Palate Development

Question 1

What weeks does formation of the palate occur?

Answer 1

weeks 6-12

Question 2

the development of the palate establishes what?

Answer 2

the divide between the nasal cavity and the oral cavity

Question 3

what fuses together to form the primary palate?

Answer 3

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

Question 4

what is the definitive (secondary) palate important for?

Answer 4

mastication - bolus formation
sensation - taste and texture
speech

Question 5

what gives rise to the palatal shelves?

Answer 5

Extomesenchymal cells of the maxillary process migrating in mesially

Question 6

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

Answer 6

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)

Question 7

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

Answer 7

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

Question 8

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

Answer 8

the tongue withdraws down in week 8

Question 9

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

Answer 9

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

Question 10

What are the intrinsic factor theories for palatal shelve elevation?

Answer 10

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

Question 11

By the end of week 8, what is happening?

Answer 11

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

Question 12

The palatal shelves fuse in what direction?

Answer 12

fuse from the front first towards the back

Question 13

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

Answer 13

about 4 weeks

Question 14

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

Answer 14

week 12

Question 15

What are the 2 types of fusion in development?

Answer 15

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

Question 16

What type of fusion in palate development

Answer 16

true fusion

Question 17

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

Answer 17

midline epithelial cells

Question 18

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?

Answer 18

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

Question 19

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

Answer 19

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

Question 20

What causes epithelial cell rests?

Answer 20

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

Question 21

What is the problem with epithelial cell rests

Answer 21

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

Question 22

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

Answer 22

Cleft palate

Question 23

What is a teratogen?

Answer 23

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

Question 23

What are the risk factor for palatal clefts?

Answer 23

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

Question 23

Are cleft palates more common in males or females?

Answer 23

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

Question 23

What 3 enzymes synthises HA (Hyaluronic acid)?

Answer 23

HA synthase 1
HA synthase 2
HA synthase 3

Question 24

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?

Answer 24

HA (hyaluronic acid/hyaluronan)

Question 25

What two enzymes produce large molecular weight of HA?

Answer 25

HA synthase 1 and 2

Question 26

What enzyme produces a smaller molecular weight of HA?

Answer 26

HA synthase 3

Question 27

What HA synthase do you get mainly during early development

Answer 27

HA synthase 2

Question 28

What is a knock out mouse?

Answer 28

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

Question 29

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

Answer 29

TGF beta 3