Reproduction 3: Female Repro/Menstrual Cycle Flashcards
What is the fundamental reproductive unit of the female repro system?
Gonad = ovary, follicle is the primary reproductive unit
What is included in the female reproductive system?
oviducts, uterus, cervix, vagina, external genitalia
What is the internal genitalia derived from
mullerian ducts
GnRH is activated at puberty. What activates it?
Kisspeptin
What promotes secondary sex characteristics?
increased GnRH pulsatility during REM sleep
What stimulates pulsatile release of gonadotropins?
GnRH
What is the differential levels of GnRH at different stages of life?
spikes in fetal and infant development
low during childhood
elevated at night during puberty
elevated spikes during reproductive years
constantly high in menopause due to lack of neg feedback
The menstrual cycle causes physiological changes in what two organs?
ovary and uterus
What are the cycles called for the ovary and uterus respectively?
ovary: ovarian cycle
uterus: endometrial cycle
What causes the monthly menstrual pattern?
HPG axis feedback
Discuss the female HPG Axis
hypothalamus releases GnRH
GnRH stimulates anterior pituitary to release LH and FSH
What does FSH target?
Granulosa cells
What does LH target?
Theca cells and granulosa cells
What do theca cells do?
produce progestins and androgens
What do granulosa cells do?
produce progestins, estrogens, inhibins, and activins
converts androgen precursors to estradiol
What does FSH do?
stimulates follicular development and conversion of androgen precursors to estradiol
What does LH do?
stimulates biosynthesis of estrogens, induces ovulation and luteinization
When is LH higher than FSH?
reproductive years
What do theca cell do and what kind of receptors do they have?
produce androgens and progestin
receptors for LH
What do granulosa cells do and what kind of receptors do they have?
produce estrogens, progestins, inhibins, activins
receptors for LH and FSH
What kind of feedback do estrogens have?
negative and positive!
positive important for ovulation
What are the three phases of the ovarian cycle?
Follicular phase
Ovulatory phase
Luteal phase
What happens in the follicular phase?
Growth of dominant follicle
What happens in the ovulatory phase?
Follicle rupture and release of oocyte
What happens in the luteal phase?
Formation of corpus luteum
What are the three phases of the endometrial (uterine) phase
Menstrual phase
Proliferative phase
Secretory phase
What do HPG hormones do?
drive coordinated physiological changes during the menstrual cycle
What do physiological changes do?
Signal the hypothalamus
When does the proliferative phase occur?
coincident with majority of follicular phase of ovary
When does the secretory phase occur?
coincident with luteal phase of ovary
What occurs during the menstrual phase?
Endometrial shedding
coincident with early follicular phase of ovary
How long is the follicular phase?
variable, 10-14 days
How long is the ovulatory phase?
1-3 days
How long is the luteal phase?
14 days
Describe the stages of a follicle as it passes through the ovarian cycle
primordial follicle -> primary follicle -> secondary follicle -> mature (Graafian) follicle -> (ovulation/follicular rupture) -> corpora lutea -> corpus albicans -> atretic follicle
How do the L and R ovaries coordinate?
Alternate between ovaries every month/cycle. If both go through the cycle at the same time you can get dizygotic twins
When do the number of primordial follicles peak? How many are left at puberty?
Peak at 20 wks gestation. Only 10% left at puberty
What is a follicle?
one oocyte surrounded by a cluster of granulosa cells (germ cell surrounded by endocrine cells)
What does the mature ovary do?
maintain and nurture resident oocyte
mature oocyte and release it at the appropriate time
prepare vagina and fallopian tubes for fertilization
prepare the uterine lining to accept and implant a zygote
maintain hormonal support for the fetus until the endometrium is ready to do so
In the ovarian cycle, what does day 1 signify?
the first day of menses
What is a primordial follicle?
outer layer of pregranulosa cells plus a small oocyte
What stage are oocytes arrested in?
diplotene stage of prophase
What is a primary follicle?
Larger oocyte surrounded by cuboidal granulosa cells
What is required for the follicle to progress from the primordial to primary stage, and where does this happen?
Requires FSH, can happen in utero
What happens in a secondary follicle?
differentiation of stromal cells into theca cells
increased number of granulosa cells that become multilayered
enlargement of oocyte
What happens in a tertiary follicle, and what else is it called?
Early antral follicle
granulosa cells secrete fluid and create antrum
Granulosa cells closest to oocyte secrete
mucopolysaccharides – forms zona pellucida
How long does it take to mature from a primary to a mature graafian follicle?
10-14 days
What is the selection of a dominant follicle based on?
sensitivity to FSH and local paracrine actions of AMH produced by granulosa cells
What iss a graafian follicle?
the dominant follicle
What 3 types do granulosa cells stratify to?
mural cells
cumulus
antral
What do mural cells do?
farthest from oocyte
highest number of LH receptors
most metabolically active
What are the cumulus cells?
near oocyte, shed at ovulation
What are the antral cells?
face antrum, become luteal cells at ovulation