Development of tongueDevelopment of tongue

• Begins in 4 week Begins in 4 week • 11stst and 2 and 2ndnd branchial arches meet in the branchial arches meet in the

midline beneath the stomadeummidline beneath the stomadeum• The mesenchyme of the 1The mesenchyme of the 1stst

P.ARCH( Mand arch) proliferate to form a P.ARCH( Mand arch) proliferate to form a midline swelling the TUBERCULUMIMPAR midline swelling the TUBERCULUMIMPAR flanked by the other two lingual flanked by the other two lingual swellingsswellings

• Hypobranchial eminence is the midline Hypobranchial eminence is the midline swelling that appears in the 3swelling that appears in the 3rdrd arch, arch, developes from the mesenchyme of the developes from the mesenchyme of the 33rdrd arch. arch.

• The 2The 2ndnd arch is excluded from further arch is excluded from further development of the tongue by development of the tongue by overgrowth of mesenchyme of 3overgrowth of mesenchyme of 3rdrd arch arch over 2over 2ndnd arch. arch.

• The 1The 1stst and 2 and 2ndnd arches meetin the arches meetin the midline beneath the primitive mouth midline beneath the primitive mouth while the remaining arches fail to meet while the remaining arches fail to meet & a gap between them is filled with the & a gap between them is filled with the sweeling called Hypobranchial eminence sweeling called Hypobranchial eminence ( Copula)( Copula)

• A 3A 3rdrd median swelling called epiglottal median swelling called epiglottal swelling ( from 4rth arch) marks the swelling ( from 4rth arch) marks the development of epiglottis.development of epiglottis.

Mucosa of tongueMucosa of tongue• Mucosa of ant 2/3Mucosa of ant 2/3rdrd of the tongue of the tongue • The lateral lingual swellings enlarge and merge The lateral lingual swellings enlarge and merge

with each other and the tuberculum impar to with each other and the tuberculum impar to form a large mass from which the mucosa of form a large mass from which the mucosa of the ant 2/3the ant 2/3rdrd of the tongue is formed. of the tongue is formed.

• Post 1/3Post 1/3rdrd develops from a single large midline develops from a single large midline swelling, the copula which is mainly derived swelling, the copula which is mainly derived from the 3from the 3rdrd arch with a small contribution from arch with a small contribution from 4rth arch.The copula overgrows the 24rth arch.The copula overgrows the 2ndnd arch to arch to merge with the 1merge with the 1stst arch swelling to give rise to arch swelling to give rise to the mucosa of post 2/3the mucosa of post 2/3rdrd..

• The thyroid gland develops between the The thyroid gland develops between the tuberculum impar and the Hypobrachial tuberculum impar and the Hypobrachial eminence(copula).On a fully formed eminence(copula).On a fully formed tongue this site is demarcated by a tongue this site is demarcated by a small pit , Foramen Caecum.small pit , Foramen Caecum.

• Line of fusion between the Copula and Line of fusion between the Copula and the ant 2/3the ant 2/3rdrd of the tongue is the sulcus of the tongue is the sulcus terminalis whose apex is the F Caecum.terminalis whose apex is the F Caecum.

Taste budsTaste buds• Arise by inductive interaction between Arise by inductive interaction between

epithelial cells and invading gustatory nerve epithelial cells and invading gustatory nerve cels from chorda tympani ( facial), cels from chorda tympani ( facial), glosopharyngeal and vagus nerves.glosopharyngeal and vagus nerves.

• Taste bud formation occurs greatest conc in Taste bud formation occurs greatest conc in dorsal surface of tongue and in lesser numbers dorsal surface of tongue and in lesser numbers on the palatoglossal arches , palate, post on the palatoglossal arches , palate, post surface of epiglottis posr wall of oropharynx.surface of epiglottis posr wall of oropharynx.

• Gustatory cell formation commences as early Gustatory cell formation commences as early as 7as 7thth week I.U but recognisable taste buds do week I.U but recognisable taste buds do not form until 13- 15 week IU.not form until 13- 15 week IU.

PapillaePapillae• Circumvallate papillae – Found adjacent and Circumvallate papillae – Found adjacent and

anterior to sulcul teminalis, develop 2 to 5 anterior to sulcul teminalis, develop 2 to 5 months of I.U.months of I.U.

