MEDICO EXPRESS BLOCK 4 BOOK 1
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Medico Express
BLOCK 4
GIT AND NUTRITION- I MODULE
EMBRYOLOGY
GIT- Describe the development of tongue Embryology Oral
A-014 Describe the embryological basis of tongue tie Cavity
Describe the development of palate
Describe the embryological basis of various
facial clefts Identify the parts of the
developing tongue and palate
Development of the Tongue
1. Formation of the Tongue Buds (End of Fourth Week):
o A median lingual swelling (tongue bud) appears in the floor of
the primordial pharynx, just rostral to the foramen cecum.
o Two lateral lingual swellings (distal tongue buds) develop on
each side of the median swelling from mesenchyme in the
ventromedial parts of the first pharyngeal arches.
2. Merging of the Swellings:
o The lateral lingual swellings rapidly increase in size, merge, and
overgrow the median lingual swelling.
o This fusion forms the anterior two-thirds of the tongue (oral
part), marked by a midline groove and the fibrous lingual
septum.
,MEDICO EXPRESS BLOCK 4 BOOK 2
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3. Formation of the Posterior Third:
o The posterior third of the tongue (pharyngeal part) arises from:
The copula (fused ventromedial parts of the second
pharyngeal arches).
The hypopharyngeal eminence (from the third and
fourth pharyngeal arches).
o The hypopharyngeal eminence gradually overgrows the copula,
contributing to the posterior third.
4. Fusion Line:
o The fusion between the anterior and posterior parts is indicated
by the terminal sulcus, a V-shaped groove.
5. Muscle Development:
o Most tongue muscles derive from myoblasts migrating from the
second to fifth occipital myotomes, innervated by the
hypoglossal nerve (CN XII).
6. Nerve Supply:
o Anterior Two-Thirds: Sensory supply from the lingual branch of
the mandibular division of the trigeminal nerve (CN V); taste
from the chorda tympani of the facial nerve (CN VII).
o Posterior Third: Mainly innervated by the glossopharyngeal
nerve (CN IX); a small area anterior to the epiglottis by the
superior laryngeal branch of the vagus nerve (CN X).
o All tongue muscles are innervated by the hypoglossal nerve,
except for the palatoglossus, supplied by the pharyngeal plexus
(CN X).
,MEDICO EXPRESS BLOCK 4 BOOK 3
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7. Lingual Papillae Development (Eighth Week):
o Vallate and foliate papillae develop first, followed by fungiform
papillae.
o Filiform papillae appear during the early fetal period (10–11
weeks).
8. Taste Bud Formation (Weeks 11-13):
o Taste buds develop from interactions between tongue epithelial
cells and gustatory nerve cells from the chorda tympani,
glossopharyngeal, and vagus nerves.
o Most taste buds form on the dorsal surface of the tongue, with
some on the palate, epiglottis, and oropharynx.
Embryological Basis of Ankyloglossia (Tongue-Tie)
1. Lingual Frenulum Formation:
o The lingual frenulum connects the tongue's inferior surface to
the floor of the mouth, forming from mesenchyme in the
ventromedial parts of the first pharyngeal arch.
2. Short Frenulum Development:
o Ankyloglossia occurs when the frenulum is abnormally short,
extending to the tip of the tongue, due to incomplete or
abnormal development during embryogenesis.
3. Functional Impact:
o A short frenulum restricts tongue mobility, potentially affecting
breastfeeding, though it usually has no significant long-term
consequences.
4. Postnatal Changes:
o The short frenulum often stretches over time, making surgical
correction unnecessary in many cases.
, MEDICO EXPRESS BLOCK 4 BOOK 4
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Development of the Palate
o The palate develops from two primordia: the primary and
secondary palates.
o Palatogenesis begins in the sixth week and is completed by the
twelfth week, regulated by molecular pathways like WNT and
PRICKLE1.
2. Critical Period:
o End of the sixth week to the beginning of the ninth week.
3. Primary Palate:
o Begins forming in the sixth week from the merging of the medial
nasal prominences.
o It is a wedge-shaped mass of mesenchyme between the internal
surfaces of the maxillary prominences.
o The primary palate forms the anterior and midline aspect of the
maxilla, contributing to the premaxillary part of the maxilla,
which becomes a small part of the adult hard palate.
4. Secondary Palate:
o The secondary palate, or definitive palate, develops from lateral
palatine processes (palatal shelves) extending from the maxillary
prominences.
o Initially, these processes project inferomedially on each side of
the tongue.
o As the jaws elongate, the tongue is pulled away, allowing the
lateral palatine processes to assume a horizontal position above
the tongue during the seventh and eighth weeks.
