Female Reproductive Physiology - Meininger Flashcards
What causes the most change in steroid hormone production in girls?
Steroid hormone production results more from changes in the number or sensitivity of receptors on target cells than from changes in gonadotropin concentrations
What are the gonadotropins?
1) FSH
2) LH
What are the two modes of gonadotropin release?
1) tonic mode
2) surge mode
What is tonic mode?
1) similar to males
2) low but pulsatile release of LH
What is surge mode?
1) unique to females
2) periodic massive release of LH (ovulation)
Which set of ducts gives rise to the female reproductive system?
Mullerian ducts
What is the difference between male and female duct system development?
1) females duct system development is independent of gonadal hormones (no ovaries necessary)
2) males need testes for their development
Where are the sites of ovarian hormone production?
Ovarian follicles
What do the ovarian follicles contain?
1) oocyte
2) layers of supporting cells
3) proper hormonal environment
What kind of follicles are females born with and how do they progress?
1) born with primordial follicles
2) convert to primary follicles throughout life (independent of gonadotropins)
What step of prophase are primary oocytes arrested in until ovulation?
primary oocytes are arrested in prophase of meiosis I until ovulation
What arrests primary oocytes in Prophase of Meiosis I ?
Granulosa cell derived oocyte maturation inhibitor in the follicular fluid
What triggers the resumption of meiosis at ovulation?
LH via blockage of the inhibitor
The way gametes in the female develop…
episodically
How many follicles ovulate?
One
What happens to the follicles that are recruited but aren’t ovulated?
1) arrested in an immature state
2) undergo degeneration (atresia)
What proliferates early in the development of the follicle?
1) Granulosa cells
2) the acquire FSH receptors and produce estrogen in response to FSH
What are the steps in follicle development?
1) granulosa cell proliferation
2) further granulosa cell proliferation
3) accumulation of fluid within the follicle
4) formation of the antrum
5) ovulation - follicle ruptures and the ovum is released
6) remaining cells undergo luteinization and form the corpus luteum
What cells have FSH receptors?
Only granulosa cells
What are the main hormone products of the ovary and what produces them?
1) estradiol - by the follicle
2) progesterone - corpus luteum
What hormones are made in small amounts by the ovary?
1) androgens
a) DHEA
b) androstenedione
What hormones are made by the granulosa cells?
1) peptide hormones
a) inhibins
b) activins
2) released into follicular fluid and general circulation
Where else is inhibin made besides in granulosa cells?
1) corpus luteum
2) post ovulation
What hormones cause follicular develop after the antral phase?
FSH and LH
What are FSH required for?
1) follicular development
2) ovulation
3) luteinization
4) steroid hormone synthesis
What constitutes the ovarian cycle?
1) follicle development
2) ovulation
3) formation and degeneration of corpus luteum
What is the follicular phase?
1) part of the cycle involving follicle development
2) about 14 days but has variation
What is the luteal phase?
1) the last 14 days of the cycle fominated by the corpus luteum
2) lasts 14 days and is not variable
When does ovulation occur?
mid-cycle
What are the primary jobs of FSH and LH?
1) FSH - stimulating growth of ovarian follicles
2) LH - controls ovulation and regulates steroidogenesis
What are the two important female sex steroids?
1) estradiol - product of the follicle
2) progesterone - corpus luteum
What is the sequence of hormonal changes during the ovarian cycle?
1) FSH bump stimulates ovary
2) development of about 10 follicles
3) rising estrogen and inhibin levels supres FSH secretion
4) one dominant graafian follicle emerges and produces even more estrogen
5) peak estrogen levels stimulate secretion of LH and FSH - mid cyclic LH surge
6) ovulation
7) corpus luteum leads to progesterone production
8) if no hCG produced by the fetus to sustain corpus luteum - it regresses and progesterone and estrogen levels fall
9) FSH inhibition falls with decreased estrogen and progesterone - FSH bump…..
What do granulosa cells secrete and in response to what?
secretes estrogens in response to FSH
What does development of the follicle depend on?
production of estrogen from granulosa cells in response to the FSH bump
What kind of feedback is seen with estrogen and granulosa cells?
