prenatal craniofacial development

Question 1

what happens during the 4th week

Answer 1

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

Question 2

initially FIVE prominences (tissue masses) surround the stomodeum
these are

Answer 2

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

Question 3

first (mandibular) arch and maxillary processes are both paired structures that grow

Answer 3

ventro-laterally around the OM (oropharyngeal membrane aka back of the mouth)

Question 4

the majority of the growth and morphological change in facial tissue masses is driven by the invading

Answer 4

cranial neural crest-derived mesenchyme

Question 5

maxillary processes originate

Answer 5

as separate (delayed) swellings rostral to the mandibular processes

invaded by distinct population of late migrating CNCC

Question 6

the thickening of ectoderm in FNP (frontonasal prominence)

Answer 6

nasal placodes

Question 7

two types of morphological processes for joining tissues

Answer 7

1. merging: joining of two masses already partly in contact
2. fusion: joining of two separate masses

Question 8

two examples of merging

Answer 8

1. merging of maxillary (MXP) and lateral nasal processes (LNP)
2. medial merging of mand (MNP)

Question 9

two examples of fusion

Answer 9

contact dependent fusion between MNP and MXP/LNP

MNP with MNP
MNP with MXP
MNP with LNP

Question 10

another fusion event is with the secondary palate (future roof of mouth) during 10th week which arises later from the

Answer 10

medial aspects of the MXP >palatal shelves

(fusion event)

Question 11

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

Answer 11

ongoing epithelial-mesenchymal interactions

(controlled independently)

Question 12

these cells primarily determine facial form/shape

Answer 12

cranial neural crest cells

Question 13

neural expression of ______ precedes and required for the ectodermal expression

Answer 13

Shh/Fgf8

Shh= ventral facial ectoderm
Fgf8= dorsal facial ectoderm

Question 14

secreted factors from the ____ can direct outgrowth of the underlying CNCC and determines D-V pattern of FNP.
But precise shape depends upon pattern information inherent in the _______

Answer 14

frontonasal ectoderm zone (FEZ)

neural crest

Question 15

the ectoderm has a role and supports/directs =
and guides=
and facilitates=

Answer 15

outgrowth of the facial processes and
guides differentiation of CNC
and facilitates timely fusion of the facial processes

Question 16

when does secondary palate form

Answer 16

10th week

(forms well after the primary palate/lip) 7th week

Question 17

what determines secondary palate formation:
1
2
3

Answer 17

1. growth (either side of the tongue)
2. elevation and rotation
3. medial growth and fusion at midline with nasal septum

Question 18

ossification of the secondary palate (osteoblasts derived from CNCC) begins

Answer 18

just before palatal development complete

Question 19

what is the secondary palate

Answer 19

palatal shelves (condensations of CNCC mesenchyme)

Question 20

how can cleft secondary palate result from

Answer 20

1. poor growth of shelves
2. failed elevation
3. failed fusion

Question 21

what is critical to allow the shelves to rotate to a position above the tongue

Answer 21

tongue lowers

Question 22

this can provide a physical barrier to secondary palate closure

Answer 22

macroglossia

Question 23

this also is associated with failed palatal fusion where the tongue sits too far back aka tongue forced backwards and elevated

Answer 23

small or retrognathic mandible

Question 24

this first appears in the mandible and shortly thereafter in the midface and cranial base. provides structural support for shaping the growing head!

Answer 24

craniofacial cartilage

Question 25

leads up to aka precedes ossification

Answer 25

craniofacial cartilage
[in the face, few cartilages are replaced by bone unlike the axial skeletion]

Question 26

the cartilage of PA1 that arises during week 7 and forms the template for mandible

Answer 26

meckel’s cartilage

Question 27

PA1 also contributes to two ear ossicles which are parts of

Answer 27

malleus and incus

Question 28

since most facial cartilages are not converted to bone, but rather parts degenerate with caudal aspects forming what part

Answer 28

part of middle ear bones

Question 29

what is the ear formed from

Answer 29

independent embryonic structures

Question 30

external and middle are derivatives of:

Answer 30

PA1 and PA2
-intervening pharyngeal CLEFT and pharyngeal POUCH

Question 31

inner ear arise from

Answer 31

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

Question 32

inner and outer ear malformations often associate with

Answer 32

mandibular defects