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E: Human Morphogenesis and Embryologically > Neurulation > Flashcards

Neurulation Flashcards

1
Q

Neurulation?

A

Process whereby the neural plate forms the neural tube

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2
Q

End of week 3 what happens?

A

The lateral edges of the neural plate become elevated to form neural folds.

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3
Q

Day 19-20?

A

Depressed midregion forms the neural groove

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4
Q

Day 22-23?

A

The neural folds approach each other in the midline.

They fuse

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5
Q

Where does the fusion begin?

A

At the cervical region (5th somite)

Proceeds cranially and caudally.

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6
Q

Name the 5 stages of neurulation?

A
  1. Shaping
  2. Folding
  3. Elevation
  4. Converence
  5. Closure

AS67

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7
Q

Shaping?

A

Cells elongate and neural plate thickens

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8
Q

Folding?

A

Local cell shape changes around the MHP

Cells anchor to the notochord and change their shape.

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9
Q

How thick was the neural plate before shaping?

A

1 cell thick

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10
Q

Elevation?

A

Involves cell shorten at apical side (Facing the lumen)

Microfilaments appear in cells and are required for apical constriction- facilitates the bending of the tissue

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11
Q

Closure?

A

Dorsal-lateral hinge point-

-Become wedge-shape and promote final closure

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12
Q

Closure of the cranial neuropore occurs at?

A

Day 25

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13
Q

Posterior neuropore closes at day?

A

Day 28

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14
Q

Secondary Neurulation?

A

Remaining neural tube is formed by this process.

More prominent in animals with large tails.

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15
Q

Difference in the lumen formation between primary and secondary neurulation?

A

AS68

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16
Q

What does the secondary neurulation appear to form with?

A

Form with the formation of condensation of mesenchymal cells beneath the dorsal ectoderm of the tail bud.

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17
Q

Caviatation?

A

Formation of a space within a mass of cells.

Secondary neurluation mesenchymal rod forms a central canal

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18
Q

How is the secondary and primary neurulation join up?

A

Joins up once the mesenchymal rod undergoes caviation and then can it be contrinou with the primary neurulation

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19
Q

When is the medullary cord formed in secondary neurulation?

A

Day 20

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20
Q

What day is secondary neurulation complete?

A

Day 40

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21
Q

How is secondary neurulation formed?

A

AS69

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22
Q

Why is secondary neurulation important?

A

In caudal regions, a tail bud forms and caudal most neural tube is formed by secondary neurulation

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23
Q

Primary neurulation involves?

A

Rolling up of a flat neuroepithelium/ neural plate to form a tube.

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24
Q

Secondary neurulation involves?

A

Caviation of a central core of mesenchymal cells which epithelialise to form a neural tube

25
Q

What does the primary neurulation account for?

A

The formation of most of the CNS

26
Q

Secondary neurulation accounts for?

A

Only the caudal most region.

lumbosacral neurous system

27
Q

How many neural closures do mice have?

Name them all

AS70

A

3.

  1. Where somites form
  2. Beginning at the midbrain
  3. Forebrain
28
Q

How many neural closures do humans have?

Name them and the differences to mice?

AS70

A

2 closures

Closure 1 is longer in humans

  1. Closure 1
  2. Closure 3
29
Q

How many pregnancies are affected by neural tube defects?

A

0.5-2 per 1000.

30
Q

Anencephaly?

A

The neural tube fails to close in the cranial form

31
Q

Spina bifida?

A

Closure fails anywhere caudually from the cervical region

32
Q

Exencephaly develops into?

A

Anencephaly

Due to the tissue being in the wrong place and therefore coming into contact with cellular processes

33
Q

Exencephaly?

A

No scythe gene

This gene controls programmed cell death

Therefore over-proliferation and no differentiation

34
Q

Anencephaly?

A

Occurs when neural folds fail to fuse and neural tissue fails to differentiate.

35
Q

Spina bifida?

A

Failure to close the vertebrate canal.

36
Q

Spinal bifida occulta?

A

Mild

The neural tube is intact but the vertebrate does not completely fuse

37
Q

Meningomyelocele?

A

Severe form of spina bifida

Neural tube bulges out into a cyst- neural tube now expose to an environemnt it isnt suppose to be exposed to.

38
Q

Sex difference for exencephaly and anencephaly?

A

Ratio

1:3

Male: female

Due to the double X and not the lost of males during pregnancy

39
Q

Sex difference for spinal bifida?

A

Equal between males and females

40
Q

What determines an individuals risk of malformation?

A

Multi-factorial with genes and environment

41
Q

How many genes cause NTD in mice?

A

Over 200 genes

42
Q

PCP genes of the signalling pathway?

A

Many be a cause of NTD in some cases

43
Q

Other signal that could cause NTD?

A

Shh

Causes neural fold bending

44
Q

Disruption in the PCP pathway?

A

Results in a wide neural plate.

Prevents the neural folds from contacting each other

45
Q

Craniorachischsis?

A

The neural plate remains open from the brain to the spinal cord.

Most severe type of NTDs

46
Q

Wnt5a?

A

Regulates the polarity of the cell

47
Q

Vang1/2 mutation?

A

Neural plate remains wide

48
Q

How does loss of Shh generate NTDs?

A

Embryos lack ventral midline structures.

Not critical for mechanical closure of the neural plate.

Both alleles have to be mutated.

49
Q

Over-active Shh?

A

Neural tissue becomes ventralised

Without dorsal region it fails to close

Open spinal cord and brain

Reduced MHP and DLHP expression

50
Q

Shh signalling regulates

A

promotes proliferation

regulates apoptosis

Inhibits the formation of the DLHP

51
Q

Name the 4 environmental factors contributing to NTDs?

A
  1. Diabetes
  2. Hyperthermia
  3. Obesity
  4. Micro-nutrient deficiencies
52
Q

Diabetes?

A

Maternal hyperglycemia

Altered glucose levels

53
Q

Hyperthermia

A

Maternal fever in weeks 3-4 of pregnancy

54
Q

Obesity?

A

Maternal metabolic disturbances affecting glucose, insulin and other factors

55
Q

Micro-nutirent deficiencies?

Name the 4?

A

Zinc

Ionitol: distube in PKC downstream.

Folate: Disturbances in folate-related metabolism

Vitamin B12: Disturbances in folate-related metabolism.

56
Q

What can you take to prevent nerual tube defects?

A

Prevented by taking folic acid around conception

57
Q

Folic acid synthesis?

A

Involve effects on the methylation cycle

Regulates gene expression and protein activity

58
Q

How was folic acid introduced to the whole population?

A

Introduced in flour

E: Human Morphogenesis and Embryologically (15 decks)

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