Female Reproductive Physiology

Question 1

during sexual differentiation into female, the absence of what 2 hormones causes what important things to happen?

Answer 1

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

Question 2

when do FSH and LH peak during a female’s life? (2)

Answer 2

2-6 months of post-natal age and before menarche

Question 3

when does the number of oogonia in the fetal ovary peak?

Answer 3

at 6 months of fetal development

Question 4

what hormones stimulate the production of oogonia in the ovaries?

Answer 4

hCG from the placenta and fetal FSH and LH

Question 5

what is the function of aromatase?

Answer 5

converts testosterone to estrone or estradiol, the primary secretory products of the ovary

Question 6

how is estriol made?

Answer 6

estrone or estradiol is converted to estriol in the liver

Question 7

which sex hormones are mostly bound to albumin?

Answer 7

estrogen, androstenedione

Question 8

describe the steps of female puberty

Answer 8

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

Question 9

what hormone induces closure of growth plates in long bones in girls?

Answer 9

estrogen

Question 10

what happens when pregnancy does not happen at the end of the menstrual cycle?

Answer 10

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

Question 11

what hormone induces maturation of follicles during the menstrual cycle?

Answer 11

FSH

Question 12

what happens when a dominant follicle forms during the menstrual cycle?

Answer 12

it begins to secrete estrogen autonomously –> FSH is decreased via negative feedback –> atresia of non-dominant follicles

Question 13

what happens when estrogen peaks during the menstrual cycle?

Answer 13

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

Question 14

what does the corpus luteum do once it forms?

Answer 14

produces enormous amounts of progesterone –> inhibits LH and FSH secretion

Question 15

role of inhibin

Answer 15

produced by the ovary and selectively inhibits FSH release –> FSH surge not as large as LH surge

Question 16

role of theca cells in ovary

Answer 16

under the control of LH, produce androgens that diffuse into granulosa cells

Question 17

role of granulosa cells in ovary

Answer 17

FSH stimulates granulosa cells to stimulate aromatase activity, which converts androgens (from theca cells) to estrogens

Question 18

what hormone predominates during the luteal phase of the menstrual cycle?

Answer 18

progesterone

Question 19

what hormone predominates during the follicular phase of the menstrual cycle?

Answer 19

estrogen

Question 20

which phase of the menstrual cycle does the proliferative phase occur in? what happens during the proliferative phase?

Answer 20

follicular phase; growth of myometrium stimulated by estrogens

Question 21

which phase of the menstrual cycle does the secretory phase occur in? why?

Answer 21

luteal phase due to progesterone from the corpus luteum

Question 22

what leads to menstrual bleed?

Answer 22

uterine spiral artery vasoconstriction is signaled by the decline of progesterone at the end of the luteal phase –> sloughing of myometrium

Question 23

implantation within the wall of the uterus occurs __ days after _____

Answer 23

6; fertilization

Question 24

pregnancy: ______ secrete hCG, which is detectable in blood _____ after conception and on home test in urine _____ after conception

Answer 24

syncytiotrophoblasts (of placenta); 1 week; 2 weeks

Question 25

blastocyst enters uterine cavity __ days after _____

Answer 25

5; LH peak

Question 26

what hormone rescues the corpus luteum and how?

Answer 26

hCG maintains corpus luteum (and thus progesterone) for first 8-10 weeks of pregnancy by acting like LH (otherwise no luteal cell stimulation –> abortion)

Question 27

why do menstrual cycles stop during pregnancy?

Answer 27

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

Question 28

what enzyme converts cholesterol to pregnenolone?

Answer 28

cholesterol desmolase

Question 29

what enzyme converts pregnenolone to progesterone?

Answer 29

3beta-hydroxysteroid dehydrogenase

Question 30

which enzyme is plentiful in the placenta and what is its function?

Answer 30

aromatase; converts androgen to estrogen

Question 31

what can be measured in maternal blood as index of fetal distress?

Answer 31

estriol

Question 32

when does hCG peak and why does it wane during pregnancy?

Answer 32

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

Question 33

hCG has homology with what other hormones? in what subunit?

Answer 33

LH, FSH, TSH; alpha

Question 34

functions of oxytocin (2)

Answer 34

1. promotes uterine contractions

2. assists in milk let-down

Question 35

how does lactation start, and what is needed to maintain it?

Answer 35

after labor, the decrease in progesterone and estrogen disinhibits lactation; suckling causes nerve stimulation and oxytocin and prolactin production

Question 36

how does prolactin inhibit ovulation in females? what does the same mechanism do in males?

Answer 36

prolactin inhibits GnRH synthesis and release; inhibits spermatogenesis in males

Question 37

why does estrogen production decrease in menopause?

Answer 37

age-linked decline in ability of ovaries to produce mature follicles

Question 38

hormonal changes of menopause (3)

Answer 38

decreased estrogen, large increase in gonadotropins (FSH > LH) due to loss of negative feedback via estrogen, increased GnRH

Question 39

how do reproductive events/disorders cause osteoporosis?

Answer 39

loss of gonadal steroids removes the anti-resorptive effects of these hormones –> loss of bone mineral that leads to osteopenia/osteoporosis