Implantation and formation of germ layers

Question 1

What happens when the blastocyst adheres to the endometrium

Answer 1

Implantation begins

Question 2

Where does implantation occur

Answer 2

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

Question 3

what happens to the zone pellucida in implantation

Answer 3

Disappearance of it

Question 4

What happens to the blastocyst in implantation

Answer 4

Gives rise to inner cell mass and trophoblast

Question 5

What happens in the uterine lining in implantation

Answer 5

a ‘decimal reaction’ whereby there is increased secretory function

Question 6

What does the inner cell mass form

Answer 6

The embryo and some membranes

Question 7

What color is the primitive ectoderm

Answer 7

Blue

Question 8

What color is the primitive endoderm

Answer 8

Yellow

Question 9

What does the inner cell mass give rise to

Answer 9

primitive ectoderm

Question 10

What dos the ectoderm surround

Answer 10

Amniotic cavity

Question 11

What does the endoderm surround

Answer 11

Cavity of the yolk sac

Question 12

How many layers does the blastocyst wall have

Answer 12

2

Question 13

What the trophoblast form

Answer 13

extraembryonic embryonic mesoderm

Question 14

What is the extra embryonic mesoderm

Answer 14

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

Question 15

What is the decimal reaction

Answer 15

Endometrium undergoes it

-GLycogen/lipid distended cells and glands swell more

Question 16

What is another name for the chorionic cavity

Answer 16

extraembryonic coelom

Question 17

What forms the chorionic cavity

Answer 17

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

Question 18

What does the extra embryonic mesoderm cover now

Answer 18

• amnion and yolk sac

- lines the trophoblast

Question 19

What are the two layers of mesoderm joined by

Answer 19

connecting stlk

Question 20

What happens in the second week summary

Answer 20

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

Question 21

How is the intraembryonic mesoderm formed

Answer 21

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

Question 22

How is the prechordal plate formed

Answer 22

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

Question 23

What is the future mouth region of the foetus

Answer 23

Prochordal plate

Question 24

How is the notochord formed

Answer 24

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

Question 25

What does the notochord do

Answer 25

Induces overlying ectoderm to form the neuroectoderm of the neural plate

Question 26

Why does the embryo lengthen

Answer 26

Cell production in and migration from the primitive streak

Question 27

What does the primitive streak form

Answer 27

Mesoderm continues to be produced and migrates laterally until it joins up with the extra-embryonic mesoderm

Question 28

How is the septum transversum formed

Answer 28

When the mesoderm migrates forwards (to the top)

Question 29

What does the cloacal plate form

Answer 29

Anal end of gut

Question 30

What is the structure that separates the endoderm and ectoderm apart from where they touch (prochordal plate)

Answer 30

Intraembryonic mesoderm

Question 31

How is the neural tube formed

Answer 31

Neural plate forms neural folds which eventually fuse to form neural tube

Question 32

What does the neural tube form

Answer 32

brain and spinal chord

Question 33

What is formed in the third week summary

Answer 33

-3 germ layers
-3 important structures:
primitive streak
notochord
neural tube