Female Reproductive Physiology Flashcards
How many chromosomes does a primary oocyte have in a female?
46 - it’s tetraploid
How many chromosomes does a secondary oocyte have?
23 - it’s still diploid until it finishes meiosis II
How many primary oocytes are made?
about 2 million
About how many secondary oocytes are made?
about 200,000
About how many secondary oocytes will actually ovulate in a lifetime?
400
Where does the primary oocyte halt in the cell cycle/
meiosis 1 - stops in prophase
When is meiosis 1 completed?
in response to the LH surge prior to ovulation
Where in the cell cycle does the secondary oocyte halt?
metaphase II
When does meiosis II complete?
when the egg is fertilized
What is the term for the growth and progression of primordial follicles to preovulatory follicles?
folliculogenesis
What happens when primordial and primary follicles are exhausted?
menopause
During each cycle, about how many primary follicles are recruited to complete meiosis 1?
usually less than or equal to 7, but only one will usually become the ovulatory follicle
What does cyclic recruitment refer to?
the antral follicles that started developing along with the dominant follicle - they’re are rescued from atresia by FSH so that they continue developing during subsequent cycles
Describe the dominant follicle
it’s the largest one - produces the most hormones. it will become the ovulatory or graafian follicle
About how many menstrual cycles does it take for a follicle to fully mature?
about three
___ GnRH pulses result in the FSH and LH basal secretion.
hourly
What does FSH stimulate?
- follicle development
2. LH receptor synthesis
FSH and LH both promote synthesis of what other hormone?
estrogen
How does estrogen feed back?
negatively on both the hypothalamus and anterior pituitary
thus, makes FSH and LH secretion reduced
What other hormone will inhibit FSH secretion, but has no effect on LH secretion? Why is that important?
inhibin
important because you need a giant LH surge. FSH will also elevate, but it’s attenuated due to this inhibin. Because if you were to start a pregnancy, you wouldn’t want FSH triggering another follicle.
When does the feedback relationship between estrogen and secretion from the hypothalmus/anterior pituitary gland reverse?
when the antral follicles are large, really high levels of estrogen induce rapid GnRH pulses and the ovulatory surge in LH
(so in that case, estrogen is not inhibiting LH secretion, it’s promoting it)
What hormone is released by the hypohtalamus int his axis?
GnRH - gonadotropin releasing hormoine
What hormones does the anteiro rpituitary secrete?
FSH and LH
What ovarian cells secrete the androgens? Under what hormone influence?
the theca cells
under inluence from LH
What do the granulosa cells do to these androgens? Under what hormone influences?
produces aromatase which will convert the androgens to estrogens
under FSH
what estrogen is largely the one produced by that aromatase reaction?
estradiol 17 beta
Where in the hypothalmus is GnRH made?
arcuate nucleus
Describe the receptor for GnRH?
membrane GPCR couple to Gq
the Gq activates phospholipase C, DAG, and IP3
What are the three gondadotropins/ Which one is placental?
FSH and LH from anterior pituitary
hCG from placenta
When is hCG important?
in the first trimester, it maintains the corpus luteum, which keeps progesterone and estrogen levels high to maintain pregnancy
Why does hCG decrease in later pregnancy?
the placenta will take over steroidogensis at that point
What type of molecules are the FSH and LH and hCG hormones?
glycoproteins consisting of two subunits - similar to TSH
alpha subunit is identical in all, but beta subunit is unique
Describe the receptors for the gonadotropins?
transmembrane receptors that are Gs protein coupled
Which receptor - FSH receptor or LH receptor - will also bind hCG?
LH receptor - the LHCGR
So what cells in the follicle will have LHR?
tehcal cells
What cells in the follicle will have FSHr?
Granulosa cells
What are the two estrogen receptors? which one mediates the HPO axis?
