Embryology of Face, Palate and Nasal Cavity Flashcards
pharyngeal apparatus
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where are the ventral facial features derived from?
pharyngeal arch 1 and 2
what ventral facial features are derived from pharyngeal arch 1?
maxilla, mandible, zygomatic and temporal (squamous part) bones
muscles of mastication
what ventral facial features are derived from pharyngeal arch 2?
muscles of facial expression
where do upper and mid-facial structures derive from?
proliferating mesenchyme ventral to developing brain
what 5 swellings are present at week 4 which develop into the face?
frontonasal prominence (with nasal placodes)
2 maxillary prominence (one on each side)
2 mandibular prominences (one on each side)
facial development occurs between which weeks?
4-10
what is the stomedeum?
primitive oral cavity which the 5 swellings at week 4 surround
what forms the nasal placodes?
ectodermal thickenings on the frontonasal prominence
what do the nasal placodes become?
nostrils
what additional swellings arise in week 5 and where do they occur?
2 medial nasal swellings
2 lateral nasal swellings
develop on the frontonasal prominence on the medial and lateral borders of the nasal placodes
the nasal placodes go by another name in week 5, what is this?
nasal pit
facial development in week 6?
slit opens slightly
nasal pit gets deeper
frontonasal prominence gets rounder
medial nasal prominences move towards each other
what happens in week 7?
medial nasal prominences join to form the intermaxillary segment
palate forms
eyes move around to the front of the face
nasolacrimal groove forms (between medial corner of eye to inferior meatus)
what does the nasolacrimal groove become?
nasolacrimal duct
where does the nasolacrimal groove lie between?
maxillary prominence and lateral nasal prominence
what does the nasolacrimal groove do?
solid epithelial cord in floor of groove
cord detaches from the ectoderm
canalization forms the nasolacrimal duct
what are the components of the upper lip?
2 medial nasal prominences
2 maxillary prominences
what forms the lower lip?
mandibular prominences
what are the components of the nose?
frontonasal prominence (bridge and nasal septum)
medial nasal prominences (crest and tip)
lateral nasal prominences (alae (sides))
hoe does the primary palate form and when?
fusion of medial nasal prominences - gives the intermaxillary segment
occurs in week 7
what are the 3 components of the intermaxillary segment and what does each apart form?
labial portion = philtrum of upper lip
upper jaw component = carries 4 incisors
palatal component = forms primary palate
describe palate at 10 weeks?
the primary and secondary palates fuse to create a single hard palate
- point of fusion = incisive foramen
palatal shelves fuse at the median palatine suture
soft palate and uvula extend off the posterior hard palate
what happens to nasal cavities in week 5?
nasal pits deepen and penetrate into the underlying mesenchyme with forward growth of frontonasal prominence
what happens in the nasal cavity in week 6?
as the intermaxillary segment forms, it is connected by a nasal fin
nasal fin vacuolizes and thins, this opens the developing nasal sac
what is the nasal fin called in week 7?
oronasal membrane
what happens in the nasal cavity in week 7?
oronasal membrane disappears allowing the nasal cavities to communicate with oral cavity via primitive choanae
definite choanae open at junction of nasal cavity with pharynx due to formation of secondary palate
primitive vs definitive choanae?
primitive = between oral cavity and nasal cavity definitive = between nasal cavity and nasopharynx
how does the secondary palate form?
right and left palateal shelves develop parallel to the tongue
fused in the central region initially, then expand anteriorly and posteriorly
mandibular development facilitates clearance of the tongue
when does development of the secondary palate occur?
7th - 10th week
why is cleft palate more common in females?
palate development delayed by around 1 week in females
in which gender is cleft lip more common?
males
