Maxillofacial Embryology Flashcards
how many prominences develop on the human face
5
what are terms interchangeable with prominences
swelling or process
what do facial prominences predominantly consist of
*neural crest derived mesenchyme from first pharyngeal arches
what happens at week 4 in relation to the prominences
5 prominences surrounds the stomodeum
what and where are prominences 1&2
maxillary prominences, lateral to the stomodeum
what and where are prominences 3&4
mandibular prominences, caudal to the stomodeum
what and where is prominence 5
frontonasal prominence, rostral to the stomodeum
where are the nasal (olfactory) placodes*
on both sides of the frontonasal prominence, thickenings of surface ectoderm
what is the stomodeum*
precursor to the mouth
what occurs during week 5
- *nasal placodes invaginate from nasal pits
- *nasal prominences
what forms on the nasal pits during week 5
- a new ridge of tissue forms on each side of the pits
- this forms the *medial nasal prominence and *lateral nasal prominence
what happens for weeks 6-10 for the lips
*maxillary prominences increase in size and grow medially compressing the *medial nasal prominences toward the midline
*the lower lip& mandible are formed
what occurs during weeks 6-10 to the maxillary and medial nasal prominences? what does this form?
- clef between the *medial nasal prominence and maxillary prominence should be LOST and 2 structures fuse
- *upper lip is formed by *2 medial nasal prominences and *2 maxillary prominences
what is the nasolacrimal groove*
deep furrow separating maxillary and lateral nasal prominences
what is the nasolacrimal duct*
ectoderm forms a canal at the base of the groove
what forms the nasolacrimal sac
upper end of the duct forms this structure
what occurs once the duct of the nasolacrimal sac forms
*maxillary and lateral nasal prominences merge (supposed to)
where is the duct near the nasolacrimal sac located
duct runs from the *medial corner of the eye to the *inferior meatus of the nasal cavity
what happens to the maxillary prominences during week 6-10
*they enlarge to form the cheeks and maxillae
what is the nose formed by during weeks 6-10*
formed from 5 facial prominences
what are the 5 facial prominences that form the nose
1) *frontonasal prominence forms the bride
2&3) *merged medial prominences form the crest and tip
4&5) lateral nasal prominences form the alae
by week 7 what has merged? what structure has been created?
-merging of the maxillary prominences and medial nasal prominences
- creates the *INTERMAXILLARY SEGMENT
- secondary palate begins to fuse
what are the 3 components of the intermaxillary segment
1) * labial component = philtrum of the upper lip
2) * upper jaw component = four incisor teeth
3) * palatal component= triangular *primary palate
what is the I.S. continuous with?
w/ the rostral portion of the *nasal septum which is formed by the frontal prominence
how do the primary and secondary palates compare?
- primary palate is relatively small compared to secondary
- secondary becomes the main part of the definitive palate
what forms the secondary palate
two shelf-like outgrowths from the maxillary prominences called the *palatine shelves
how does fusion of the palatal shelves take place*
- begins in the anterior palate and progresses posteriorly
- also ascend to horizontal position above the tongue and fuse
- nasal septum grows down and joins the newly formed palate
what is the incisive foramen*
midline landmark between the primary and secondary plates
what 5 changes occur to the nasal cavity during weeks 6-9
1) nasal pits deepen
2) growth of surrounding tissue
3) penetration into the underlying mesenchyme
4) oronasal membrane
5) definitive choanae once palate forms and nasal chambers develop
what is the oronasal membrane
- separates the pits from the primitive oral cavity via the foramina named *primitive choanae
- lie on each side of the midline immediately behind the primary palate
where are definitive choanae
lie at the junction of the nasal cavity and pharynx
how do paranasal air sinuses develop
as diverticula of the lateral nasal wall and extend into the maxilla, ethmoid, frontal, and sphenoid bones, reaching definitive size at puberty
what are 4 leading reasons why structures don’t fuse
1) maternal use of valproic acid (anticonvulsant med)
- 10x greater frequency of clefting
2) maternal smoking
- doubles the frequency of clefting
3) maternal alcohol
4) syndromic
what is the most common syndrome associated with clefting*
van der woude syndrome
- cleft lip w/ or w/o cleft palate
- paramedian lip pits
what is pierre robin sequence
- cleft palate, one of the syndromes where structures don’t fuse
- mandibular micrognathia
- glossoptosis
what is treacher collins syndrome? the alternate name?
- one of the syndromes where structures don’t fuse
- 1st and 2nd branchial arch defects
-> cleft palate, narrow cheeks, underdeveloped mandible, lateral facial clefting - mandibulofacial dysostosis
what is the origination of cleft lip
defective fusion of the *medial nasal process with the *maxillary process
what is the origination of cleft palate
failure of the *palatal shelves to fuse (secondary palate)
what demographic has cleft palate only
30% of people affected have CPO
- female predominance*
what demographic has CL+/-CP
70% overall
-male predominance*
how does race play into cleft palate
NA 2x more than Asians
Asians 1.5x more than white
white 2x more than black
where is an oblique facial cleft? what is it?
- along the nasolacrimal groove
- failure of the maxillary prominence to merge with the lateral nasal prominence
what is median cleft lip
- failure of the medial nasal prominences to merge
- holoprosencephaly: spectrum w/ most severe being loss of midline structure & fusion of lateral ventricles of brain
what are important features of commissural lip pits
- failure of normal fusion of the maxillary and mandibular processes
- NOT associated with facial or palatal clefts
- corners of mouth, can develop later in life
what are important features of paramedian lip pits
- rare congenital invaginations of lower lip from persistent lateral sulci on embryonic mandibular arch, usually disappear by week 6
- usually inherited as an autosomal dominant trait (e.g. van der woude syndrome)
what is double lip
- congenital- approx., 3rd month of gestation
- acquired- ascher syndrome
what are important features of palatal cysts of the newborn
-trapped islands of epithelium when palatal shelves fuse
- epstein perals, bohn nodules
