Week 2: Implantation And Formation Of Bilaminar Germ Disc

Question 1

Decidualization of the stroma is initiated by

Answer 1

Implantation of the embryo

Question 2

Implantation is completed in week 2.(true or false)

Answer 2

True

Question 3

Decidualization of the embryo leads to the formation of the maternal components of the placenta. (True/ false)

Answer 3

True

Question 4

Mention the major events of day 8.

Answer 4

1. The blastocyst embeds into the endometrial stroma
2. The cytotrophoblast and the syncytiotrophoblast begin to form
3. Cells in the inner mass begin to differentiate into the bilaminar germ disc which comprises of the hypoblast layer and epiblast layer
4. In the epiblast a small cavity begins to appear
5. The large tortuous glands secrete abundant glycogen and mucus.

Question 5

Mention the major events of day 9.

Answer 5

1. The blastocyst deeply embeds into the endometrium and the penetration defect is closed by a fibrin coagulum.
2. The trophoblast develops further with most progress on the embryonic pole where a vacuole appears.
3. Lacunae begin to form
4. At the abembryonic pole the cells of the hypoblast differentiate into thin cells that form a membrane that lines the inner surface of the cytotrophoblast calked the exocoelomic membrane or Heuser’s membrane
5. The primitive yolk sac is formed
6. The amnionic cavity is also enlarged and fills with amnionic fluid

Question 6

Mention the major events of day 11-12.

Answer 6

1. Implantation is complete
2. Lacunae are fully formed
3. Invasion of the maternal sinusoids at the embryonic pole begins
4. The uteroplacental circulation is formed
5. New cells appear in between the inner cytotrophoblast and the outer surface of the exocoelomic cavity called the extraembryonic mesoderm
6. The extraembryonic coelom(chorionic cavity) forms
7. The chorionic cavity covers the primitive yolk sac except where the bilaminar germ disc is connected to the trophoblast by a connecting stalk
8. The extraembryonic mesoderm lining the cytotrophoblast and amnion attain the name extraembryonic somatopleuric mesoderm
9. Cells in the endometrium undergo decidualization

Question 7

Mention the events of day 13.

Answer 7

1. The fibrin coagulum is disappeared
2. The trophoblast is characterized by villous structures called primary villi
   3.