Development of the Tongue, Face, and Nose

Question 1

neural crest cells are essential for

Answer 1

formation of much of the craniofacial region
formation of conotruncal endocardial cushions

Question 2

craniofacial defects and cardiac anomalies are from

Answer 2

insufficient migration of neural crest cells into the pharyngeal arches
cardiac abnormalities like persistent truncus arteriosus, teratology of fallot and transposition of great vessels

Question 3

crest cells are particularly vulnerable to

Answer 3

compounds such as alcohol and retinoic acid (Vitamin A)

Question 4

treacher collins syndrome TCS (mandibulofacial dysostosis)

Answer 4

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)

Question 5

diGeorge syndrome (3rd and 4th arches)

Answer 5

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

Question 6

what does CATCH stand for

Answer 6

C ardiac defects
A bnormal facies
T hymic hypoplasia
C left palate
H ypocalcemia

Question 7

anatomy of the tongue

Answer 7

tongue is divided into anterior 2/3 and posterior 1/3

Question 8

innervation of the tongue

Answer 8

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

Question 9

development of the tongue

Answer 9

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

Question 10

anomalies of the tongue

Answer 10

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

Question 11

anatomy of the thyroid gland

Answer 11

shield shaped gland with right and left lobes connected by a central isthmus

isthmus lies anterior to the second and third tracheal rings

Question 12

thyroid gland

Answer 12

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

Question 13

thyroid anomalies

Answer 13

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)

Question 14

formation of the face: SHH and forebrain

Answer 14

migration of the neural crest cells major source for cartilage, bone and ligaments of the face

Question 15

five processes around the stomodeum and develop from where

Answer 15

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

Question 16

nasal placodes –> nasal pit –> nasal cavity

Answer 16

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

Question 17

frontonasal prominence forms

Answer 17

forehead and the dorsum till apex of the nose
lateral nasal prominences: sides of the nose
medial nasal prominences: philtrum, nasal septum

Question 18

maxillary prominences forms

Answer 18

upper cheek region and most of the upper lip

Question 19

mandibular prominences forms

Answer 19

chin, lower lip, and lower cheek regions

Question 20

muscles of the facial expression formed by

Answer 20

migration of the mesenchyme from the Second Pharyngeal arch and are supplied by the facial nerve

Question 21

what is the nasolacrimal duct

Answer 21

a normal duct that interconnects the eye and the nose
it drains excess lacrimal fluid to the nose

Question 22

how is the nasolacrimal duct formed

Answer 22

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

Question 23

oblique facial cleft

Answer 23

anomaly due to failure of maxillary prominences to merge with its corresponding lateral nasal prominences

Question 24

in patients with an oblique facial cleft the _______ ______ remains exposed, along with a _____ lip

Answer 24

nasolacrimal duct
cleft

Question 25

formation of upper lip

Answer 25

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

Question 26

development of palate

Answer 26

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

Question 27

development of palate

Answer 27

1. secondary palate: forms from outgrowths from the maxillary process - palatine shelves
2. the post natal hard palate develops from the fusion of the right and left palatine shelves and intermaxillary segment
3. 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

Question 28

formation of nasal septum

Answer 28

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

Question 29

summary of the development of palate

Answer 29

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