Development of the Embryo

Question 1

Approximately how long after fertilisation does the implanted blastocyst start to differentiate into different types of cells?

Answer 1

~ 1 week

Question 2

Describe what happens to the embryoblast.

Answer 2

Splits into two, with the yolk sac on one side and the amniotic cavity on the other.

Question 3

What sits between the yolk sac and the amniotic cavity?

Answer 3

Embryonic disc, which develop into the foetal pole, and eventually into the foetus.

Question 4

What surrounds the embryoblast complex?

Answer 4

Chorion

Question 5

What are the two layers of the chorion?

Answer 5

1. Cytotrophoblast (inner layer)

2. Syncytiotrophoblast (outer layer embedded in endometrium)

Question 6

What does the connecting stalk eventually become?

Answer 6

Umbilical cord.

Question 7

When does the embryonic disc develop into the foetal pole?

Answer 7

~ 5 weeks gestation

Question 8

What are the three layers of the foetal pole?

Answer 8

1. Ectoderm (outer layer)
2. Mesoderm (middle layer)
3. Endoderm (inner layer)

Question 9

List 6 tissues the endoderm forms.

Answer 9

1. GI tract
2. Lungs
3. Liver
4. Pancreas
5. Thyroid
6. Reproductive system

Question 10

List 6 tissues the mesoderm forms.

Answer 10

1. Heart
2. Muscle
3. Bone
4. Connective tissue
5. Blood
6. Kidneys

Question 11

List 5 tissues the ectoderm forms.

Answer 11

1. Skin
2. Hair
3. Nails
4. Teeth
5. Central nervous system

Question 12

When does the foetal heart form and start to beat?

Answer 12

~ 6 weeks gestation

Question 13

When have all the major organs began to develop?~

Answer 13

~ 8 weeks gestation