Download Lesson 11

Review:
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journey of egg and sperm
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twins
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stages of embryonic development
Dec 15­7:57 AM
Primary Membranes
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these are membranes that are not part of the embryo
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they support, nourish, and protect developing embryos
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all animals have these membranes in one form or another
* See diagram on page 509
Dec 15­7:59 AM
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Primary Membranes:
Dec 15­8:01 AM
Chorion Membrane
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in chicken embryos it is located next to the shell and involved in gas exchange
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in human embryos it is the outer most membrane surrounding the fetus
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small finger like projections called chorionic villi form on the chorion and extend into the uterine lining to form the placenta
Dec 15­7:27 PM
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Amnion Membrane
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in chicken embryos it provides the liquid environment
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in human embryos it is the inner­most membrane which completely surrounds the embryo
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it is filled with amniotic fluid that protects the fetus and provides a stable envrionment
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during childbirth it provides a slippery path for the baby
Dec 15­7:30 PM
Yolk Sac and Allantois
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in chicken embryos the yolk sac surrounds the yolk which provides the food for the developing embryo while the allantois collects waste
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in human embryos they both form the umbilical cord
Dec 15­7:32 PM
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Dec 15­7:45 PM
Placenta
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a temporary organ produced by embryonic development that attaches to the wall of the uterus at the site of implantation
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allows the exchange of nutrients, oxygen and waste between mother and baby
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it secretes estrogen and progesterone preventing the break down of the corpus luteum
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this results in no menstruation and progesterone levels remain high maintaining the uterine lining, preventing development of new follicles and preparing milk ducts for milk production Dec 15­7:35 PM
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Dec 15­7:49 PM
Umbilical Cord
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rope like structure between fetus and placenta
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contains blood vessels from mom and fetus
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blood is not actually mixed
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however the diffusion of harmful chemicals (teratogens) such as drugs and alcohol can occur
Dec 15­7:39 PM
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Dec 15­7:49 PM
Quiz Review
Read Pages 500 ­ 509
Questions: Page 505 #'s 1,3,6,7,
Page 514 #'s 1,2,3,4
Page 515 #'s 8,9,10,11,12,13,14,15
http://www.pbs.org/wgbh/nova/miracle/program.html
Dec 15­7:41 PM
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