Cleavage, Blastulation, and Implantation

Question 1

when is the morula formed?

Answer 1

day 4

Question 2

true or false

The morula’s cells are totipotent

Answer 2

true

only the morula’s cells are totipotent

Question 3

when is the blastocyst formed?

Answer 3

day 5

Question 4

when does a zygote first differentiate?

Answer 4

during blastulation

Question 5

true or false

The cells of a blastocyst are totipotent.

Answer 5

false

they are pluripotent

Question 6

what happens on day 7?

Answer 6

1- the trophoblast differentiates into cytotrophoblasts and syncytiotrophoblasts and begins to implant into the endometrium
2- the inner cell mass differentiates into hypoblasts and epiblasts, forming a bilaminar disc

Question 7

what happens on day 8?

Answer 7

1- the amniotic cavity begins to form
2- the syncytiotrophoblast expands (-> there’s a significant progress in implantation)

Question 8

what happens on day 9?

Answer 8

1- cells migrate from the hypoblast, forming Heuser’s membrane
2- lacunae form with the syncytiotrophoblast
3- implantation is complete
4- the syncytiotrophoblast surrounds the embryo

Question 9

what happens on day 10?

Answer 9

1- extraembryonic mesoderm forms
2- trophoblastic lacunae fill up with maternal blood, forming the first real connection between the mother and embryo (->positive pregnancy test result)
3- syncytiotrophoblast produces the human chorionic gestation hormone

Question 10

what happens on day 11?

Answer 10

1- only two cavities are present:
a- amniotic cavity
b- primary yolk sac
2- extraembryonic mesoderm fully surrounds the embryo

Question 11

what happens on day 12?

Answer 11

the extraembryonic mesoderm splits to form the chorionic cavity

Question 12

what happens on day 13?

Answer 12

cells migrate from hypoblast to form secondary yolk sac, pushing the primary yolk sac aside as it begins to degenerate

the secondary yolk sac is also known as the definitive yolk sac

Question 13

what happens on day 14?

Answer 13

primary yolk sac is reduced to a remnant at the abembryonic pole of the chorionic cavity

abembryonic: the pole that is away from the embryo

Question 14

what happens on day 15?

Answer 14

the embryo is attached to the chorion by the connecting stalk

Question 15

what are the four extraembryonic structures?

Answer 15

1- yolk sac
2- amnion
3- chorion
4- allantois

Question 16

what are the functions of the yolk sac?

Answer 16

1- formation of primordial germ cells
2- hematopoiesis