Gastrulation, formation and derivatives of germinal layers. Folding of the embryo.(Body axes, cranio-caudal and dorsoventral differentiation.)

Question 1

What happen during weak 1?

Answer 1

1. ovulation
2. fertilization
3. cleavage
4. migration toward the uterine cavity
5. Blastocyst composed of trophoblasts and embryoblasts is formed by the end of this week.

Question 2

What is blastocyst composed of? (Week 1)

Answer 2

Blastocyst composed of trophoblasts and embryoblasts is formed by the end of this week.

Question 3

Name of this embryo

Answer 3

BILAMINAR EMBRYO

Question 4

What happen outside of bilaminar embryo during week 2?

Answer 4

differentiation of throphoblasts, invasion, destruction of maternal vessels, hCG (stops the menstrual cycle).

Question 5

What happen inside of bilaminar embryo during week 2?

Answer 5

• differentiation of amnioblasts, epiblasts, hypoblasts
• formation of the amniotic cavity and the yolk sac
• appearance of extraembryonic mesoderm

Question 6

How is the trilaminar embryo made?

Answer 6

Gastrulation (Week 3 & 4)

Question 7

What happens in the germ layers?

Answer 7

differentiation of germ layers

Question 8

How is the (almost) final shape of the embryoachieved?

Answer 8

folding

Question 9

What is intraembryonic mesoderm? How is it formed?

Answer 9

Bilaminar embryo is transformed into a trilaminar disc by theappearance of the middle layer

Question 10

(1)___ proliferate and migrate until they collide in the midline.

→ As a result of this collision, the primitive node/pit and (2)____ appears

Answer 10

1. Epiblasts
2. the primitive streak

Question 11

How does polarization happen during gastrulation?

Answer 11

Epiblasts proliferate and migrate until they collide in the midline. As a result of thiscollision, the primitive node/pit and the primitive streak appears

Question 12

Some proliferating epiblasts (I) persist in their original layer and form (1)___

Others invaginate along the primitive pit and primitive streak and (II) either spread between the original epiblast and hypoblast layers to give the (2)____, or (III) completly replace the original hypoblastsand transforme into (3)___

Answer 12

1. the ectoderm.
2. intraembryonic mesoderm
3. the definitive endoderm

Question 13

Some proliferating epiblasts (I) persist in their ___ layer and form the ectoderm

Answer 13

original

Question 14

Some proliferating epiblasts invaginate along ___ (2 things) and (II) either spread between the original epiblast and hypoblast layers to give the intraembryonic mesoderm

Answer 14

the primitive pit and primitive streak

Question 15

Some proliferating epiblasts invaginate along the primitive pit and primitive streak and (II) either spread between ____ (2 layers) to give the intraembryonic mesoderm

Answer 15

the original epiblast and hypoblast layers

Question 16

Some proliferating epiblasts (I) persist in their original layer and form theectoderm.

Others invaginate along the primitive pit and primitive streak and (II) either spread between the original epiblast and hypoblast layers to give the intraembryonic mesoderm, or (III) completly replace ___ and transform into the definitive endoderm.

Answer 16

the original epiblast and hypoblast layers

Question 17

Epiblasts invaginating at ___ move anteriorly between the epiblast and hypoblast layers and form the axis of the intraembryonic mesoderm: the notochord

Answer 17

the axis of the intraembryonic mesoderm: the notochord

Question 18

Epiblasts invaginating at ___ move anteriorly between the epiblast and hypoblast layers and form the axis of the intraembryonic mesoderm: the notochord

Answer 18

the primitive pit

Question 19

Epiblasts invaginating at the primitive pit move anteriorly between ____ (2 layers) and form the axis of the intraembryonic mesoderm: the notochord

Answer 19

the epiblast and hypoblast layers

Question 20

Epiblasts invaginating at the primitive pit move anteriorly between the epiblastand hypoblast layers and form the axis of the intraembryonic mesoderm: the notochord.

→ (1)____ moves backward and (2)____ shortens, while (3)____ is getting longer and longer. Anterior to the notochord theprechordal plate develops.

Answer 20

1. The primitive pit
2. the primitive streak
3. the notochord

Question 21

Epiblasts invaginating at the primitive pit move anteriorly between the epiblastand hypoblast layers and form the axis of the intraembryonic mesoderm: the notochord.

→ The primitive pit moves backward and the primitive streak shortens, while the notochord is getting longer and longer.

→ Anterior to the notochord ____ develops.

Answer 21

1. The primitive pit
2. the primitive streak
3. the notochord

Question 22

Identify

Answer 22