these cells degenerate so that this part becomes free. Some cells remains of the endoderm in the midline to form the Lingual Frenium.
During development, the mucous membrane of post 1/3rd tongue becomes pulled anterior slightly, so that fibers of vagus N cross the sulcus terminalis to supply the taste buds (circumvallate papillae)
Muscles of tongue are derived from occipital myotomes, which at first are closely related to developing hind brain and later migrate inferiorly and interiorly around the pharynx and enter tongue. They carry along with them the fibers of hypoglossal Nerve
Parts of Tongue
Root Is attached to hyoid and mandible and b/w them is in contact inferiorly with geniohyoid and mylohyoid muscles.
Apex touches the incisor teeth.
Dorsum is generally convex at rest is divided into anterior and posterior parts by sulcus terminalis, whose limbs runs anterolaterally from a median foreman caecum to palato glossal arches.
Oral Part (pre suecal part) located in oral cavity and on its floor. Apex touches the incisor teeth. The margin is in contact with gums and teeth. Superior surface (dorsum) is related to hard and soft palates. One each side in front of palatoglossal arch are 4-5 vertical folds, the foliate papillae. Dorsal mucosa has a median sulcus is adherent to subjacent muscle of tongue and is papillated. Inferior muscosa is smooth, purplish and reflected on the oral floor and gums being connected to former by median frenulum. Deed lingual V is visible and lateral to vein is a fimbriata plica fori briata directed anteromedially towards lingual apex.
The pharyngeal (Post sulcual part) lies post to the palatoglossal arches and forms the ant wall of oropharynx. Its mucosa is reflected laterally on to the palatine tonsil and pharyngeal wall and posteriorly on to the epigeottic folds. It is devoid of papillal, has low elevations due to lymphoid nodules embedded in the submucosa, as lingual tonsil.
Lingual papillae:_ are projections of lamina propria which elevate the epithelium above the general level. They are numerous and limited to presulcus part of dorsum.
a) Vallate Papillae – are large, vary 8-12 in No. / they form a V shaped row immediately in front of sulcus terminalis. Each papilla is 1-2 mm in dia, encompassed by a circular depression of mucosa and surrounded by a wall (vallum). Papilla is truncated cone, attached at the smaller end, broad end is superficial and bearing secondary subepithelial papilla. Entire St is covered with stratified squamous epi. These are mushroom shaped, with largest mar the midline and decreasing in size laterally and anteriorly. Von Ebners (serous) glands empty into the trough and help to eliminate the soluble parts of food after they have acted on the taste buds.
b) Fungiform papillae – more numerous than vallate occur mainly on the lingual margins but also occur irregularly on the dorsum b/w filiform. Larger in size, round shaped and deep red in colour. Has secondary subepithelial papillal and bear numerous taste buds.
c) Fili form papillae – these cover most of the prisulcul dorsal area. These are minute, conical or cylindrical and arranged in rows parallel with vallate papillal except at lingual apex where they’re transverse. Also contain secondary subepethelial papellal, they are more pointed than the other two. Their epic may be split into fine processes, which are whitish, owing to thickened epi, its elongated celles being keratinized. These papillae don’t contain taste buds but increase the friction b/w tongue and food.
d) Foliate Papillae – Present on the post part of the lateral border of the tongue. These are sharp, low, parellal folds, but in man usually irregular and insignificant. Contain taste buds.
e) Papillae Simplices – cover the whole mucousmembrane of tongue, including the larger papillae.
Lingual Musculature Tongue is divided by a median fibrous septum, attached to the body of hyoid bone. In each half are both extrinsic and intrinisic muscles. Former extending outside the tongue. Latter wholly within it.
A) Genioglossus:- Is a strongest, triangular muscles lying near and parallel to the midline, arising from genial tubercle behind the mandibular symphysics above the origin of geniohyoid. From here it fans out backwards and upwards. The inferior fibers are attached by a thins aponeurosis to upper ant of hyoid bone near midline. Few fibers pass b/w hyoglossus and chandrogrossus to blend with pharyngeal middle constrictor. Intermediate fibers pass backwards. Superior fibers ascend towards to enter the whole length of the ventral surface of tongue from root to apex, intirmnging of opp sides are separated posteriorly by unequal septum, anteriory they are variably blended by decussation of fasciculi across the midline.
