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25 Cards in this Set
- Front
- Back
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How long does implantation of the new embryo take?
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it takes about a week
usually completed by day 14 from ovulation |
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Human Chorionic Gonadotropin (hCG)
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secreted by the placenta
acts (like LH) to preserve and maintain the corpus luteum |
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corpus luteum (2)
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continues to secrete estrogens and progesterone
maintains uterine lining |
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What happens during the 2nd month through 4th month (3)
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hCG levels decline
placenta assumes the role of estrogen and progesterone production woman can miscarry |
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How long is preembryonic development?
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from fertilization until implantation
1st 2 weeks |
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cleavage
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rapid mitotic division of zygote following fertilization
NOT MEIOTIC |
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blastomeres
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daughter cells formed from cleavage
becomes smaller and smaller higher surface to volume ratio |
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When does cleavage begin?
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36 hours after fertilization
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Where does cleavage begin?
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in the UTERINE TUBE
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Morula
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cluster of 16 or more cells
developed in 3 days |
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Blastocyst (4)
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about 100 cells
4th - 5th day floats freely in uterus for 2 - 3 days fluid filled and hollow |
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trophoblasts
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outer layer of flattened cells of blastocyst
will from the placenta |
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inner cell mass
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-small cluster of rounded cells at one pole of blastocyst
-becomes embryonic disc and then embryo |
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Implantation
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attachment of blastocyte to endometrium
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window of implantation
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receptivity of endometrium is only opened by proper levels of ovarian hormones
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When does implantation occur?
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begins 6 - 7 days after ovulation
usually takes 1 week |
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proteolytic enzymes
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secreted by trophoblast cells which digest the wall (endometrium) away
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When can hCG be detected?
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1 week after fertilization
it is secreted by the trophoblast cells |
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Placenta
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temporary organ from both embryonic (trophoblastic) and maternal (endometrial) tissues
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Chorion
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come from the the trophoblast cells during placentation
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chorionic villi
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projections into uterine wall from chorion
become rich with embryonic capillaries |
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When is the placenta fully formed?
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by the end of the third month
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Embryonic Development
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weeks 2 to end of 8
Embryonic Membranes develop Gastrulation Organogenesis |
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Embryonic Membranes Develop
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develop in the first 2-3 weeks of development
chorion Inner cell mass |
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chorion forms:
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Portion of placenta
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