Maxillofacial Embryology

Question 1

how many prominences develop on the human face

Answer 1

5

Question 2

what are terms interchangeable with prominences

Answer 2

swelling or process

Question 3

what do facial prominences predominantly consist of

Answer 3

*neural crest derived mesenchyme from first pharyngeal arches

Question 4

what happens at week 4 in relation to the prominences

Answer 4

5 prominences surrounds the stomodeum

Question 5

what and where are prominences 1&2

Answer 5

maxillary prominences, lateral to the stomodeum

Question 6

what and where are prominences 3&4

Answer 6

mandibular prominences, caudal to the stomodeum

Question 7

what and where is prominence 5

Answer 7

frontonasal prominence, rostral to the stomodeum

Question 8

where are the nasal (olfactory) placodes*

Answer 8

on both sides of the frontonasal prominence, thickenings of surface ectoderm

Question 9

what is the stomodeum*

Answer 9

precursor to the mouth

Question 10

what occurs during week 5

Answer 10

• *nasal placodes invaginate from nasal pits
• *nasal prominences

Question 11

what forms on the nasal pits during week 5

Answer 11

• a new ridge of tissue forms on each side of the pits
• this forms the *medial nasal prominence and *lateral nasal prominence

Question 12

what happens for weeks 6-10 for the lips

Answer 12

*maxillary prominences increase in size and grow medially compressing the *medial nasal prominences toward the midline
*the lower lip& mandible are formed

Question 13

what occurs during weeks 6-10 to the maxillary and medial nasal prominences? what does this form?

Answer 13

• 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

Question 14

what is the nasolacrimal groove*

Answer 14

deep furrow separating maxillary and lateral nasal prominences

Question 15

what is the nasolacrimal duct*

Answer 15

ectoderm forms a canal at the base of the groove

Question 16

what forms the nasolacrimal sac

Answer 16

upper end of the duct forms this structure

Question 17

what occurs once the duct of the nasolacrimal sac forms

Answer 17

*maxillary and lateral nasal prominences merge (supposed to)

Question 18

where is the duct near the nasolacrimal sac located

Answer 18

duct runs from the *medial corner of the eye to the *inferior meatus of the nasal cavity

Question 19

what happens to the maxillary prominences during week 6-10

Answer 19

*they enlarge to form the cheeks and maxillae

Question 20

what is the nose formed by during weeks 6-10*

Answer 20

formed from 5 facial prominences

Question 21

what are the 5 facial prominences that form the nose

Answer 21

1) *frontonasal prominence forms the bride
2&3) *merged medial prominences form the crest and tip
4&5) lateral nasal prominences form the alae

Question 22

by week 7 what has merged? what structure has been created?

Answer 22

-merging of the maxillary prominences and medial nasal prominences
- creates the *INTERMAXILLARY SEGMENT
- secondary palate begins to fuse

Question 23

what are the 3 components of the intermaxillary segment

Answer 23

1) * labial component = philtrum of the upper lip
2) * upper jaw component = four incisor teeth
3) * palatal component= triangular *primary palate

Question 24

what is the I.S. continuous with?

Answer 24

w/ the rostral portion of the *nasal septum which is formed by the frontal prominence

Question 25

how do the primary and secondary palates compare?

Answer 25

- primary palate is relatively small compared to secondary - secondary becomes the main part of the definitive palate

Question 26

what forms the secondary palate

Answer 26

two shelf-like outgrowths from the maxillary prominences called the *palatine shelves

Question 27

how does fusion of the palatal shelves take place*

Answer 27

- 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

Question 28

what is the incisive foramen*

Answer 28

midline landmark between the primary and secondary plates

Question 29

what 5 changes occur to the nasal cavity during weeks 6-9

Answer 29

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

Question 30

what is the oronasal membrane

Answer 30

- 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

Question 31

where are definitive choanae

Answer 31

lie at the junction of the nasal cavity and pharynx

Question 32

how do paranasal air sinuses develop

Answer 32

as diverticula of the lateral nasal wall and extend into the maxilla, ethmoid, frontal, and sphenoid bones, reaching definitive size at puberty

Question 33

what are 4 leading reasons why structures don't fuse

Answer 33

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

Question 34

what is the most common syndrome associated with clefting*

Answer 34

van der woude syndrome - cleft lip w/ or w/o cleft palate - paramedian lip pits

Question 35

what is pierre robin sequence

Answer 35

- cleft palate, one of the syndromes where structures don't fuse - mandibular micrognathia - glossoptosis

Question 36

what is treacher collins syndrome? the alternate name?

Answer 36

- 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

Question 37

what is the origination of cleft lip

Answer 37

defective fusion of the *medial nasal process with the *maxillary process

Question 38

what is the origination of cleft palate

Answer 38

failure of the *palatal shelves to fuse (secondary palate)

Question 39

what demographic has cleft palate only

Answer 39

30% of people affected have CPO - female predominance*

Question 40

what demographic has CL+/-CP

Answer 40

70% overall -male predominance*

Question 41

how does race play into cleft palate

Answer 41

NA 2x more than Asians Asians 1.5x more than white white 2x more than black

Question 42

where is an oblique facial cleft? what is it?

Answer 42

- along the nasolacrimal groove - failure of the *maxillary prominence* to merge with the *lateral nasal prominence*

Question 43

what is median cleft lip

Answer 43

- failure of the medial nasal prominences to merge - holoprosencephaly: spectrum w/ most severe being loss of midline structure & fusion of lateral ventricles of brain

Question 44

what are important features of commissural lip pits

Answer 44

- 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

Question 45

what are important features of paramedian lip pits

Answer 45

- 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)

Question 46

what is double lip

Answer 46

- congenital- approx., 3rd month of gestation - acquired- ascher syndrome

Question 47

what are important features of palatal cysts of the newborn

Answer 47

-trapped islands of epithelium when palatal shelves fuse - epstein perals, bohn nodules