Action – It brings about forward traction of tongue to protrude its apex from month. Acting bilaterally they depress the central part of tongue, making it concave from side to side.
B) Hyoglossus is a thin, quadrilateral muscle, attached to whole length of the greater cornu and front of the body of the hyoid bone. It passes vertically up to enter the side of the tongue b/w styloglossus laterally and inferior longitundinal muscle medially. Fibers arising from hyoid body overlap those arising from greater corner. Bundles of hyoglossus that arise from lesser cornu are referred as chondroglossus. It is sometimes perforated by lingual A which runs forwards on outer surface before it plunges to inner surface. Mostly lingual A is situated entirely on inner surface.
Relations At superficial surface to diagastric tendon, stylohyoid, styloglossus, mylohyoid, lingual N, snbmandibular ganglion, sublingual gland, hyoglossal N, deep lingual V, deep part of submandibular gland and duct.
At Deep surface to stylohyoid ligament, genioglossus inferior longitudinal M, lingual A, glossopharyngeal N.
Post inferiorly is separated from middle constrictor by lingual A. Here it is in lateral pharyngeal wall below palatine tonsil.
Post border pass glossopharyngeal N, stylohyoid ligament and lingual A.
Action It depresses the tongue.
C) Styloglossus Arises from the anterior surface of the styloid process near its apex and styloid end of stylomandibular ligament. Passing down and forwards it divides at the side of tongue into a longitudinal part, which enters the tongue dorsolaterally to blend with inferior longitudinal muscle in front of hyoglossus, and an oblique part, overlapping the hyoglossus and decussating with it.
Action Draws the tongue up and backwards.
D) Palatoglossus Arises from lower surface of palatine aponeurosis. It runs downwards in curve of the palatoglossal arch to the tongue at its bend. Fibers continue transversely through the tongue, interlacing with transverse fibers to meet the muscle of opp side. Since fiber meet in midline of palatine aponeurosis and are continues within tongue, the muscle acts as a spincter separating oral and pharyngeal cavities in swallowing and speech.
Action Both sides muscles acting together bring the palatoglossal arches together thus shutting the oral cavity from the oropuarynx.
Chondroglossus Sometimes described as part of hyoglossus. Is separated from its fibers of the genoglossi which pass to the side of pharynx. It is 2cm long, arising from medial side and base of lesser cornu and adjoining part of hyoid bone and asecends to merge with intrinsic muscles b/w hyoglossus and genioglossus.
Action It aids hyoglossus in depressing the tongue.
Nerve Supply All the muscles of tongue are supplied by hypoglossal N except the palatoglossus which is supplied by cranial part of the accessory N.
A. Superior Longitudinal Muscle:- Is a thin stratum of oblique and longitudinal fibers lying beneath the dorsal lingual mucosa, extending towards from sub mucous fiberous tissue near epiglottis median lingual septum to lingual margins. Some fibers insert into mucous membrane.
B. Inferior Longitudinal Muscle is narrow band close to inferior lingual surface b/w genioglossus and hyoglossus. Extends from lingual root to apex. Some fibers being connected to body of hyoid bone. Anteriorly it blends with the styloglossus.
C. Transverse Muscle :- Passes laterally from median fibrous septum to subnucous fibrosis tissue at lingual margin, blending with palatopharyngeens.
D. Vertical Muscle:- Extends from dorsal to ventral aspects of tongue in its anterolateral region.
Action All intrinsic muscles alter the shape of tongue. Superior & inferior longitudinal tend to shorten it. Former turns apex and side upwards making tongue concave. Latter pulls apex down to make it convex. Transverse narrows and elongates the tongue. Vertical makes it flatter and wider.
Micro Structure of Tongue
Consists largely of skeletal muscle, partly invested by mucosa.
Lingual mucosa is thin interiorly, smooth. Mucosa at the pharyngeal part consists of many lymphoid follicles, containing rounded eminence, with a minute orifice of a funnel shaped recess. Many round / oval lymphoid nodules, each encapsulated by submucosa fibrosis, surround each recess which receives ducts of mucosa glands in the floor. Dorsal mucosa is thickest than ventral and lateral, adherent to muscular tissue & contains papillae. Consists of connective tissue (lamina propria) and stratified squamous epi covering papilla, consists of numerous nerves and vessels, large lympus plexuses and lingual glands. Epi varies from parakeratinized stratified squamous epi post to fully parasitized epi overlying the filiform papillal ant. Because the apex of tongue is subjected to greater dehydration than post and ventral parts and is more abraded during mastication.
