Reproductive: Steroidogenesis, Folliculogenesis, ovulation Flashcards
Where does LH bind?
theca cells
granulosa cells only during luteal phase
What is the action of LH on theca cells?
produce androstenedione or testosterone which enter the granulosa cells for conversion into estradiol
What is the action of LH during the luteal phase?
binds on granulosa cell to produce progesterone that feeds back into the theca cell for more conversion to androgen
LH is necessary to produce progesterone during the luteal phase. Why is this important?
progesterone is required to maintain pregnancy if fertilization/implantation occurs
Where does FSH bind?
granulosa cells only
What is the action of binding of FSH on granulosa cells?
aromatization of androgens to estradiol;
produce more LH receptors on granulosa cells
What is the importance of estradiol?
released into blood to act locally (increase FSH sensitivity);
systemically to inhibit GnRH secretion
What produces the molecule for negative feedback in female steroidogenesis?
Granulosa cells produce inhibin to inhibit further FSH secretion
When does estradiol not work as a negative feedback inhibitor?
during ovulatory period
Define primordial follicle
immature follicle surrounded by pregranulosa cells ARRESTED IN PROPHASE I OF MEIOSIS until maturation
When does a primordial follicle become a primary follicle?
at puberty during each menstrual cycle
What defines a primary follicle?
oocyte enlarges and granulosa cells mature and proliferate
Granulosa cells aid the primary follicle how?
secrete mucopolysaccharides creating ZONA PELLUCIDA to protect the oocyte and provide nutrients and chemicals for growth
As primary follicle matures, what is added to proceed to a secondary follicle?
granulosa cell layers are added and layer of androgen producing theca cells => THECA INTERNA surround follicle
After the Theca interna is present around the secondary follicle, what occurs?
continues to grow and fibrous theca externa surrounds follicle
Define antrum
follicular cavity that forms from granulosa cell secretions after the fibrous theca externa surrounds follicle
What type of follicle is ready for ovulation?
Graafian follicle (mature)
When does the Graafian follicle resume meiosis? what occurs next?
LH surge to complete 1st Meiotic division => arrested in metaphase of Meiosis 2 prior to ovulation
What is the result of meiosis on the follicle?
produces nonfunctional 1st polar body (degenerates) and larger 2ndary haploid oocyte
What happens if 2ndary haploid oocyte is fertilized?
completes Meiosis 2 to form MATURE OOCYTE and POLAR BODY
What is the first step in ovulation?
antral fluid increases pressure until follicle ruptures and oocyte is extruded
After ovulation, what is the job of the theca and granulosa cells?
theca secretes estrogen;
granulosa secretes progesterone
What is the result of theca and granulosa secretions after ovulation?
produce corpus luteum => new endocrine organ that grows until day 7 after ovulation
If fertilization occurs to corpus luteum, how does it grow?
grows for 3 months via hCG maintenance from embryo until placenta is functional
