AN S 345 Lecture 12: AnS345_Week3-4_Lectures
20 Mar 2017
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Document Summary
Types of placentas diffuse- simple takes up large amount of space, lots of small attachments. Especially in the pig the placenta has to be much larger to make up for the difference in the attachment complex. Not as complicated as a cow cotyledonary discoidal maternal recognition of the placenta occurs in the first few weeks of pregnancy elongation --> formation of yolk sac --> amniotic folds enclose embryo --> formation of the chorioallantoic placenta. Placenta- an organ that allows metabolic exchange between the dm and the fetal components. Gonadotrophins , progesterone aids in maternal recognition so the dam does not miscarry the antigenic individuality if the embryo is protected and maintained. The embryos gonads and maternal recognition influence by most factors that alter embryo or fetus size. Multiparous animals, number of fetuses/embryos present in the litter is inversely proportional to both the fetus and the placenta size.