Lingual Glands These are mucosa, serous and mixed types. Mucous glands are present at the post sulcul region. The anterior lingual salivery glands lie at the ventral surface of apex on each side of frenum, have muscular fascicules derivations from styloglossus and inferior longi muscles. These have mucous and serous alveoli and open by 3 -4 ducts on inferior surface of lingual apex.
Serous Glands (Von Ebnor) are present near the taste buds, are racemose in nature. Their secretion is watery assisting in gustation by spreading substances over the taste area.
Lingual Vessels and Nerves
Main artery is the lingual branch of ECA, Tonsillar and ascending palatine brs of facial and asceding pharyngeal A also supply. In the vallecula, epiglottis branches of superior laryngeal A anastomoses with inferior dorsal branches of Lingual A. Lingual mucouses are supplied by this rich network and also dense sub mucosal plexus.
Lingual veins follow two routes. Dorsal lingual vein drain the dorsum and sides of tongue and join the lingual vein accompanying the lingual A b/w hyoglossus & genioglossis.Near greater corner of hyoid bone they join the IJV.
Deep lingual begins near the tip, & runs back near the mucous memb on tongues inferior surface. Near the ant border of hyoglossus M it joins the sublingual V, runs back b/w mylohyoid and hyoglossus with hypoglossal N to join the facial, IJV or lingual V.
Lympatic peexus in lingual mucousa is continuos with an intra muscular plexus. The ant lingual region drains into the marginal and ventral vessels and. Lymphatic vessels are divided into marginal, lentral and dorsal.
a) Marginal Vessels They come from lingual apex and fremular region and descend under the mucousa to widely distributed nodes.
(i) Some pierce the mylohyoid in contact with mandibular periosteum to enter the submental nodes and also pass out to the hyoid bone to juglomohyoid node. Vessels arising from one side may cross under the fremulum to end in the contralateral nodes. Efferent vessels of submental nodes which are median pass to both sides.
(ii) Some vessels pierce the mylohyoid to enter the ant or middle submandibular nodes.
(iii) Some pass inferior to sublingual gland, accompany the hypoglossal N, end in juglo diagastric nodes. One often desends more deep to intermediate tendon of diagastric, to reach juglo omohyoid node.
(iv) Some vessels from the lateral lingual margin cross the sublingual gland, pierce the mylohyoid and end in submandibular nodes, others end in juglodiagastric or jugloomohyoid nodes.
Vessels from post part lingual margin transverse the pharyngeal wall to juglodiagastric lymph nodes.
1. Microglossia-rare congenital anomaly manifested by small or rudimentary tongue. Tongue totally absent is aglossia. Pateint has difficulty in eating and talking.
2. Macroglossia-Enlarged tongue. It can be congenital or secondary in type. Congnital is due to over musculature, might be associated with generalized muscular hypertrophy secondary macroglossia, haemengioua, neurobiromatosis, acromegaly. It produces displacement of teeth, malocclusion due to pressure exerted by tongue musculature. Presence of scalloping at lateral tongue margins. It’s a common feature in “beck with hypoglycomie syndrome” which in endues neonatal hypoglycemia, mild microcephaly, umbical nerves, fetal visceromegaly, post natal somatie giantism. There is no treatment for macroglossia except trimming the bulk.
3. Ankyloglossia-Complete ankygloossia occurs as a result of fusion b/w tongue and floor of mouth. Partial ankyglossia is called tongue lie as a result of short lingual frenum. Because of the restricted movements, there is difficulty in speech, esp pronunciation of certain consonants & diphthongs. Treated surgically by clipping the frenum.
4. Cleft Tongue or Bifid Tongue-Is a rare condition, due to lack of merging of lateral lingual swellings of this organ. Partial cleft tongue is more common, manifests as deep groove in midline of dorsal surface. It is due to incomplete merging and failure of groove obliteration by underlying mesenymal proliferation. Food depris gets collected here.
5. Fissured Tongue / Scrotal Tongue-Malformation clinically manifested by numerous small furrows or grooves on dorsal surface, radiating from central groove along midline. They are usually painless except where food debris gets collected to produce irritation.
