3: Face & Nose Development Flashcards
when do facial primordia appear
week 4
where do facial primordia develop
around the stomodeum
name the facial primordia
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
when do most facial structures develop
weeks 4-8
facial development in fetal period
cranium expands
eyes shift anteriorly & medially
ears move superiorly
nose is more prominent
proportions become more normal
nasal placodes
2 ectodermal thickenings
in frontonasal prominence
end of 4th week
mesenchyme around them form elevations: 2 medial nasal prominences & 2 lateral nasal prominences
facial development (months 2-3)
facial features more pronounced
eyes move medially
ears move superiorly (1st ossification centers in skull)
nasal pits
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)
what forms nasal cavities
both nasal sacs form right & left nasal cavities
oronasal membrane
separates nasal cavities from oral cavity
ruptures at end of week 6
primordial choanae
help nasal & oral cavities communicate
choanae
established from secondary palate
separates nasal cavities from nasopharynx
what is olfactory epithelium derived from
neuroectoderm
what are nasal conchae derived from
lateral walls of nasal cavity
mandibular prominences
fuse at midline first (day 28) before merging with maxillary prominences
maxillary prominences
grow in size soon after mandibular prominences fuse
move medially
compress medial nasal prominences in midline
medial nasal prominences
compressed by growing maxillary prominences and fuse together
nasolacrimal groove
cleft btwn the lateral nasal prominences and the maxillary prominences
lost when lateral nasal prominences fuse with maxillary prominences
nasolacrimal duct
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
nasolacrimal sac
dilation of superior end of nasolacrimal duct
intermaxillary segment
fused medial nasal prominences
labial component of intermaxillary segment
philtrum of upper lip
upper jaw component of intermaxillary segment
premaxillary part of maxilla (4 incisors and associated gingiva)
palatal component of intermaxillary segment
primary (1*) palate (only the most anterior portion of the hard palate; by incisive foramen/papilla)
secondary (2*) palate
remainder of the hard palate & soft palate (and uvula)
formation of secondary palate
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
incisive foramen
where 2* palate fuses with 1* palate
used to indicate ant & post palatal defects
median palatine raphe
where lateral palatine processes fuse together
hard palate
formed by ossifying the 1* palate and anterior portion of 2* palate
soft palate & uvula
posterior-most portion of 2* palate
does not ossify
cleft lip
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