Follow Medico Expresss E learning on instagram
Medico Express
BLOCK 4
GIT AND NUTRITION- I MODULE
EMBRYOLOGY
GIT- Describe the development of tongue Embryology Oral
A-014 Describe the embryological basis of tongue tie Cavity
Describe the development of palate
Describe the embryological basis of various
facial clefts Identify the parts of the
developing tongue and palate
Development of the Tongue
1. Formation of the Tongue Buds (End of Fourth Week):
o A median lingual swelling (tongue bud) appears in the floor of
the primordial pharynx, just rostral to the foramen cecum.
o Two lateral lingual swellings (distal tongue buds) develop on
each side of the median swelling from mesenchyme in the
ventromedial parts of the first pharyngeal arches.
2. Merging of the Swellings:
o The lateral lingual swellings rapidly increase in size, merge, and
overgrow the median lingual swelling.
o This fusion forms the anterior two-thirds of the tongue (oral
part), marked by a midline groove and the fibrous lingual
septum.
,MEDICO EXPRESS BLOCK 4 BOOK 2
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3. Formation of the Posterior Third:
o The posterior third of the tongue (pharyngeal part) arises from:
The copula (fused ventromedial parts of the second
pharyngeal arches).
The hypopharyngeal eminence (from the third and
fourth pharyngeal arches).
o The hypopharyngeal eminence gradually overgrows the copula,
contributing to the posterior third.
4. Fusion Line:
o The fusion between the anterior and posterior parts is indicated
by the terminal sulcus, a V-shaped groove.
5. Muscle Development:
o Most tongue muscles derive from myoblasts migrating from the
second to fifth occipital myotomes, innervated by the
hypoglossal nerve (CN XII).
6. Nerve Supply:
o Anterior Two-Thirds: Sensory supply from the lingual branch of
the mandibular division of the trigeminal nerve (CN V); taste
from the chorda tympani of the facial nerve (CN VII).
o Posterior Third: Mainly innervated by the glossopharyngeal
nerve (CN IX); a small area anterior to the epiglottis by the
superior laryngeal branch of the vagus nerve (CN X).
o All tongue muscles are innervated by the hypoglossal nerve,
except for the palatoglossus, supplied by the pharyngeal plexus
(CN X).
,MEDICO EXPRESS BLOCK 4 BOOK 3
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7. Lingual Papillae Development (Eighth Week):
o Vallate and foliate papillae develop first, followed by fungiform
papillae.
o Filiform papillae appear during the early fetal period (10–11
weeks).
8. Taste Bud Formation (Weeks 11-13):
o Taste buds develop from interactions between tongue epithelial
cells and gustatory nerve cells from the chorda tympani,
glossopharyngeal, and vagus nerves.
o Most taste buds form on the dorsal surface of the tongue, with
some on the palate, epiglottis, and oropharynx.
Embryological Basis of Ankyloglossia (Tongue-Tie)
1. Lingual Frenulum Formation:
o The lingual frenulum connects the tongue's inferior surface to
the floor of the mouth, forming from mesenchyme in the
ventromedial parts of the first pharyngeal arch.
2. Short Frenulum Development:
o Ankyloglossia occurs when the frenulum is abnormally short,
extending to the tip of the tongue, due to incomplete or
abnormal development during embryogenesis.
3. Functional Impact:
o A short frenulum restricts tongue mobility, potentially affecting
breastfeeding, though it usually has no significant long-term
consequences.
4. Postnatal Changes:
o The short frenulum often stretches over time, making surgical
correction unnecessary in many cases.
, MEDICO EXPRESS BLOCK 4 BOOK 4
Follow Medico Expresss E learning on instagram
Development of the Palate
o The palate develops from two primordia: the primary and
secondary palates.
o Palatogenesis begins in the sixth week and is completed by the
twelfth week, regulated by molecular pathways like WNT and
PRICKLE1.
2. Critical Period:
o End of the sixth week to the beginning of the ninth week.
3. Primary Palate:
o Begins forming in the sixth week from the merging of the medial
nasal prominences.
o It is a wedge-shaped mass of mesenchyme between the internal
surfaces of the maxillary prominences.
o The primary palate forms the anterior and midline aspect of the
maxilla, contributing to the premaxillary part of the maxilla,
which becomes a small part of the adult hard palate.
4. Secondary Palate:
o The secondary palate, or definitive palate, develops from lateral
palatine processes (palatal shelves) extending from the maxillary
prominences.
o Initially, these processes project inferomedially on each side of
the tongue.
o As the jaws elongate, the tongue is pulled away, allowing the
lateral palatine processes to assume a horizontal position above
the tongue during the seventh and eighth weeks.
