3.2.2 Embryology of Facial Development

Question 1

What are the epidemiological characteristics of human cleft lip and palate?

Answer 1

Question 2

What is the role of neural crest cells?

Answer 2

Question 3

First arch syndromes are described as?

Answer 3

Congenital malformations that result from mutations in genes that play a role in neural crest function (induction, proliferation, migration)

Question 4

What are the characteristics of Di-Georges Syndrome?

Answer 4

CATCH-22 - Cardiac abnormality (outflow tract abnormalities), Abnormal facies, Thymic aplasia (T Cell Deficiency), Cleft palate, Hypocalcemia/Hypoparathyroidism, deletion on chromosome 22

Neural crest cells migrate into the ultimobranchial body which forms from the ventral part of the 4th pouch or the 5th pouch (if it forms in humans). The C cells of the thyroid are therefore derived from neural crest cells. Please note the vertical transposition of the parathyroids developing from the 3rd and 4th pouches.

Question 5

What are the characteristics of Treacher-Collins Syndrome?

Answer 5

underdevelopment of zygomatic bones and mandible, malformed ears, down-slanting eye lids

Question 6

What are the characteristics of Pierre-Robin Sequence?

Answer 6

mostly mandibular hypoplasia, cleft palate, posterior tongue

Question 7

What are the characteristics of holoprosencephaly?

Answer 7

Question 8

What are the characteristics of FAS?

Answer 8

Question 9

Answer the question, but also explain why the other answers are wrong?

Answer 9

Question 10

What are the covered parts?

Answer 10

Question 11

What is the function of the frontonasal prominence?

Answer 11

grows down and around nasal pits → forehead, nose bridge

Question 12

What is the function of the medial nasal prominence?

Answer 12

fuse to form the philtrum, dorsum and tip of nose

Question 13

What is the role of the lateral nasal prom?

Answer 13

ala of the nose (nostrils)

Question 14

What is the role of the Nasal lacrimal duct ?

Answer 14

ectodermal groove → connects lacrimal sac with inferior meatus of nasal cavity

Question 15

What is the role of the maxillary prominence?

Answer 15

2, grow toward the midline → cheeks and lateral upper lip

Question 16

What is the role of the mandibular prominence?

Answer 16

2, fuse in the midline → jaw

Question 17

Answer the question, but also explain why the others are wrong.

Answer 17

Question 18

Describe the formation of the nasal cavities?

Answer 18

oronasal membrane breaks down to form continuous cavity with mouth

Question 19

What is the difference between the primary and secondary palate?

Answer 19

Primary – small separation between nasal and oral cavities → premaxilla and upper lip

Secondary – forms to again separate nasal and oral cavities

Question 20

What is the relationship between the palatine shelves and the tongue?

Answer 20

Question 21

What is the difference between the intermaxillary segment and the maxillary process?

Answer 21

inter - – aka globular processes fuse

Maxillary process – palatine shelves fuse in the midline (hard palate) to close the roof of the oral cavity

Question 22

What is the answer and explain why the others are wrong.

Answer 22

Question 23

What is the cause of clefts?

Answer 23

persistent labial groove or late fusion with expanding head

Question 24

What is the cause of a cleft lip?

Answer 24

Failure of fusion of the maxillary and medial nasal processes (formation of primary palate)

Question 25

What are the causes of a cleft palate?

Answer 25

Failure of fusion of the two lateral palatine shelves or failure of fusion of lateral palatine shelves with the nasal septum and/or median palatine shelf (formation of secondary plate)