Prenatal Craniofacial Development

Question 1

what are the ectodermal derivatives of cranial neural crest cells to craniofacial tissues

Answer 1

• epithelium of mouth/nose
• skin
• nervous system
• teeth
  -eye

Question 2

what are the mesodermal derivatives of the cranial neural crest cells for craniofacial tissues

Answer 2

-bone/cartilage
- fat
- muscle

Question 3

what are the endodermal derivatives of neural crest cells to craniofacial tissues

Answer 3

• respiratory tract
• GI tract: esophagus to rectum
• thyroid glands

Question 4

at 22 days, the head and neck region comprises ~ ___ of the embryo

Answer 4

half

Question 5

what happens to the pharyngeal arches during the 4th week

Answer 5

ventral mesoderm condenses into a series of segmented bilaterally paired mesenchymal swellings

Question 6

how many pairs of arches are there and in what order do they arise

Answer 6

• 5 pairs
• arise in cranial- caudal order

Question 7

what early prominences surround the stomodeum

Answer 7

• frontonasal prominence
• first arch (> mandibular process)
• maxillary process (delayed appearance

Question 8

which of the early prominences are paired structures

Answer 8

first arch and maxillary process

Question 9

how do the first arch and the maxillary process grow

Answer 9

ventro laterally around the oropharyngeal membrane (OM)

Question 10

what is the majority of the growth and morphological change in facial tissue mass driven by

Answer 10

the invading cranial neural crest derived mesenchyme

Question 11

the paired first pharyngeal arches only give rise to the ____

Answer 11

mandibular processes

Question 12

how do maxillary processes originate

Answer 12

as separate swellings rostral to the mandibular processes

Question 13

what are the nasal placodes

Answer 13

thickening of ectoderm

Question 14

where does formation and invagination of nasal placodes occur

Answer 14

in frontonasal prominence

Question 15

what is the induction and invagination of nasal placodes similar to

Answer 15

neural plate induction and invagination

Question 16

what are the two types of morphological processes for joining tissues and define each

Answer 16

• merging: joining of two masses already partly in contact
• fusion: joining of two separate tissue masses

Question 17

what happens in merging in morphogenesis of the midface

Answer 17

• merging of the maxillary and lateral nasal processes
• medial merging of mandibular processes

Question 18

what happens in fusion

Answer 18

-contact dependent fusion between MNP and MXP/LNP
- forms the primary plate and nares

Question 19

what does the secondary palate arise from

Answer 19

medial aspects of the MXPs > palatal shelves

Question 20

what is growth and morphogenesis of the face controlled by after the immigration of cranial neural crest cells

Answer 20

ongoing epithelial- mesenchyme interactions

Question 21

what primarily determine facial form/shape

Answer 21

cranial neural crest cells

Question 22

what is the function of the ectoderm

Answer 22

• support and direct outgrowth of the facial processes
• guides differentiation of CNC
• facilitating timely fusion of the facial processes

Question 23

what does the primary plate go on to form

Answer 23

the alveolus and lip proper

Question 24

what does the secondary palate go on to form

Answer 24

the roof of the mouth

Question 25

what is full fusion required for

Answer 25

to ensure the alveolar bone is continuous

Question 26

what is the third most common birth defect

Answer 26

cleft lip +/- cleft primary palate

Question 27

what are the palatal shelves a result of

Answer 27

condensations of CNCC mesenchyme

Question 28

when does the primary palate form? secondary palate?

Answer 28

primary: 7th secondary: 10th

Question 29

when does ossification of the secondary palate begin

Answer 29

just before palatal development completes

Question 30

describe growth of the secondary palate

Answer 30

-growth either side of tongue - elevation and rotation - medial growth and fusion at midline and with nasal septum

Question 31

what is the incidence of cleft secondary palate

Answer 31

1 in 1000 briths

Question 32

what can cleft secondary palate result from

Answer 32

- poor growth of shelves - failed elevation - failed fusion

Question 33

describe the interaction between the tongue and secondary palate closure

Answer 33

- critical that the tongue lowers to allow the shelves to rotate to a position above the tongue

Question 34

what is the effect of macroglossia on secondary palate closure

Answer 34

provides a physical barrier

Question 35

what disorder of the mandible can be associated with failed palatal fusion

Answer 35

small or retrognathic mandible- pierre robin sequence - causes the tongue to be forced backward and elevated

Question 36

where does the craniofacial cartilage first appear

Answer 36

in the mandible and shortly thereafter in the midface and cranial base

Question 37

what is the function of the craniofacial cartilage

Answer 37

structural support for shaping the growing head

Question 38

what does the formation of craniofacial cartilage precede

Answer 38

ossification

Question 39

when does meckels cartilage appear and what arch is it in and what does it form

Answer 39

- during 7th week - Pharyngeal arch 1 - forms template for the mandible

Question 40

what else does PA1 also contribute to besides meckels cartilage

Answer 40

two ear ossicles- malleus and incus

Question 41

since most facial cartilages are not converted to bone what happens instead

Answer 41

parts degenerate with caudal aspects forming part of middle ear bones

Question 42

what is the ear formed by

Answer 42

independent embryonic structures

Question 43

describe the development of the external and middle ear

Answer 43

- derivatives of PA1 and PA2 - intervening pharyngeal cleft - pharyngeal pouch

Question 44

what does the inner ear arise from

Answer 44

thickening of ectoderm (otic placode) dorsal to PA3 at level of hindbrain and subsequent invagination (otic pit)

Question 45

what are inner and outer ear malformations often associated with

Answer 45

mandibular defects