• Fungi form papillae-Mushroom shaped, ant Fungi form papillae-Mushroom shaped, ant portion of the tongue, develope 11 weeks .I.uportion of the tongue, develope 11 weeks .I.u

• Filiform- Cone shaped- cover entire ant part of Filiform- Cone shaped- cover entire ant part of the tongue ;develop post natally the tongue ;develop post natally

• Foliate papillae- Leaf like- lateral margins of Foliate papillae- Leaf like- lateral margins of post tonguepost tongue

• Taste buds in C . Papillae develop Taste buds in C . Papillae develop post nataly,in Fungiform papillae at post nataly,in Fungiform papillae at birth, fungi form in fetal life. No birth, fungi form in fetal life. No taste buds in filiform papillae.taste buds in filiform papillae.

Muscles of the tongueMuscles of the tongue• Arise from the occipital somites Arise from the occipital somites

which have migrated forwards to which have migrated forwards to the tongue area into the floor of the tongue area into the floor of the mouth carrying with them the the mouth carrying with them the hypoglossal Nerve.hypoglossal Nerve.

Nerve supplyNerve supply• Mucosa of the anterior 2/3Mucosa of the anterior 2/3rdrd of the of the

tongue- 1tongue- 1stst arch- V N arch- V N• Mucosa of post tongue- 3Mucosa of post tongue- 3rdrd arch- arch-

Glossopharyngeal nerve IX N Glossopharyngeal nerve IX N • Anterior 2/3Anterior 2/3rdrd gustatory- Chorda gustatory- Chorda

tympany a branch of VII N – 2tympany a branch of VII N – 2ndnd ArchArch

Lingual TonsilLingual Tonsil• At Birth the mucosa of the root of At Birth the mucosa of the root of

the tongue becomes pitted by deep the tongue becomes pitted by deep crypts, lymphocytic infiltration- crypts, lymphocytic infiltration- Lingual tonsil.Lingual tonsil.

Thyroid glandThyroid gland• Thyroid promordium arises as an epithelial Thyroid promordium arises as an epithelial

diverticulum I the midline of the pharynx, diverticulum I the midline of the pharynx, caudal to T Impar, F Caecum area.caudal to T Impar, F Caecum area.

• Subsequently the thyroid descends in front Subsequently the thyroid descends in front of the pharyngeal gut as a bilobed of the pharyngeal gut as a bilobed diverticulum.diverticulum.

• During this migration the gland remains During this migration the gland remains connected to the tongue by a narrow canal connected to the tongue by a narrow canal , Thyroglaossal duct, later becomes solid , Thyroglaossal duct, later becomes solid and disappears.and disappears.

• Thyroglossal cysts and fistula may be Thyroglossal cysts and fistula may be found at anypoint along the migration found at anypoint along the migration path fillowed by the thyroid gland.Cystic path fillowed by the thyroid gland.Cystic remanants- thyroglossal cysts.remanants- thyroglossal cysts.

• Thyroglossal fistula- after rupture of a Thyroglossal fistula- after rupture of a cyst, or mey be present at birthcyst, or mey be present at birth

• Abberant thyroid tissue- may be found Abberant thyroid tissue- may be found anywhere along the path of the descent anywhere along the path of the descent of thyroid gland.commonly at the base of thyroid gland.commonly at the base of the tongue just behind the F Caecum.of the tongue just behind the F Caecum.

AnomaliesAnomalies• Microglossia- abnormally small tongue, Microglossia- abnormally small tongue,

fail to achieve a normal growth rate.fail to achieve a normal growth rate.• Macroglossia- over developmentMacroglossia- over development• Aglossia- tongue fails to developAglossia- tongue fails to develop• Bifid, Trifid, Forked tongue- Filure of Bifid, Trifid, Forked tongue- Filure of

fusion of its components.fusion of its components.

Ankyloglossia- Tongue tieAnkyloglossia- Tongue tie

• Tongue is not freed from the FOM , Tongue is not freed from the FOM , frenulum extents to the tip of the frenulum extents to the tip of the tongue; Normally extensive cell tongue; Normally extensive cell degeneration occurs and frenulumis the degeneration occurs and frenulumis the only tissue persisting tying the tongue to only tissue persisting tying the tongue to the FOM. the FOM.