ERalpha
ERbeta
ERalpha is the main one for this axis and reproduction
E2 is what binds ERalpha. Does it usualy do this on the surface or in the cytoplasm?
does both, but mostly in the cytoplasm - remember it’s a steroid hormone
Small increases in the secretion of the gonadotropins will lead to what?
follicular growth and an increase in synthesis of secretory and ovarian steroid hormones
this is the follicular phase
What happens to extrogen and progesterone in the follicular phase?
estrogen levels are higher than progesteron, and they go up waaaay up prior to ovulation - remember this is what stimulates the LH surge
WHat happens to estrogen immediatly after ovulation?
decrease, but then go back up with luteal development
During early to mid-luteal phase, the high levels of estrogen, progesterona nd inhibin from the CL will do what to the HPO axis?
inhibit release of GnRH, TSH and LH
In the late luteal phase, the CL undergoes regression, so estrogen and progsteron levels decrease, which stimualtes what?
menstruation and FSH and LH will trigger the next follicular phase
What two phases of the uterine cycle occur during the follicular phase?
menses and proliferative phase
What phase of ht euterine cycle occurs during the luteal phase?
secretory phase (prep for a pregnancy)
Prevention of the LH surge will prevent what?
ovulation
What marks the first day of the ovarian/uterine cycle?
onset of menses
Ovulation typically occurs on what day?
day 14
What does estrogen trigger in the endometrium during follicular phase
thickening and proliferation - develop from cuboidal to speudostratiied
stromal and vessel growth
uterine lining increases tenfold
What does progesterone do to the endometrium?
halts further growth
causes secretion from glands as opposed to proliferation
With ovulation, you have movement of egg into the fallopian tube. Where in the tube does fertilizaiton usually occur?
in the ampulla
the embryo implants at what stage? at what day?
balstocyst - usually day 6 (but between 5 -9)
What are the hormones created by the palcenta?
progesteron
estradiol 17b
human placental lactogen
inhigin
hCG maintains the corpus luteum until about what month?
3-4
Urinary hCG can be used as a pregnancy indicator about how many days post ovulation?
10 days - accuracy best at 1 week past the first day of expected period
THe transition between uterine dependence on ovarian versus placental steroids marks what interval
the interval with the greatest likelihood of miscarriage
Teleologically, why do you want progesteron>estrogen for the first half of pregnancy?
progesterone causes hyperpolarizaitn of myometrial cells to prevent contractions by:
- decreasing adrenergic receptors
- inhibiting oxytocin receptor synthesis
- inhibit Estrogen receptor synthesis
- promotes storage of PG synthesizing enzymes so you don’t get synthesis (prostaglandins also trigger contractions)
Teleologically, why would you want estrogen>prostaglandins in later pregnancy?
estrogen increases oxytocin receptors, promtoes uterine contractility, cervical ripening, increases local prostaglandin release from the placenta which causes myometrial contraction
What two progstalgnainds predominate in reproduction?
PGF2alpha
PGE
What two things are the prostaglandins involved in for the regular menstrual cycle?
- rupture of graafian follicle at ovulatoin
2. contraction of myometrium during menstruation
What else will the prostaglandins do during pregnancy?
braxton hicks
strong utering contractions during parturition
What secretes oxytocin?
posterior pitutiay
What does oxytocin stimualte?
smooth muscle contraction in the uterus and breasth
Does oxytocin have positiev or negative autoregulation within the hypothalamsu?
positive
What causes OT release at the end of gestation?
mechanical stimulation of the cervix
forceful uterine contractions during parturition
What hormones is mamogenesis dependent on?
estrogen, glucocorticoids, andsomatotropin will cause development of the epithleial ductal tree (during puberty)
also progesterone and prolactin to get lobular alveolar growth
During pregnancy, you get lactogenesis I. what happens?
lobular-alveolar growth - preparation for lactation
What happens in lactogenesis II?
post-partum onset of copious milk secretion (which comes with the fall of progesterone after parturition)
What hormone is lactogenesis II dependent on?
prolactin
What’s the term for maintenence of lactation?
galactopoiesis
What hormone is necessary for milk ejection or let-down?
oxytocin
What will cause involution of lactation?
lack of prolactin
due to lack of suckling