Positive feedback - estrogen promotes proliferation of granulosa cells and increases their responsiveness to FSH
What does estrogen and FSH do to granulosa cells?
induces granulosa cells to synthesize LH receptors and acquire sensitivity to LH
Where are LH receptors found before the antrum forms?
only on thecal cells
What effect does LH have on thecal cells?
stimulates them to produce steroids
What determines which follicles gets ovulated?
thecal cells surrounding this follicle become more sensitive to LH than other - higher receptor density
When do LH receptors appear on thecal cells and granulosa cells?
1) Thecal cells - at an early stage
2) granulosa cells - only in maturing follicle under the influence of FSH and estrogen
Why can’t granulosa cells produce estrogens and what does it need the thecal cells for?
1) deficient in androgen producing enzymes
2) rely on diffusion of androgens from thecal cells to produce estrogens
How do granulosa cells produce estrogens?
they produce aromatase in reponse to FSH and convert thecal derived androgens to estrogens
What enzymes are missing from the granulosa cell and what is its consequence?
1) 17 alpha hydroxylase and 17,20 desmolase
2) can’t convert progesterone to androstenedione (gets it from thecal cell)
What can’t the thecal cell do?
It doesn’t have aromatase activity so it can’t convert testosterone to estrogens
What is the function of granulosa cells to the oocyte and what is it analogous to in the male?
1) provides nutrients for oocyte development
2) analogous to the nurse like function of sertoli cells
What causes the release of the ovum from the follicle?
occurs as a result of proteolytic enzyme release from granulosa cells in response to LH
What are the role of progesterone and prostaglandin formation in ovulation?
1) stimulate further production of proteolytic enzymes to break down follicle wall
2) contractile events to facilitate extrusion of the ovum
What changes in granulosa cells when they become lutenized?
1) they have acquired their LH receptors
2) shift steroid production to progesterone
3) aromatase activity decreases and less estrogen is made
What keeps corpus luteum functioning and why does it have a limited lifespan?
1) maintenance of steroid production by corpus luteum depends on continued stimulation by LH
2) limited life due to decreased sensitivity to LH
How long does corpus luteum last?
1) it will regress after two weeks (even with continued LH stimulation)
2) only pregnancy and hCG rescues it
How does estrogen prime target tissues for progesterone?
1) induces progesterone receptor synthesis
2) progesterone accelerates the turnover of estrogen receptors in the same tissues and decreases their response to estrogens
What are the three phases of the uterine or endometrial cycle?
1) menstrual
2) proliferative
3) secretory
What does the proliferative phase of the uterine cycle correlate with in the ovarian cycle?
mid to late follicular phase
What happens to the uterus during the proliferative phase and what causes it?
1) under the influence of rising estrogen
2) endometrium increases in size, thickness, glands elongate and becomes vascularized
When does the secretory phase of the uterine begin and what ovarian phase does it correlate with?
1) begins of the day of ovulation
2) coincides with early to mid luteal phase of ovarian cycle
What happens to the uterus during secretory phase and what causes it?
1) progesterone and estrogen
2) endometrial glands secrete large amounts of mucus and the stroma increases in vascularity and becomes edematous
When is the peak thickness of the uterus?
1) 6-8 days after ovulation
2) preparation for the implantation of the zygote
What initiates the menstrual phase of he uterine cycle?
declining levels of steroids resulting from corpus luteum regression
What happens in the uterus during the menstrual phase?
1) necrotic changes occur in the mucosal layer due to constriction of blood supply to the endometrium
2) desquamation and sloughing of the entire functinal layer of the endometrium
3) destablization of lysosomal membranes resulting in liberation of proteolytic enzymes and increased production of prostoglandins
4) prostaglandins cause vasospasm of the arteries while enzymes digest tissue - eventually blood vessels rupture
What are the stages of the menstrual cycle?
1) follicular phase - first half - dominated by growing follicles that secrete estradiol
2) luteal phase - second half - dominated by corpus luteum that secretes progesterone
3) ovulatory phase is a short period in the middle of the cycle when the LH surge occurs
4) luteal phase is relatively constant due to fixed life span of the corpus luteum
