CFD 6 - face, jaws and mouth 1 Flashcards

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1
Q

What is the fronto-nasal process?

A

prominence in the upper facial area at the most cephalic end of the embryo

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2
Q

What is the ‘cephalic end’?

A

head of a structure such as the trilaminar embryonic disc

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3
Q

What are the mandibular processes?

A

processes of first branchial arch that fuse at the midline to form mandibular arch

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4
Q

What is the mandibular arch?

A

lower dental arch with mandibular teeth or the 1st branchial/pharyngeal arch inferior to the stomodeum in the embryo

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5
Q

What are the maxillary processes?

A

prominence from mandibular arch that grows superiorly and anteriorly on each side of the stomodeum of the embryo

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6
Q

What is the maxillary arch?

A

upper dental arch in which the maxillary teeth form

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7
Q

What is the nasal placode?

A

placodes that develop into olfactory organ for the sensation of smell located in the mature nose

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8
Q

What is a placode?

A

area of ectoderm found in the location of the developing special sense organs on the embryo

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9
Q

When during development is the basic morphology of the face established?

A

between the 4th and 10th week

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10
Q

What develops to establish the basic morphology of the face?

A

the 5 prominences (develop and join together)

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11
Q

What are the 5 prominences in face development?

A
  • frontonasal prominence (overlies the forebrain)
  • 2 maxillary prominences
  • 2 mandibular prominences (associated with the 1st pharyngeal arch)
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12
Q

What does the frontonasal prominence arise from?

A

neural crest cells derived from the mid- and fore-brain

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13
Q

Where are the neural crest cell contributions to the maxillary and mandibular prominences derived from?

A

the mid- and hind-brain

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14
Q

What embryonic layers are involved in facial development?

A

all 3 (endoderm, ectoderm, mesoderm)

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15
Q

What should be happening to the oropharyngeal membrane during the 5th week of development?

A

should see disintegrating oropharyngeal membrane and these prominences growing across

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16
Q

What do the 5 prominences surround?

A

the stomodeum

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17
Q

What is the stomodeum?

A

primitive oral cavity

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18
Q

What separates the stomodeum from the GI tract?

A

an oropharyngeal membrane

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19
Q

What are the 2 types of fusion?

A
  • “fusion” e.g. between medial nasal prominences
  • true fusion e.g. between medial nasal prominence and maxillary process
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20
Q

What happens during “fusion”?

A
  • “fusion” of prominences by elimaintion of furrow
  • proliferation of cells, pushing up of surrounding tissue causing the groove to become more progressively smoother or shallow until it completely smooths out
  • this merging is critical as without it, a deep depression or facial cleft would remain between what used to be the facial processes
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21
Q

What is true fusion?

A
  • true fusion of separate processes
  • two separate processes growing towards each other, touching, and then fusing
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22
Q

What is the primary palate?

A
  • from the fused medial nasal prominences (intermaxillary segment)
  • does not separate oral and nasal cavities - demarcates
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23
Q

What is happening at 26 days of development?

A
  • Placodes forming - rounded areas of thickened ectoderm which will develop into special sense organs
  • Maxillary processes start growing towards eachother
  • Mandibular process undergoing “fusion” - groove becoming more shallow
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24
Q

What is happening at 27 days of development?

A
  • Nasal pits starting to migrate in
  • Maxillary processes starting to enlarge and grow across
  • Mandibular process groove starting to flatten out
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25
Q

What is happening during day 34 of development?

A
  • Growth of the maxillary processes also pulls round the otic placodes which will develop into the eyes
  • Differentiation into medial and lateral nasal prominences
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26
Q

What is happening during day 36 of development?

A
  • Pattern formation
  • Thickenings now starting to differentiate on either side of the foetus
  • These simultaneously start to signal and enlarge
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27
Q

What is happening during the 6th week of development?

A

the ectoderm at the centre of each of the nasal placodes invaginates to form an oval nasal pit

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28
Q

What do the oval nasal pits divide?

A

the frontonasal prominence into the lateral and medial nasal processes

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29
Q

What does the groove between the lateral nasal prominence and the adjacent maxillary prominence form?

A

the naso-lacrimal groove, or the nasal optic furrow

30
Q

What happens to the medial nasal prominences by the end of the 6th week of development?

A

By end of 6th week the medial nasal prominence approximates towards the midline and will then join to form the primordial and the bridge in the septum of the nose

31
Q

What happens to the ectoderm at the floor of the naso-lacrimal groove during the 7th week of development?

A
  • during the 7th week the ectoderm at the floor of this groove invaginates into the underlying mesenchyme to form tubular structures called the naso-lacrimal ducts and sacs
  • the nasal-lacrimal duct is invested in bone during ossification of the maxilla and after birth it functions to drain excess tears from the eye into the nasal cavity
32
Q

What should we have by the end of 6 weeks of development?

A

formation of a basic nose structure but still got a gap between the medial nasal prominence and the maxillary arch

33
Q

What should happen by the end of week 7 of development?

