AN SC312 Lecture Notes - Lecture 22: Yolk Sac, Trophoblast, Allantois
23 Mar 2018
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Document Summary
In mammals it doesn"t have an actual yolk but contributes in other ways. Has villi and interacts with endometrium to attach. Stops embryo from adhering to anything because of fluid. Trying to collect embryo at this stage it"s like spaghetti. Should collect around day 10 in pigs and day 13 in cattle. After yolk sac develops the trophoblast becomes the trophectoderm. All erosion of maternal side and only 3 layers on fetal side. The fetus sits in a pool of maternal blood. Causes them to be more susceptible to maternal hemorrhaging. Usually have necrotic tips on placenta in sows and mares. Placenta will break down or die off slowly. Means there is a little bit of erosion on maternal side and then re-growing. Broken down to a. a and then transported across. Mom will breakdown her own muscle to give a. a to fetus.
