Lecture 9: Development of the Embryo/Fetus (1)

Question 1

How far down the fallopian tube does fertilization generally occur? And if it occurs outside of this, what is it called?

Answer 1

• 1/3 of the way from the ovary to the uterus

- An ectopic pregnancy

Question 2

What are the main week 1 events of embryological development?

Answer 2

• Cleavage and formation of the morula (within 24 hours)
• Compaction (days 3-4) and embryoblast and trophoblast
• Formation of the blastocyst (days 4-5) and blastocoel fluid due to trophoblast
• Implantation (day 6)

Question 3

When do the synctiotrophoblast and cytotrophoblast form?

Answer 3

Days 6-9

Question 4

When do the epiblast and hypoblast form?

Answer 4

By day 8 it is completed

Question 5

When and how does the amniotic cavity form?

Answer 5

Starts at Day 8- fluid fills between the cells of the epiblast and the cells of the overlying trophoblast

Question 6

What 3 key events happens during day 9?

Answer 6

1. The primary yolk sack is formed by a proliferation and migration of hypoblast.
2. Extraembryonic mesoderm fills the blastocoel
3. The chorionic cavity forms from the extraembryonic mesoderm

Question 7

At day 13, the connecting stalk forms. Is it formed from the epiblast?

Answer 7

NO! It is from the extraembryonic mesoderm

Question 8

When do trophoblastic lacunae form and where?

Answer 8

Day 9 and in the synctiotrophoblast