Palate Development Flashcards

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1
Q

What weeks does formation of the palate occur?

A

weeks 6-12

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2
Q

the development of the palate establishes what?

A

the divide between the nasal cavity and the oral cavity

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3
Q

what fuses together to form the primary palate?

A

The fusion of the medial nasal prominences creates the inter-maxillary segment which forms the primary palate (anterior 1/3rd of the definitive palate)

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4
Q

what is the definitive (secondary) palate important for?

A

mastication - bolus formation
sensation - taste and texture
speech

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5
Q

what gives rise to the palatal shelves?

A

Extomesenchymal cells of the maxillary process migrating in mesially

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6
Q

when do the palatal shelves drop down either side of the tongue?

A

During week 6/7 the palatal shelves grow medially until they bump into the tongue, where they then drop down either side of the tongue (they do not attach to the tongue)

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7
Q

What week do the lateral palatal shelves filp into a horizontal orientation and what does this depend on?

A

Depends of gender
Males - sometimes week 7
Females - usually week 8

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8
Q

What withdraws downwards to allow the lateral palatal shelves to filp?

A

the tongue withdraws down in week 8

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9
Q

What are the extrinsic factor theories as to palatal shelve elevation?

A

Tongue withdrawal due to
- head lifting from cardiac plate
- meckel’s cartilage growth
- increased height of nasal cavity
(true but cause or facilitate elevation)

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10
Q

What are the intrinsic factor theories for palatal shelve elevation?

A
  • hydration of extracellular matrix - hyaluronan (GAG)
  • Mesenchymal cells appear to shorten, contractile microfilaments
  • forces directed via collagen fibres
  • altered blood flow
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11
Q

By the end of week 8, what is happening?

A

Towards the end of week 8 we have mesenchyme migrating in, matrix being laid down and epithelial proliferation around the outside
we start to get the beginning of the shelves touching
By the end of week 8 the lateral shelves have grown across the midline and they’re starting to form a secondary palate

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12
Q

The palatal shelves fuse in what direction?

A

fuse from the front first towards the back

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13
Q

How long does it take for the palatal shelves to fully fuse?

A

about 4 weeks

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14
Q

What week do we have a fully fused palate (primary palate down the secondary shelves right to the back of the mouth)?

A

week 12

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15
Q

What are the 2 types of fusion in development?

A

Non true fusion - removal of a gap from pushing up from a furrow
True fusion - two differenet things fusing together and forming a midline

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16
Q

What type of fusion in palate development

A

true fusion

17
Q

Once the two palatal shelves have come together and actually touched, what is the group of cells down the middle called?

A

midline epithelial cells

18
Q

Why does the epithelial of the palatal shelves not fuse with the tongue when they bump into each other, but will fuse with each other?

A

The epithelial cells produce very specific glycoproteins (sticky surface), the ones on the palatal shelve surfaces are different to the ones on the tongue so will not fuse

19
Q

What are the 3 theories for mid-line epithelial cell disintegration?

A

1 Epithelial-mesenchymal transition
2 Apoptosis of epithelial cells
3 Migration to the nasal or oral edge

20
Q

What causes epithelial cell rests?

A

some of the midline epithelial cells do not migrate/apoptosis or transition into mesenchyme which result in cell rests

21
Q

What is the problem with epithelial cell rests

A

Epithelial cells rests have cystic potential which can cause pain in the roof of the mouth

22
Q

What is it called if the palate fails to fuse (either completely or partially)

A

Cleft palate

23
Q

What is a teratogen?

A

a substance that interferes with normal fetal development and causes congenital disabilities

23
Q

What are the risk factor for palatal clefts?

A

Smoking
alcohol abuse
Drugs - both medical and recreational
viruses
rubella
Too much vitamin A (or other retinoids
Deficiencies in folic acid

23
Q

Are cleft palates more common in males or females?

A

Females (thought maybe because the fusion process starts later?)

23
Q

What 3 enzymes synthises HA (Hyaluronic acid)?

A

HA synthase 1
HA synthase 2
HA synthase 3

24
Q

What is synthesised by HA synthase 1, HA synthase 2 and HA synthase 3 and found of different chromosomes and expressed different times during development?

A

HA (hyaluronic acid/hyaluronan)

25
Q

What two enzymes produce large molecular weight of HA?

A

HA synthase 1 and 2

26
Q

What enzyme produces a smaller molecular weight of HA?

A

HA synthase 3

27
Q

What HA synthase do you get mainly during early development

A

HA synthase 2

28
Q

What is a knock out mouse?

A

a laboratory mouse in which one or more genes have been turned off or “knocked out. This is to silence the gene of interest

29
Q

In what knock out mice do you get a cleft palate? What gene is turned off?

A

TGF beta 3

30
Q
A