Placenta Anatomy

Question 1

list the 4 basic fetal membranes

Answer 1

1. chorion
2. amnion
3. yolk sac
4. allantois

Question 2

how do the basic fetal membranes combine to form the chorion, the placenta, and the yolk placenta?

Answer 2

the chorion: trophoblast + mesoderm

yolk sac + chorion = choriovitelline placenta/yolk sac placenta, the earliest, most primitive placenta

allantois + chorion = allantochorion/chorioallantoic placenta, the true placenta formed later after the yolk sac placenta, contacts the endometrium

Question 3

list the 3 fluid filled cavities of the developing embryo and fetus and understand the spatial relationships of the fetus to these fluid filled cavities

Answer 3

1. amniotic cavity: grows out of foregut, will surround fetus, hold baby pee
2. allantoic cavity: grows out of hindgut region, will surround all structures within the placenta
3. yolk sac cavity: grows out of midgut, smallest cavity

Question 4

list the macroscopic (gross) types of chorioallantoic placentae in the bitch, ruminants, and mare

Answer 4

1. zonary placenta: in the bitch and queen
2. bovine: macrocotyledeonary
3. mare: microcotyledonary

Question 5

ID the amniotic membrane in bitch, cow, and mare

Answer 5

this is what the fetus emerges in! during parturition, the fetus feet break through the chorioallantoic membrane for exit, but only exit in the amniotic sac so that the CAM can continue providing oxygen to the fetus throughout parturition; CAM will be expelled after the fetus is out

Question 6

ID the yolk sac and chorioallantoic placenta in the bitch

Answer 6

see pictures

Question 7

ID the chorioallantoic placentas in the cow and mare

Answer 7

see pictures