BIOL30001 Lecture Notes - Lecture 16: Amniotic Sac, Yolk, External Fertilization
16 Oct 2018
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Document Summary
Embryos develop outside mother"s body (good for mother) with nutrients coming from the egg yolk. Must have internal fertilisation embryos develop within mother"s body and are born as miniature copies of the adult. Outer shell for protection, gas exchange; a thin membrane under the shell also allows for gas exchange. That surround the embryo and form the amniotic sac. Amnion secretes a u that bathes and protects the embryo from drying out. Or dependence of pregnancy on maternal placental function don"t really need an ovary after a certain period of time (placenta produces progesterone, not cl in ovary) for human, monkey, sheep and horse (long pregnancy duration) Major placenta types: di uses e. g. pig, horse, camel, cotyledonary e. g. sheep, cow, zonary e. g. dog, goes right around uterus, discoid e. g. human. De ned by the number of layers between the maternal and foetal blood: maternal endometrial epithelium intact. Removal of maternal epithelium, endothelium/blood vessel and connective tissue.
