Development of extra embryonic membranes Flashcards
Amphibian egg structure?
EGg is surrounded by a gelatinous substance–> like a cytoplasm
Where are amphibian eggs?
Floating free in the a
wayer
Purpose of amphibian eggs?
Stopping the embryo from drying out
Difference between land and amphibian eggs?
Land eggs have to have a shell
STructure of land egg?
Embryo–> amniotic sac–> yolk sac–>chorion–>shell
When did mammary glands develop relative to eggs?
Prior
What did the development of a placenta allow?
Embryos to grow within the mother, and share nutrients with her
What are the cavities (layers of the extraembryonic stuff) called?
Extraembryonic coeloms
Purpose of the allantois?
Contains waste
Role of amnion?
protects embryo in a fluid filled state
Role of yolk sac?
Encloses of a reserved of nutrients
Role of chorion?
ALlows gas exchange w/ the allantois membrane
Why may fish embryos not need an allantois?
The waste products of the embryo would diffuse into the environment
What happens to the size of the yolk sac as the embryo grows?
It reduces in volume
WHat is the outer membrane in a mammalian embryos sac?
The chorion
How does the chorion attach to the uterus?
It forms villi which attach
What do the chorionic villi become?
The placenta
What happens to the amniotic cavity over time?
It grows, and moves closer to the chorion
Where do the yolk sac, allantois, amnion, chorion and placenta come from?
Tropheoderm
Different parts of a trophectoderm?
Polar trophectoderm and a mural trophectoderm
WHat does the polar trophectoderm have?
Ectoplacental cone which will develop finger like projections
What is between the amniotic cavity and the yolk sac cavity?
The primitive streak
WHat is the first element seen within the gestational sac?
Yolk sac
When is the yolk sac important?
Early embryo–> blood supply
