Unit 7 - Female Reproductive Endocrinology Flashcards
phases of the ovarian cycle
series of hormone-mediated changes in ovaries culminating in monthly production of viable ovum in women of reproductive age
- follicular - FSH stimulates development of follicles; rising estradiol
- ovulatory - LH surge causes rupture of mature Graafian follicle and oocyte discharge (mid-cycle)
- luteal - LH converts ruptured vollicle into corpus luteum; high progesterone plus some estradiol
2 functions of ovaries
- produce/release ova
- produce hormones
when does degeneration of corpus luteum into corpus albicans proceed?
if fertilization doesn’t occur (low estrogen and progesterone)
what is the most important estrogen?
beta-estradiol
what happens to the ovary as one progresses from pre-puberty to after puberty?
before: ovary has many primordial follicles that stay dormant
after: several follicles ripen each menstrual cycle, but only 1 matures (the others regress)
- after ovulation and ovum release, the mature follicle involutes to corpus luteum, which stays to the end of the cycle
maturation of ovarian follicle
primordial follicle - 30-60 um in diameter, and production from primary oocytes is complete by 6 mo of age
primary follicles - develop during monthly ovarian cycle to secondary –> early tertiary follicle
graafian follicle - attains diameter of 20-33 mm
what is the antrum of a follicle?
in early tertiary and graafian follicles
- fluid filled cavity that sustains the follicle
- has very high [hormone]
where are thecal cells on follicles?
the outside; good vascularization
how does the ovarian cycle coincide with the endometrial cycle?
follicular phase = proliferative phase (varies, ~11 days)
luteal phase = secretory phase (FIXED AT 14 DAYS)
corpus luteum regression = menstrual phase (usually divided between follicular and luteal phases)
endometrial cycle phases
- proliferative - thickness of endometrium increases from 1-2 mm to 8-10 mm
- dominated by estrogens and variable in length - secretory - dominated by progesterone with fixed length of 14 days following ovulation
- progesterone promotes accumulation of glycogen, increased glandular secretions, and increased vascularity - menstrual - prostaglandin-mediated vasoconstriction of spinal arteries and local ischemic injury/inflammation
- regression of corpus luteum
how do coordinated hormonal secretions prepare uterus?
- estradiol (follicular phase) promotes proliferation of endometrium and “primes” uterus for progesterone actions by increasing progesterone receptors
- progesterone (luteal phase) converts proliferative uterus to secretory uterus (enhance differentiation of epithelial and stromal cells, promoting glycogen storage and secretion of CHO-rich mucus)
late follicular and ovulatory phases feedback
GnRH (from hypothalamus) –> pituitary –> LH/FSH
- LH –> thecal cells (make androgens) and granulosa cells (make estrogens and activins)
- FSH, androgens –> granulosa cells only
- estrogens –> pituitary and hypothalamus via positive feedback
- activins –> acts on AP only
luteal phase feedback
same as usual, but this time theca cells make progestins and androgens, and granulosa cells (corpus luteum) make progestins, estrogens, and inhibins
- progestins and estrogens feedback negatively on pituitary and hypothalamus
- inhibin works only on FSH on AP
how are GnRH and LH “pulsatile”?
pulsatile release of GnRH in both early and late follicular phases causes LH rises (“surge” in late)
-high circulating estrogens in LFP “sensitize” AP gonadotrophs to GnRH stimulation to cause the “surge” in LH (and less importantly FSH) release necessary for rupture of growing follicle and ovulation
what happens to androgens from theca cells that are transferred to granulosa cells?
androgens are converted to estrogens in granulosa cells
