EEM

Question 1

What are the four EMM?

Answer 1

Chorion
Allantois
Amnion
Yolk sac

Question 2

What does the chorion do?

Answer 2

have vili and BV
first to develop foetal side from trophectoderm
allantois fuses with chorion = choir-allantoic placenta
Trophoblasts enter maternal tissue and form inner cytophoblast and outer syncytiotrophoblast layers

Question 3

What is the allantois?

Answer 3

Incontast with bladder and lets excreted fluids be taken to placenta and enter maternal circulation
Egg forming animals = larger as no placenta
Mammals = small as chorion-allantois transports to placenta

Question 4

What does the amnion do ?

Answer 4

secrete amniotic fluid (5 weeks in man)
expands to adhere to inner surface of chorion
Fluid allows free movement of foetus, protection and temp maintenance

Question 5

What does the yolk sac do?

Answer 5

Early nutrient transfer
important in man up to 3 months as nutrients absorbed into yolk sac. Only point of transfer in reptiles
Vascular components = preliminary circulatory cells develop
First site of blood vessel endothelial development