Flashcards in Female Reproductive Physiology Deck (39):
during sexual differentiation into female, the absence of what 2 hormones causes what important things to happen?
absence of androgens and MIF (mullerian-inhibiting factor) --> Wolffian ducts regress and male genitalia do not form, and the mullerian ducts develop into the female reproductive tract
when do FSH and LH peak during a female's life? (2)
2-6 months of post-natal age and before menarche
when does the number of oogonia in the fetal ovary peak?
at 6 months of fetal development
what hormones stimulate the production of oogonia in the ovaries?
hCG from the placenta and fetal FSH and LH
what is the function of aromatase?
converts testosterone to estrone or estradiol, the primary secretory products of the ovary
how is estriol made?
estrone or estradiol is converted to estriol in the liver
which sex hormones are mostly bound to albumin?
describe the steps of female puberty
GnRH pulses commence at about 9 year of age --> increase in FSH and LH --> restart ovarian follicular development and production of estradiol by steroidogenic tissue --> estrogen leads to growth spurt and secondary sex characteristics
what hormone induces closure of growth plates in long bones in girls?
what happens when pregnancy does not happen at the end of the menstrual cycle?
the corpus luteum dies and progesterone and estrogen decrease (because hCG is not released by a trophoblast) --> FSH increases due to loss of negative feedback
what hormone induces maturation of follicles during the menstrual cycle?
what happens when a dominant follicle forms during the menstrual cycle?
it begins to secrete estrogen autonomously --> FSH is decreased via negative feedback --> atresia of non-dominant follicles
what happens when estrogen peaks during the menstrual cycle?
it induces a switch in the hypothalamic-pituitary unit from negative to positive feedback so that estrogen stimulates a surge in LH --> ovulation and formation of corpus luteum
what does the corpus luteum do once it forms?
produces enormous amounts of progesterone --> inhibits LH and FSH secretion
role of inhibin
produced by the ovary and selectively inhibits FSH release --> FSH surge not as large as LH surge
role of theca cells in ovary
under the control of LH, produce androgens that diffuse into granulosa cells
role of granulosa cells in ovary
FSH stimulates granulosa cells to stimulate aromatase activity, which converts androgens (from theca cells) to estrogens
what hormone predominates during the luteal phase of the menstrual cycle?
what hormone predominates during the follicular phase of the menstrual cycle?
which phase of the menstrual cycle does the proliferative phase occur in? what happens during the proliferative phase?
follicular phase; growth of myometrium stimulated by estrogens
which phase of the menstrual cycle does the secretory phase occur in? why?
luteal phase due to progesterone from the corpus luteum
what leads to menstrual bleed?
uterine spiral artery vasoconstriction is signaled by the decline of progesterone at the end of the luteal phase --> sloughing of myometrium
implantation within the wall of the uterus occurs __ days after _____
pregnancy: ______ secrete hCG, which is detectable in blood _____ after conception and on home test in urine _____ after conception
syncytiotrophoblasts (of placenta); 1 week; 2 weeks
blastocyst enters uterine cavity __ days after _____
5; LH peak
what hormone rescues the corpus luteum and how?
hCG maintains corpus luteum (and thus progesterone) for first 8-10 weeks of pregnancy by acting like LH (otherwise no luteal cell stimulation --> abortion)
why do menstrual cycles stop during pregnancy?
hCG stimulates estrogen and progesterone release from the corpus luteum which inhibits gonadotropic secretion preventing menstrual cycles during pregnancy and stimulates continued growth of the endometrium to nurture the growing implanted embryo and fetus
what enzyme converts cholesterol to pregnenolone?
what enzyme converts pregnenolone to progesterone?
which enzyme is plentiful in the placenta and what is its function?
aromatase; converts androgen to estrogen
what can be measured in maternal blood as index of fetal distress?
when does hCG peak and why does it wane during pregnancy?
first trimester of pregnancy; because placenta is responsiblef or most of the estrogen and progesterone in 2nd and 3rd trimesters and corpus luteum is no longer necessary
hCG has homology with what other hormones? in what subunit?
LH, FSH, TSH; alpha
functions of oxytocin (2)
1. promotes uterine contractions
2. assists in milk let-down
how does lactation start, and what is needed to maintain it?
after labor, the decrease in progesterone and estrogen disinhibits lactation; suckling causes nerve stimulation and oxytocin and prolactin production
how does prolactin inhibit ovulation in females? what does the same mechanism do in males?
prolactin inhibits GnRH synthesis and release; inhibits spermatogenesis in males
why does estrogen production decrease in menopause?
age-linked decline in ability of ovaries to produce mature follicles
hormonal changes of menopause (3)
decreased estrogen, large increase in gonadotropins (FSH > LH) due to loss of negative feedback via estrogen, increased GnRH