Craniofacial Development

Question 1

What are the 5 prominences that contribute to face and jaws? (name specific contributions)

Answer 1

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

Question 2

Stomodeum

Answer 2

• Depression/cavity formed in embryo folding
• Lined w/ ectoderm and internally cont w/ foregut
• Future mouth

Question 3

What do the ectodermal nasal placodes do?

Answer 3

• Invaginate –> nasal pits

- This divides the nasal part of the frontonasal prominence into MEDIAL and LATERAL nasal prominences

Question 4

What forms the upper lip?

Answer 4

2 maxillary prominences and medial nasal prominence (cleft lip if do not fuse fully/properly)

Problems –> cleft LIP

Question 5

Formation of Ears and Neck

Answer 5

1st/2nd branchial arches=external ear, middle ear bones, external auditory meatus

Ectoderm otic placodes = inner ear (SENSORY)

3rd/4th branchial arches = neck

Question 6

What forms the palate? (ant/post)

Answer 6

NEURAL CREST CELLS

Anterior (primary) = medial palatine process fuses w/ lateral palatine shelf

Posterior (secondary) = 2 lateral palatine shelves fuse together

**Problems –> cleft PALATE

Question 7

What germ layers are pouches derived from?

Answer 7

Endoderm and ectoderm

Endoderm = epithelium 
Ectoderm = neural crest cells

Question 8

Which ear bones are derived from branchial arch 1? branchial arch 2?

Answer 8

1- incus and malleus

2- stapes

Question 9

Holoprosencephaly

Answer 9

• 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

Question 10

Fetal Retinoid Syndrome Facial Effects

Answer 10

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

Question 11

Treacher Collins Syndrome

Answer 11

• Hypoplasia of mandible (lower jaw too small)
• Mutations in TCOF1 gene which encodes treacle
• Loss of treacle –> neural crest cell death

Question 12

DiGeorge Syndrome Facial Effects

Answer 12

• 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)

Question 13

What causes induction of the forebrain in development?

Answer 13

Prechordal mesoderm gives of Shh which induces