Development of the Tongue, Face, and Nose Flashcards
neural crest cells are essential for
formation of much of the craniofacial region
formation of conotruncal endocardial cushions
craniofacial defects and cardiac anomalies are from
insufficient migration of neural crest cells into the pharyngeal arches
cardiac abnormalities like persistent truncus arteriosus, teratology of fallot and transposition of great vessels
crest cells are particularly vulnerable to
compounds such as alcohol and retinoic acid (Vitamin A)
treacher collins syndrome TCS (mandibulofacial dysostosis)
hypoplasia of maxilla, mandible and zygomatic bones
external ear defects, atresia of auditory canals and abnormality of middle ear ossicles with conductive hearing loss
open bite, reduced number of teeth
abnormality of dental enamel and dental morphology
TCOF1 gene mutation in most cases (gene produces Treacle protein necessary for preventing apoptosis and maintaining proliferation in neural crest cells)
diGeorge syndrome (3rd and 4th arches)
collection of disorders, due to chromosomal anomaly 22q11.2
forms a spectrum called CATCH 22
defect in the migration of neural crest cells to the craniofacial region
what does CATCH stand for
C ardiac defects
A bnormal facies
T hymic hypoplasia
C left palate
H ypocalcemia
anatomy of the tongue
tongue is divided into anterior 2/3 and posterior 1/3
innervation of the tongue
anterior 2/3 from branches of mandibular nerve (lingual branch) and facial nerve (chorda tympani branch)
posterior 1/3 from glossopharyngeal and superior laryngeal branch of Vagus
development of the tongue
in the primordial pharynx from the first and second pharyngeal arches
a median lingual swelling is formed
followed by two lateral lingual swellings
lateral lingual swelling grow rapidly and merge to form the anterior 2/3 of the tongue (oral part)
site of fusion of these two is marked by the midline groove on the tongue even after birth
posterior 1/3 of the tongue develops from the hypobranchial eminence formed from the 3rd and 4th pharyngeal arches
anomalies of the tongue
ankyloglossia (tongue tie): lingual frenulum connects inferior surface of the tongue to the floor of the mouth, short frenulm, extending to the tip of the tongue
incomplete fusion of lateral lingual swellings: bifid/Cleft tongue
macroglossia and microglossia: abnormally large or small tongue
anatomy of the thyroid gland
shield shaped gland with right and left lobes connected by a central isthmus
isthmus lies anterior to the second and third tracheal rings
thyroid gland
proliferation of endoderm from the floor of the pharynx
arises at the foramen cecum (persists in postnatal life)
descends in front of the pharyngeal gut as bilobed diverticulum
initially remains, connected to tongue by a canal - thyroglossal duct, but it must disintegrate
thyroid anomalies
thyroglossal cyst: anywhere along the migratory pathway the remnant of the duct may produce cyst, may be connected to the outside (thyroglossal fistula)
aberrant thyroid tissue: may be found anywhere along the path descent, commonly found in the base of the tongue behind the foramen cecum (lingual thyroid)
formation of the face: SHH and forebrain
migration of the neural crest cells major source for cartilage, bone and ligaments of the face
five processes around the stomodeum and develop from where
frontonasal process from the mesoderm covering the forebrain
a pair of maxillary processes
a pair of mandibular processes
develop from the 1st and 2nd pharyngeal arches
nasal placodes –> nasal pit –> nasal cavity
nasal placodes (nasal epithelium) - thickening of the ectoderm
margins of the placodes proliferated to form medial and lateral nasal prominences
formation of nasal pits which deepen to form the nostrils and nasal cavities
frontonasal prominence forms
forehead and the dorsum till apex of the nose
lateral nasal prominences: sides of the nose
medial nasal prominences: philtrum, nasal septum
maxillary prominences forms
upper cheek region and most of the upper lip
mandibular prominences forms
chin, lower lip, and lower cheek regions
muscles of the facial expression formed by
migration of the mesenchyme from the Second Pharyngeal arch and are supplied by the facial nerve
what is the nasolacrimal duct
a normal duct that interconnects the eye and the nose
it drains excess lacrimal fluid to the nose
how is the nasolacrimal duct formed
maxillary and lateral nasal prominences merge to establish continuity between the side of the nose and the cheek
they are initially separated by nasolacrimal groove
the groove invaginated to produce the nasolacrimal duct
oblique facial cleft
anomaly due to failure of maxillary prominences to merge with its corresponding lateral nasal prominences
in patients with an oblique facial cleft the _______ ______ remains exposed, along with a _____ lip
nasolacrimal duct
cleft
formation of upper lip
philtrum (central) part: merging of the two medial nasal prominences
lateral parts: two maxillary prominences
merged medial nasal processes also contribute to the formation of the primary palate
development of palate
intermaxillary segment: fusion of the 2 medial nasal prominences
develops into 3 post natal segments:
labial - philtrum of upper lip
upper jaw - 4 incisor teeth
palatine - primary palate
development of palate
- secondary palate: forms from outgrowths from the maxillary process - palatine shelves
- the post natal hard palate develops from the fusion of the right and left palatine shelves and intermaxillary segment
- the junction between the primary and the secondary palate (which develop from two different sources) is marked in post natal life by the incisive foramen
formation of nasal septum
superiorly from the roof of the nasal cavity a downward growing nasal septum fuses with the palatine shelves to give rise to the postnatal pattern of two nasal cavities and an oral cavity
summary of the development of palate
primitive (primary) palate
- formed by merged median nasal processes
- develops into a wedge-shaped area in front of the incisive fossa and carries the four incisor teeth
secondary palate
- shelf like projections from the maxillary processes: palatine shelves