A
  • the inferior tips of the medial nasal process expand laterally and inferiorly to join the intermaxillary process, to form the intermaxillary segment
  • this gives rise to true fusion
  • the intermaxillary process gives rise to the philtrum and then later the primary palate, and it will contain 4 incisor teeth
34
Q

When should the developing face be fairly recognisable as a normal human face?

A

by week 10

35
Q

When is the inter mandibular depression filled, and what by?

A

during week 4 and 5 by proliferating mesenchymal cells

36
Q

When does the oropharyngeal membrane rupture to form a broad slit of the embryonic mouth?

A

during week 5

37
Q

When is the mouth reduced to its final width?

A

weeks 7 and 8, as fusion of the lateral portions of the maxillary and mandibular swellings creates the cheeks

38
Q

What is caused if there is too little fusion when the mouth is being reduced to its final size?

A

macrostomia/large mouth

39
Q

What is caused if there is too much fusion when the mouth is being reduced to its final size?

A

microstomia/small mouth

40
Q

What happens for the mouth to be reduced to its final size?

A

fusion of the lateral portions of the maxillary and mandibular swellings creates the cheeks

41
Q

What part/s of the face does the frontonasal prominence contribute to?

A

forehead, bridge of nose

42
Q

What part/s of the face does the medial nasal prominence contribute to?

A

philtrum of the lip, crest and tip of nose

43
Q

What part/s of the face does the lateral nasal prominence contribute to?

A

alae of nose

44
Q

What part/s of the face does the maxillary prominence contribute to?

A

cheeks, lateral upper lip

45
Q

What part/s of the face does the mandibular prominence contribute to?

A

lower lip

46
Q

What do the streams of mesenchyme into the developing face during week 6 of development do?

A

push back and make sure proliferation goes on, and will form areas such as the secondary palate, septum of the nose etc as they migrate in

47
Q

When during development will we see the first signs of tooth development?

A

week 6

48
Q

What is the first sign of tooth development?

A

primary thickenings of epithelial band, this is where the tooth will start to develop

49
Q

When during development do the palatal shelves start to grow, nasal septum starts to grow down, and tongue is growing?

A

week 7

50
Q

When during development is the oro-nasal cavity being filled up with lots of tissue, the secondary palatal shelves starting to grow down, and the nasal septum starting to migrating and push downwards?

A

as week 7 progresses

51
Q

During week 7, what happens to the mesenchyme of the developing face?

A
  • starting to get condensation of this mesenchyme and differentiation of it - starts to form cartilage
  • mesenchymal cells differentiating into chondroblasts and start to have chondrogenic potential
  • cartilage of nose being formed
52
Q

What will the cartilage formed during week 7 be the primary support for?

A

the developing maxilla and will form the cartilages of the cranial base

53
Q

During developing, when does ossification of the mandible occur?

A

6-7th week

54
Q

During developing, when does ossification of the maxilla occur?

A

8th week

55
Q

During developing, when does ossification of the palate and nasal capsule occur?

A

8th week

56
Q

What are the 2 methods of osteogenesis?

A
  • intramembranous
  • endochondral
    (indistinguishable in mature bone)
57
Q

What is intramembranous ossification?

A
  • the formation of an osteoid within two dense connective tissue sheets, which eventually replaces the connective tissue
  • mesenchymal cells differentiate into osteoblasts from osteoid
58
Q

What are the steps of intramembranous ossification?

A
  • mesenchymal cells —> osteoblasts
  • osteoblasts deposit osteoid…
  • mineral deposited
  • osteoblasts trapped —> osteocytes
59
Q

What is endochondral ossification?

A

cells undergo a different lineage, start to grow round the side of the cartilage and deposit

60
Q

When does the maxilla’s primary centre of intramembranous ossification (for each half of the maxilla) appear?

A

around week 7

61
Q

Where is the maxilla’s primary centre of intramembranous ossification located?

A

at the termination of the infra-orbital nerve, just superior to the dental lamina of the primary maxillary canine tooth in each maxillary process

62
Q

Where are secondary ossification centres for the maxilla found?

A

at the zygomatic, the orbital nasal, nasopalatine, and intermaxillary
- appear and fuse rapidly

63
Q

What do the 2 intermaxillary ossification centres generate?

A

the alveolar ridge, the primary palate region

64
Q

What skeletal subunits can subsequent growth of the maxilla be divided into?

A
  • the basal body unit
  • the nasal unit
  • the alveolar unit
  • the pneumatic unit
65
Q

What does the basal body unit do?

A

develops under the intraorbital nerve and responds to eyeball growth

66
Q

What does the nasal unit depend on?

A

the nasal septal cartilage

67
Q

What does the alveolar unit respond to?

A

tooth growth in the maxilla

68
Q

What does the pneumatic unit reflect?

A

maxillary sinus expansion

69
Q

What molecules/factors have a role in the control of pattern formation?

A
  • retinoic acid
  • five growth factors families implicated in the facial development:
    • BMP, FGF, Shh, Wnt and endothelins

control proliferation, survival and apoptosis

70
Q

What happens if Dlx5 is knocked out?

A

don’t get mandible formation, maxilla is formed in both places