allantosis or placenta

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pistolpete007

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if they asked which structure function in excretory and respirotory function that also involved in formation of umbilical cord.....would the answer be placenta or allantosis?
 
i thought allantois, chorion, amnion, and yolk sac all form into placenta and umbilical cord. so my guess would have been allantois since placenta is an organ which is formed along with umbilical cord.

can you elaborate more on which forms into which (like other than those two)?
 
The chorion together with maternal tissue forms the placenta. The allantois forms the umbilical chord, The amnion is a sac filled with water that cusions the embryo in vertebrates. ( when a lady is preganant her water breaks, this is a ctually the amnion and the fluid that escapes is the amniotic fluid). The olk sac is found in birds and reptiles and and the membrabne digests the enclosed yolk.
 
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is not only present in birds and reptiles but also in pregnant woman. The yolk sac, is the site of early development of blood vessels, that becomes associated with the umbilical vessels.
 
Actually I think that the yolk sac becomes associated with the vitelline vessels which are different from the umbilical vessels coming from maternal circulation.