Reproduction 3 Flashcards
What is the fundamental reproductive unit in the female?
follicle
What is the female gonad?
ovary
Describe the anatomy of the female reproductive tract.
Reproductive tract =
oviducts, uterus, cervix, vagina, external genitalia
upper 1/3 of vagina, through uterus and oviducts is considered internal genitalia- these are structures derived from Mull. ducts
How is it that someone could lack female internal genitalia but have external female genitalia?
lower 2/3 of vagina, all external genitalia. those developmental processes controlled diff. this is why we see vagina could end in blind pouch w no internal genitalia (external structures go along default pathway)
male Pseudohermaprhoditism (46 XY loss of X linked AR gene Y chromosome – induces mullerian duct regression, testes (undescended); lack of androgen effects (no Wolffian duct development, no external genitalia)
Describe the female pubertal activation of HPG axis.
(focus on GnRH)
childhood
puberty
reproductive years
menopause
Slide 8
GnRH activated at puberty by Kisspeptin in the hypothalamus
Increased GnRH pulsatility during REM sleep promotes secondary sex characteristics
GnRH stimulates pulsatile release of gonadotropins
in childhood GnRH turned off (no activity, no pulsatility, quiescent state) Kisspeptin will activate GnRH at puberty.
reprod. years its consistent. day and night no pulsatile change. only during puberty
metapause its elevated levels of GnRH across board (lack of neg. feedback occurring)
gonadotropins … lots of gonadotropin surges in fetus before birth, driving development
What is the difference between the menstrual rhythm and menstrual cycle?
HPG axis feedback mechanisms generate a cyclical monthly pattern of hormone secretion called the “Menstrual Rhythm”
The menstrual cycle consists of physiological changes in 2 organs: ovary and uterus.
Ovary = ovarian cycle
Uterus = endometrial cycle
How do ratios of LH: FSH change across female lifespan?
gestation, childhood, reproductive period, menopause/senescence
childhood- FSH more than LH
reprod. LH more than FSH
senescence FSH more than LH
FSH- early FSH imp. for initial development of follicles that happens in gestation.
What are the two cell types in ovary? What receptors are present? Describe their action.
OVARY:
THECA CELLS –
Produce androgens and progestins
Have LH receptors
GRANULOSA CELLS –
Produce estrogens, progestings, inhibins, activins
Have both LH and FSH receptors
There is negative AND positive feedback actions of estrogens. When does positive feedback occur?
positive feedback ONLY happens at time of ovulation.
Positive feedback important for ovulation
When is day 1 of the cycle?
DAY 1 = FIRST DAY OF MENSES
Describe the menstrual cycle. Ovarian and Endometrial. Describe the phases. Include approx time length.
What drives these physiological changes? What structure is signaled by these changes?
OVARIAN CYCLE – 3 PHASES (OVARY)
Follicular phase = growth of dominant follicle (10-14 days)
Ovulatory phase = follicle rupture and release of oocyte (1-3 days)
Luteal phase = formation of corpus luteum (14 days)
ENDOMETRIAL CYCLE – 3 PHASES (UTERUS)
Menstrual phase
Proliferative phase
Secretory phase
HPG AXIS HORMONES DRIVE COORDINATED PHYSIOLOGICAL CHANGES DURING THE MENSTRUAL CYCLE. PHYSIOLOGICAL CHANGES SIGNAL HYPOTHALAMUS
What is a Graafian follicle?
this is the mature/dominant follicle.
When do primordial follicles reach their peak?
How many are left at puberty?
Primordial follicles reach peak at 20 weeks gestation. Only 10% remaining at puberty.
primary oocyte, that has been arrested in diplotine stage of meiosis, surrounded by follicular cells. at time of birth (peak follicle at 20 weeks) have lost lots of primordial follicles, and by puberty only have 300,000 primordial follicles left (from starting w 7 mill. follicles), most die and undergo atresia before go any further maturation beyond primordial follicle …have about a tenth remaining that will grow and become primary, secondary, tertiary … 30, 000 will maybe grow, and 30,000 won’t go further
only 450 become dominant follicles during female reprod. lifetime
slide 17
Describe primordial and primary follicles. What stimulates primordial to primary stage?
Primordial follicles: outer layer of pregranulosa cells + small oocyte
*oocytes are arrested in diplotene stage of prophase (meiosis I); no thecal cells
Primary follicles: larger oocyte surrounded by cuboidal granulosa cells
Require FSH stimulation to develop from primordial to primary stage… has to happen at time of puberty (when start getting increased levels of gonadotropins). Can happen in utero bc of spikes you see of FSH during infancy. some primary follicles at birth as well
Describe secondary follicles. (How differ from primary? )
Secondary follicles:
Differentiation of stromal cells to Theca cells
Increased numbers of granulosa cells that become multilayered
Enlargement of oocyte
What are pre-antral follicles?
Note: primary and secondary follicles are also called “pre-antral” follicles
if does not have antrum- call pre-antral…and can be primary and secondary state
Describe the tertiary follicle.
Early antral follicle = tertiary follicle
Granulosa cells secrete fluid and create antrum
Granulosa cells closest to oocyte secrete mucopolysaccharides – forms zona pellucida
protective coating around oocyte that the sperm will have to penetrate through and this is why sperm needs hydrolytic enzymes in cap to penetrate through z. pellu. to get to oocyte.
*several antral follicles are “recruited” at the end of each ovarian cycle to become the next dominant follicle.
14 days to get to this point.
How long does maturation from primary to Graafian follicle take?
How is it determined which becomes the dominant follicle?
10-14 days maturation from primary to dominant
The initial cohort of follicles that started maturing will all undergo atresia except 1 (usually).
Dominant follicle is based on sensitivity to FSH and local paracrine actions of AMH (produced by granulosa cells) AMH prod. by gran. cells. secrete in paracrine way to cause other follicles nearby to undergo atresia.
which becomes dominant dep. on FSH receptors and how sensitive a follicle is to FSH. the more FSH receptors a follicle has, the more sensitive to FSH and that will become the dominant follicle and the rest will die.
Granulosa cells stratify to 3 types:
Which type will form luteal cells after ovulation? Which are most metabolically active? Which are shed at ovulation? Which are farthest from oocyte? nearest to ooycte?
Mural = farthest from oocyte. Lots of LH receptors; most metabolically active
Cumulus = near oocyte; shed at ovulation
Antral = face antrum; forms luteal cells after ovulation
gran. cells have both LH and FSH receptors.
Mural has most LH receptors ( all 3 types have lots of FSH receptors)
once oocyte released- cumulus cells go w the oocyte but Ant. remain behind and help to form the corpus lut.
