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0

Define the pre-embryonic, embryonic and fetal stages

0-2,2,8,9-38

1

What is clevage?

30 hours after fertilaisation Zygote divides into 2 blastomeres, these keep dividing to form the morula a ball of cells

2

What is compaction?

Differentiation of morula into blastocyst with inner cell mass (embryoblast) and outer cell mass (trophoblast)

3

What is the zona pellucida?

Glycoprotein shell to prevent polyspermy, disappears on day 5

4

Discuss week 1

Development from zygote to morula via clevage
Morula to blastocyst via compaction
Hatch from zona pellucida
Totipotent - pluripotent
Now 107 cells - 8- embryo, 99 - fetal membrane

5

Discuss week 2

Differentiation of embryoblast into epi and hypoblast
Trophoblast into syncitiotrophoblast and cytotrophoblast
Forms bilaminar disc and amniotic cavity

Implantion
Formation of primitive yolk sac by heusers membrane
Primitive yolk sac pulled away from cytotrophoblast
Maternal sinusoids join with syncitiotrophoblast
Formation of secondary yolk sac
Formation of chorionic cavity by fusion of spaces in extraembryonic mesoderm

6

Define blastocyst

Formed when morula undergoes compaction has inner cell mass(embryoblast) and outer (trophoblast)

7

describe the trophoblast

r cell mass, from support structures for embryo

8

describe the embryoblast

inner cell mass107 cells 8 go onto form embryo

9

describe the syncitiotrophoblast

derivative from trophoblast, cells that invade maternal sinusoids resulting in uteroplacentalirculation

10

describe the cytotrophoblast

derivative of trophoblst, placental membrane ound yolk sac