3: Face & Nose Development

Question 1

when do facial primordia appear

Answer 1

week 4

Question 2

where do facial primordia develop

Answer 2

around the stomodeum

Question 3

name the facial primordia

Answer 3

1 frontonasal prominence (rostral to stomodeum)

2 maxillary prominences (lateral to stomodeum)

2 mandibular prominences (caudal to stomodeum)

these are all rostral to the 2nd pharyngeal arch

Question 4

when do most facial structures develop

Answer 4

weeks 4-8

Question 5

facial development in fetal period

Answer 5

cranium expands

eyes shift anteriorly & medially

ears move superiorly

nose is more prominent

proportions become more normal

Question 6

nasal placodes

Answer 6

2 ectodermal thickenings

in frontonasal prominence

end of 4th week

mesenchyme around them form elevations: 2 medial nasal prominences & 2 lateral nasal prominences

Question 7

facial development (months 2-3)

Answer 7

facial features more pronounced

eyes move medially

ears move superiorly (1st ossification centers in skull)

Question 8

nasal pits

Answer 8

week 5 (33 day embryo)

future nostrils (nares)

epithelium of nasal placodes sinks down into underlying mesenchyme to form depressions

sink in due to surrounding elevations (medial & lateral nasal prominences)

Question 9

what forms nasal cavities

Answer 9

both nasal sacs form right & left nasal cavities

Question 10

oronasal membrane

Answer 10

separates nasal cavities from oral cavity

ruptures at end of week 6

Question 11

primordial choanae

Answer 11

help nasal & oral cavities communicate

Question 12

choanae

Answer 12

established from secondary palate

separates nasal cavities from nasopharynx

Question 13

what is olfactory epithelium derived from

Answer 13

neuroectoderm

Question 14

what are nasal conchae derived from

Answer 14

lateral walls of nasal cavity

Question 15

mandibular prominences

Answer 15

fuse at midline first (day 28) before merging with maxillary prominences

Question 16

maxillary prominences

Answer 16

grow in size soon after mandibular prominences fuse

move medially

compress medial nasal prominences in midline

Question 17

medial nasal prominences

Answer 17

compressed by growing maxillary prominences and fuse together

Question 18

nasolacrimal groove

Answer 18

cleft btwn the lateral nasal prominences and the maxillary prominences

lost when lateral nasal prominences fuse with maxillary prominences

Question 19

nasolacrimal duct

Answer 19

ectoderm proliferates into underlying mesenchyme & forms a solid rod that separates from surface & canalizes

superior end=nasolacrimal sac
inferior end=inferior meatus of nasal cavity

Question 20

nasolacrimal sac

Answer 20

dilation of superior end of nasolacrimal duct

Question 21

intermaxillary segment

Answer 21

fused medial nasal prominences

Question 22

labial component of intermaxillary segment

Answer 22

philtrum of upper lip

Question 23

upper jaw component of intermaxillary segment

Answer 23

premaxillary part of maxilla (4 incisors and associated gingiva)

Question 24

palatal component of intermaxillary segment

Answer 24

primary (1*) palate (only the most anterior portion of the hard palate; by incisive foramen/papilla)

Question 25

secondary (2*) palate

Answer 25

remainder of the hard palate & soft palate (and uvula)

Question 26

formation of secondary palate

Answer 26

lateral palatine processes (2 plates of mesenchyme) extend medially from maxillary processes palatine processes project inferomedially, then swing upwards to horizontal position --> fuse with each other, with 1* palate, and with nasal septum

Question 27

incisive foramen

Answer 27

where 2* palate fuses with 1* palate used to indicate ant & post palatal defects

Question 28

median palatine raphe

Answer 28

where lateral palatine processes fuse together

Question 29

hard palate

Answer 29

formed by ossifying the 1* palate and anterior portion of 2* palate

Question 30

soft palate & uvula

Answer 30

posterior-most portion of 2* palate does not ossify

Question 31

cleft lip

Answer 31

anterior palatal defect failure of medial nasal prominences to fuse with maxillary prominences on one or both sides cleft lip=unilateral/bilateral/midline cleft palate=btwn 1* and 2* palates