Prenatal Craniofacial Development Flashcards
what are the ectodermal derivatives of cranial neural crest cells to craniofacial tissues
- epithelium of mouth/nose
- skin
- nervous system
- teeth
-eye
what are the mesodermal derivatives of the cranial neural crest cells for craniofacial tissues
-bone/cartilage
- fat
- muscle
what are the endodermal derivatives of neural crest cells to craniofacial tissues
- respiratory tract
- GI tract: esophagus to rectum
- thyroid glands
at 22 days, the head and neck region comprises ~ ___ of the embryo
half
what happens to the pharyngeal arches during the 4th week
ventral mesoderm condenses into a series of segmented bilaterally paired mesenchymal swellings
how many pairs of arches are there and in what order do they arise
- 5 pairs
- arise in cranial- caudal order
what early prominences surround the stomodeum
- frontonasal prominence
- first arch (> mandibular process)
- maxillary process (delayed appearance
which of the early prominences are paired structures
first arch and maxillary process
how do the first arch and the maxillary process grow
ventro laterally around the oropharyngeal membrane (OM)
what is the majority of the growth and morphological change in facial tissue mass driven by
the invading cranial neural crest derived mesenchyme
the paired first pharyngeal arches only give rise to the ____
mandibular processes
how do maxillary processes originate
as separate swellings rostral to the mandibular processes
what are the nasal placodes
thickening of ectoderm
where does formation and invagination of nasal placodes occur
in frontonasal prominence
what is the induction and invagination of nasal placodes similar to
neural plate induction and invagination
what are the two types of morphological processes for joining tissues and define each
- merging: joining of two masses already partly in contact
- fusion: joining of two separate tissue masses
what happens in merging in morphogenesis of the midface
- merging of the maxillary and lateral nasal processes
- medial merging of mandibular processes
what happens in fusion
-contact dependent fusion between MNP and MXP/LNP
- forms the primary plate and nares
what does the secondary palate arise from
medial aspects of the MXPs > palatal shelves
what is growth and morphogenesis of the face controlled by after the immigration of cranial neural crest cells
ongoing epithelial- mesenchyme interactions
what primarily determine facial form/shape
cranial neural crest cells
what is the function of the ectoderm
- support and direct outgrowth of the facial processes
- guides differentiation of CNC
- facilitating timely fusion of the facial processes
what does the primary plate go on to form
the alveolus and lip proper
what does the secondary palate go on to form
the roof of the mouth
what is full fusion required for
to ensure the alveolar bone is continuous
what is the third most common birth defect
cleft lip +/- cleft primary palate
what are the palatal shelves a result of
condensations of CNCC mesenchyme
when does the primary palate form? secondary palate?
primary: 7th
secondary: 10th
when does ossification of the secondary palate begin
just before palatal development completes
describe growth of the secondary palate
-growth either side of tongue
- elevation and rotation
- medial growth and fusion at midline and with nasal septum
what is the incidence of cleft secondary palate
1 in 1000 briths
what can cleft secondary palate result from
- poor growth of shelves
- failed elevation
- failed fusion
describe the interaction between the tongue and secondary palate closure
- critical that the tongue lowers to allow the shelves to rotate to a position above the tongue
what is the effect of macroglossia on secondary palate closure
provides a physical barrier
what disorder of the mandible can be associated with failed palatal fusion
small or retrognathic mandible- pierre robin sequence
- causes the tongue to be forced backward and elevated
where does the craniofacial cartilage first appear
in the mandible and shortly thereafter in the midface and cranial base
what is the function of the craniofacial cartilage
structural support for shaping the growing head
what does the formation of craniofacial cartilage precede
ossification
when does meckels cartilage appear and what arch is it in and what does it form
- during 7th week
- Pharyngeal arch 1
- forms template for the mandible
what else does PA1 also contribute to besides meckels cartilage
two ear ossicles- malleus and incus
since most facial cartilages are not converted to bone what happens instead
parts degenerate with caudal aspects forming part of middle ear bones
what is the ear formed by
independent embryonic structures
describe the development of the external and middle ear
- derivatives of PA1 and PA2
- intervening pharyngeal cleft
- pharyngeal pouch
what does the inner ear arise from
thickening of ectoderm (otic placode) dorsal to PA3 at level of hindbrain and subsequent invagination (otic pit)
what are inner and outer ear malformations often associated with
mandibular defects
