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20 Cards in this Set
- Front
- Back
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What are the main functions of the high estrogen and progesterone during pregnancy?
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maintain endometrium for fetus, suppress ovarian follicle development, stimulate development of breasts
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Fertilization takes place within how many hours of ovulation?
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24hrs (usu in ampulla of fallopian tube)
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When does fertilized blastocyst arrive and implant in uterine cavity?
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arrives ~4 days after ovulation, implants ~5 days after ovulation
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At the time of implantation, what does the blastocyst consist of?
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inner cell mass (becomes fetus), trophoblast (outer rim) (becomes fetal contribution of placenta), blastocyst cavity, zona pellucida (which gets broken down)
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What component of the blastocyst is responsible for invasion/implantation in the endometrium?
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syncytiotrophoblast develops finger-like projections into the endometrium, forms a sponge-like network of spaces (lacunae) that connect directly to maternal vessels
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What is responsible for the "rescue" of the corpus luteum, and when does this occur?
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the trophoblast secretes HCG (human chorionic gonadotropin) ~8 days after ovulation (thus corpus luteum continues to produce estrogen/progest)
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How is progesterone produced in the 2nd and 3rd trimesters?
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produced by placenta: cholesterol enters placenta from maternal circulation -> pregnenolone -> progesterone
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What is the major placental form of estrogen?
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estriol
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How is estriol produced in the 2nd and 3rd trimesters?
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*interplay of mother, placenta, and fetus*
cholesterol (in placenta)-> pregnenolone -> enters fetal circ -> (in fetal adrenal cortex) DHEA-sulfate -> (in fetal liver) -> 16-OH DHEA-sulfate -> (back to placenta) converted to estriol |
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What type of contractions often occur 1 month before partuition?
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Braxton Hicks contractions (uncoordinated contractions due to distention)
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What is the role of the estrogen/progesterone ratio in initiation of partuition?
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ratio increases near term
estrogen decreases threshold for contractile stimuli, and stimulates prostaglandin production (increase intracell Ca of uterine smooth muscle, thus inc contractility) |
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What is the role of oxytocin in partuition?
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still unknown; oxytocin receptors up-regulate near term, and dilation of cervix stimulates oxytocin; is used to induce labor
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What are the 3 stages of labor?
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1) uterine contractions progressively widen and thin cervix
2) fetus is delivered 3) placenta is delivered, and powerful contractions constrict uterine blood vessels to minimize bleeding |
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Why is there no lactation during pregnancy?
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estrogen and progesterone promote breast development and (est) stimulates prolactin s/c, but inhibit prolactin action
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What stimuli maintain lactation?
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suckling, which stimulates lactation and oxytocin s/c
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What are the secondary effects of prolactin?
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*inhibits ovulation*
(inhibits GnRH, thus inhibits LH/FSH, and antagonizes LH/FSH action on ovaries) |
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How do oral contraceptives work?
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estrogen and progesterone exert negative feedback on LH/FSH -> prevent ovulation and affect cervical mucus and tubal mobility
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How does the morning after pill work?
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mifepristone (RU 486) = antagonist to progesterone receptor -> prevents implantation
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What are the hormone changes that occur at menopause?
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gradual decrease in estrogen, removes feedback inhibition, and thus FSH/LH increase
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What are the common symptoms of menopause?
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thinning of vaginal epithelium, decreased vaginal secretions, decreased breast mass, accelerated bone loss, vascular instability (hot flashes), and emotional lability
(caused by loss of ovarian source of estrogen) |
