Implantation and formation of germ layers Flashcards

1
Q

What happens when the blastocyst adheres to the endometrium

A

Implantation begins

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2
Q

Where does implantation occur

A

On the posterior wall of the uterus and nearer the fundus (top bit) than the cervix

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3
Q

what happens to the zone pellucida in implantation

A

Disappearance of it

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4
Q

What happens to the blastocyst in implantation

A

Gives rise to inner cell mass and trophoblast

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5
Q

What happens in the uterine lining in implantation

A

a ‘decimal reaction’ whereby there is increased secretory function

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6
Q

What does the inner cell mass form

A

The embryo and some membranes

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7
Q

What color is the primitive ectoderm

A

Blue

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8
Q

What color is the primitive endoderm

A

Yellow

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9
Q

What does the inner cell mass give rise to

A

primitive ectoderm

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10
Q

What dos the ectoderm surround

A

Amniotic cavity

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11
Q

What does the endoderm surround

A

Cavity of the yolk sac

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12
Q

How many layers does the blastocyst wall have

A

2

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13
Q

What the trophoblast form

A

extraembryonic embryonic mesoderm

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14
Q

What is the extra embryonic mesoderm

A

The red cells between the inner cell mass and the trophoblast (green bit)

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15
Q

What is the decimal reaction

A

Endometrium undergoes it

-GLycogen/lipid distended cells and glands swell more

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16
Q

What is another name for the chorionic cavity

A

extraembryonic coelom

17
Q

What forms the chorionic cavity

A

Cavities in extra embryonic mesoderm coalesce (become bigger and join)

18
Q

What does the extra embryonic mesoderm cover now

A
  • amnion and yolk sac

- lines the trophoblast

19
Q

What are the two layers of mesoderm joined by

A

connecting stlk

20
Q

What happens in the second week summary

A
  • 2 layer (ectoderm and endoderm)
  • 2 cavities (amniotic and yolk sac)
  • 2 trophoblast derivatives (cytotrophoblast and syncytiotrophoblast)
21
Q

How is the intraembryonic mesoderm formed

A

Ectodermal cells begin to divide and migrate between ectoderm and endoderm in the region of the primitive streak (the bump on the blue cells where the endoderm and ectoderm meet) to form the intraembryonic mesoderm

22
Q

How is the prechordal plate formed

A

Endoderm thickens (yellow) and becomes firmly adherent to overlying ectoderm in the region of the prochordal plate

23
Q

What is the future mouth region of the foetus

A

Prochordal plate

24
Q

How is the notochord formed

A

Cells from the head end of the primitive streak form the notochord

25
What does the notochord do
Induces overlying ectoderm to form the neuroectoderm of the neural plate
26
Why does the embryo lengthen
Cell production in and migration from the primitive streak
27
What does the primitive streak form
Mesoderm continues to be produced and migrates laterally until it joins up with the extra-embryonic mesoderm
28
How is the septum transversum formed
When the mesoderm migrates forwards (to the top)
29
What does the cloacal plate form
Anal end of gut
30
What is the structure that separates the endoderm and ectoderm apart from where they touch (prochordal plate)
Intraembryonic mesoderm
31
How is the neural tube formed
Neural plate forms neural folds which eventually fuse to form neural tube
32
What does the neural tube form
brain and spinal chord
33
What is formed in the third week summary
-3 germ layers -3 important structures: primitive streak notochord neural tube