6. Median Rhomboid Glossitis-Congenital anomaly due to failue of tuberculum impar to retract or withdraw before fusion of lateral valves of tongue so that a structure devoid of papillal is inter posed b/w them. It has etiologil relationship with candida albicans. It appears as ovoid, diamond shaped reddish patch or plaque on dorsal surface of tongue. A flat or slightly raised area. It has no filiform papillal. There is no specific treatment except antifungal drugs.
7. Benign Migratory Glossitis / Geographic Tongue-It has an unknown etiology, related to stress. Multiple areas desquamation of filiform papillal of tongue in irregular circinate pattern. It remains for a short time at that location, it heals and appear some where else. Heals / regress spontaneously and reoccurs later.
8. Hairy Tongue-There is hyper tropy of filiform papillal with lack of normal desquamation which may be extensive and form a thick matted layer on dorsal surface. Colour of papillal varies from yellow to even black. Due to extensive stains. Different micro org including candida albicans have been cultured from scrapings. Usage of oral drugs as Sodium peroxide, penicillin can also initiate this condition. Also seen in patients under going radio therapy.
9. Lingual Varies-Is a dilated, tortuous vein which is subjected to increased hydrostatic pressure but poorly supported by surrounding tissue. Lingual rapine veins are commonly involved.
10. Lingual Thyroid Nodule-Thyroid gland develops in embryo from ventral floor of pharynx by means of ecto dermal invagination. Tongue also forms at same time from this pharyngeal floor and is anatomically related to thyroid through thyroglossal tract, lingual remnant known as foramen calcum. In this follicles of thyroid gland are found in substance of tongue.
11. Carinoma Tongue, Is SCC-There are number of causes as chronic glossitis caused by syphilis. Lenco platia poor oral hygiene, chronic trauma, use of aslcohol & tobacco. Most common sign is painless ulcer which ultimately become painful when secondarily injected. It begins as superficial indverted ulcer with slightly raised borders, proceed to develop fumigating, exophytic mass or infiltrate to deep layers of tongue producing fixation and indviration without much surface change. It develops on lateral or ventral borders. Lesions at base of tongue may produce sore throat and dysphagia. Lesions at post part have greater chances of malignancy, metastasize earlier, have poor prognosis due to inaccessibility for treatment. Metastatic lesions may be epsilateral, bilateral, because of cross lymprated drainage. Surgery and radio therapy in combination are done. Prognosis of carcinoma at post 1/3 is not good.
12.Tongue in Various Diseases
(i) Scarlet Fever Streptococcal org causes, diffuse bright scarlet skin rash appears on 2nd or 3rd day particularly present in skin folds. Oral mucosa is referred to as “stomatits scarlatina”. Palate is congested, throat fiery red sometimes covered with grayish exudates. In early stage, tongue develops a white coating, filiform papillal are edematons and hyperemic projecting on surface as red knobs called as “strawberry tongue”. Coating is lost, lateral margins and tip are deep red in coronus, gustening and smooth. At this stage it is called as “raspberry tongue”.
(ii) Tuberculoses Lesion may occur at any site in oral cavity, by tongue is most common site followed by palate, lips and buccal mucosa. Lesion is irregular, superficarl or deep painful ulcer which tends to increase in size slowly, TB can involving the bone of maxilla or mandible.
(iii) Leprosy Oral lesions generally longest of small tumor like masses called lepromas which develop on tongue, lips and hard palate. These nodules have tendency to break down and ulcerate.
(iv) Candidiacies Caused by candida albicans. Caused in immuno compromised patients. It is of 4 types.
a) Acute psendomembraneous
b) Acute atropic
c) Chronic hyperplastic
d) curonic atropic
13. Tongue in Metabolic diseases
(i) Amyloidosis 2 types, Type A (secondary) amyloid is a fibrillar protein, seen in prolonged inflammatory diseases. Type B (Primary) amyloid of immune origin. Amyloid deposition in tongue gives rise to macroglossia.
(ii) VIP B Complex In Ribo flavil deficiency, there is glossitis which begins with soreness of tip of tongue to lateral margins. Filiform papillal become atropic, while fungiform remain normal or become enlarged and mushroom shaped giving tongue a reddened, coarsely, granular appearance. In niacin deficiency, patient complaint of burining tongue, which becomes swollen, press against teeth causing indentations. Tip and lateral margins of tongue become red.