Lecture #49 - formation of the primary germ cells layers

Question 1

In the early embryo (like morula), the cells are t_____ = what does this mean?

Answer 1

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Question 2

By day 5 after fertilisation, what two types of cells? Are these totipotent? What’s their term? What does this have to do with embryonic stem cells?

Answer 2

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Question 3

After the blastocyst forms the trophoblast and the inner cell mass - what happens to the inner cell mass?

What cells move around to form amniotic membrane vs yolk sac?

Answer 3

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Question 4

1. What is the definition of gastrulation?
2. So the cells in each layer have a define ______ and they are no longer ____ cells - so cells are ‘s_____’
3. What 4 things does development of the germ layers involve?
4. What is the meaning of differentiation?

Answer 4

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Question 5

At the end of the 2nd week. the primitive streaks forms WHERE?

Answer 5

epiblast or future ectoderm

Question 6

What is the primitive streak? (pink definition slide 14)

The side with the pink streak - will it be anterior or posterior end of the embryo?

Answer 6

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Question 7

1. Cells migrate down into the primitive streak to form both _____ and ______ - how?
2. Cells are moving from where?

Answer 7

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Question 8

In your head, draw out slide 16

Answer 8

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Question 9

Cells of he epiblast move towards the primitive streak and migrate downwards pushing…….and forming………

Answer 9

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Question 10

Summary: what were the cells in the bilaminar embryonic disc and what in the trilaminar disc?

Answer 10

Epiblast + Hypoblast vs ectoderm, mesoderm and endoderm

Question 11

Js but yeah, the primitive streak “forms in the epiblast/future ectoderm” (slide 13) but it is an ‘invagination between both layers of bilaminar cells resulting in 3 layers so cells grow towards primitive stream and slip under epiblast”

Answer 11

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Question 12

Germ cell layers (slide 23):

1. Embryonic folding = what is it?
2. What’s inside and what’s middle and outside?

Answer 12

1. Embryonic folding = go from a flat disc to tube (folded embryo)

Question 13

Ectoderm - what 5 things does it form?

Answer 13

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Question 14

What do the three layers do so the ectoderm can form the skin?

Answer 14

Basically, the yolk sac pinches off and there is the formation of the gut tube (inside is endoderm) and the amniotic cavity surrounds the embryo and there is the ectoderm around the outside of the embryo

Question 15

1. What is neurulation?
2. What are the three stages>
3. What are two conditions that can occur if neurulation goes wrong?

Answer 15

3. So the neural tube parts close at different times. The middle closes first and then the anterior and then the posterior.
   The anterior closes to form the brain and the posterior region of neural tube form the spinal cord. Because these parts close at different times, can have anacephaly or spina bifida.
   Anacephaly is where failure of brain to form and the end remains open - forms neural tissue just an open flat disc so won’t develop.
   Spina bifida is where posterior fails to close and you get (depending on how much it didn’t close) there can be a big cyst that forms with parts of spinal cord coming out and into cyst. Vertebrae don’t form properly if neural tube open

Question 16

1. Mesoderm - what 4 things does it form?
2. Mesoderm can be split up into diff regions depending on where the cells end up in the layer - what are the three types of mesoderms?
3. What two things does the intermediate mesoderm form?
4. What 5 things does the paraxial mesoderm form?
5. What two things does the lateral mesoderm form?

Answer 16

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Question 17

Endoderm - what two things listed that it forms/lines?

Answer 17

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Question 18

Sometimes the germ cell layers don’t form so what can this result in?

Answer 18

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Question 19

What do you get if insufficient mesoderm in lower part of the body?

Answer 19

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