12: Menstrual Cycle And Ovulation Flashcards
Where are the two meiotic arrests in oocytes and when they occur?
1st: at prophase 1, during fetal life
2nd: at metaphase II: LH surge, dont progress until fertilization
What is elevated in first and second meiotic arrests?
First: cAMP
Second: MAPK
When are polar bodies 1 and 2 extruded?
Polar body 1: at LH surge/ovulation
Polar body 2: at fertilization
Ovarian reserve
About 300,000 primordial follicles
How many follicles will actually develop and ovulate?
400-500
What induces formation of primary follicles from primordial follicles
FSH
What induces vascularization in secondary follicle formation?
Angiotensin
Histo of theca interna
Looks like it has adipose (clear splotches) bc it forms steroid hormones
What causes increased follicle size once antrum is formed?
Increase of antral size/volume of fluid + proliferation of granulosa cells
What do theca interna and granulosa cells respond to during antral phase of follicle?
Theca interna: responds to LH
Granulosa: FSH
What do theca interna and granulosa synthesize during antral phase of follicle?
Theca interna: androgens
Granulosa: converts thecal cell’s androgens into estrogens
What is induced in granulosa cells in late follicular phase?
LH receptors
When does the oocyte itself grow the most?
Early follicle stages
What hormone sensitivity aids in selection of follicles to continue developing
FSH
How is the dominant follicle chosen in each cycle?
FSH declines, and the largest follicle with the most FSH receptors will become dominant
Follicular atresia
Primary and antral follicles that did not become the dominant follicle -> apoptosis
Theca cells in follicular atresia
Persist and repopulate the stroma of the ovary + retain LH receptors so they can still produce androgens
Hallmark of follicular atresia histo
Glassy membrane due to thick, folded basemement membrane material
HPO Axis reflex
Hypothalamus secretes GnRH -> binds anterior pituitary to secrete FSH and LH -> bind ovaries to produce estrogen, progestin, inhibin, activin
GnRH in a pulsatile rhythm
Causes pulsatile release of LH
Anterior pituitary sensitivity in early follicular phase vs later follicular phase
Early: not very GnRH sensitivite -> only elicit small amounts of LH
Later: become more sensitive -> larger releases of LH
What does LH act on in the follicular phase vs luteal phase
Follicular phase: theca cells
Luteal phase: CL
What determines whether cells respond to activins or inhibins
Where follicles are in different parts of the ovarian cycle
What three hormones cause the LH surge
Estrogen, progestin, activins
Why do LH and FSH rapidly decrease at the start of the luteal phase?
Negative feedback from estradiol, progestin, inhibin
When is basal body temp higher and lower
Follicular phase: high estrogen -> lower BBT
After ovulation: high progesterone -> raises BBT
What happens to basal body temp with regression of CL
Drop in BBT that roughly coincides with onset of next menstruation
What hormone causes higher body temp?
Progesterone
When does estrogen begin to rise in follicular phase?
About 1 week prior to ovulation
Where does the bulk of progesterones come from in the body?
Peripheral conversion from pregnenolone
When is menopause officially started?
12 months after last menstrual period
Hormonal changes that cause menopause
Reduction in estrogen and inhibin -> no negative feedback on LH and FSH -> high LH and FSH
Perimenopause presentation
irregular periods, vaginal and skin dryness, hot flashes, night sweats, sleep disturbances, mood changes, weight gain and slow metabolism, thinning hair, loss of breast fullness
Treatment for menopause symptoms
Mostly to manage S/S and prevent/manage chronic conditions that occur with aging: estrogen therapy, vaginal estrogen, low-dose antidepressants, gabapentin (for hot flashes)
