Craniofacial Development Flashcards
What are the 5 prominences that contribute to face and jaws? (name specific contributions)
Frontonasal prominence (forehead/nasal region)
2 maxillary prominences (upper lip) and 2 mandibular prominences (jaw, floor of mouth, part of tongue)
Both from branchial arch 1
Stomodeum
- Depression/cavity formed in embryo folding
- Lined w/ ectoderm and internally cont w/ foregut
- Future mouth
What do the ectodermal nasal placodes do?
- Invaginate –> nasal pits
- This divides the nasal part of the frontonasal prominence into MEDIAL and LATERAL nasal prominences
What forms the upper lip?
2 maxillary prominences and medial nasal prominence (cleft lip if do not fuse fully/properly)
Problems –> cleft LIP
Formation of Ears and Neck
1st/2nd branchial arches=external ear, middle ear bones, external auditory meatus
Ectoderm otic placodes = inner ear (SENSORY)
3rd/4th branchial arches = neck
What forms the palate? (ant/post)
NEURAL CREST CELLS
Anterior (primary) = medial palatine process fuses w/ lateral palatine shelf
Posterior (secondary) = 2 lateral palatine shelves fuse together
**Problems –> cleft PALATE
What germ layers are pouches derived from?
Endoderm and ectoderm
Endoderm = epithelium Ectoderm = neural crest cells
Which ear bones are derived from branchial arch 1? branchial arch 2?
1- incus and malleus
2- stapes
Holoprosencephaly
- Midface reduction in midline tissues
- May be die to dec in Shh which is responsible for forebrain induction (so no induction means dec midline structures)
- Shh also regulates crest development which would affect facial bones/cart/connective tissue
Fetal Retinoid Syndrome Facial Effects
RA regulates Hox patterning in hindbrain and branchial arches
RA also regulates Shh (also messes w/ later facial development)
So this disorder (inc RA) –> mispatterning of hindbrain and crests –> underdevelopment of face, CNS probs, palate defects
Treacher Collins Syndrome
- Hypoplasia of mandible (lower jaw too small)
- Mutations in TCOF1 gene which encodes treacle
- Loss of treacle –> neural crest cell death
DiGeorge Syndrome Facial Effects
- Tbx1 mutation
- Tbx1 normally influences migration of neural crest cells in branchial arches AND pouches 3 and 4
- No Tbx1 –> underdevelopment of pouches 3/4 –> parathyroid/thyroid and thymus under develop –> infections (thymus) and abnormal calcium regulation leading to seizures (parathyroid/thyroid)
What causes induction of the forebrain in development?
Prechordal mesoderm gives of Shh which induces
