A&P400 (female reproductive system -- CLASS 3) Flashcards
WHAT ARE THE TWO CYCLE within the female reproductive cycle
1) OVARIAN CYCLE
2) UTERINE CYCLE (menstrual cycle)
1) Ovarian cycle =
Events that occur during & after OOCYTE MATURATION
Focused on the changes in the follicle
—> Follicular phase and luteal phase
what are the phases in the OVARIAN CYCLE
a) follicular phase
b) ovulation
c) luteal phase
2) UTERINE CYCLE (menstrual cycle) =
Changes in endometrium in preparation of fertilized ovum
Regulation of the ovarian AND Uterine cycles
how regulated?
controlled by cyclical changes in hormones
All coordinated by GnRH from the hypothalamus
are two cycles (ovarian and uterine) interdependent?
YES
The two cycles must operate synchronously for proper reproductive function
The regulation of the ovarian (AND UTERINE) cycle(s) begins with …
1) Begins with the release of gonadotropin-releasing hormone (GnRH)
where is GnRH released from?
From hypothalamus
what does GnRH cause?
Causes production and secretion of FSH
Causes production (not secretion) of LH
Cyclical rise in GnRH creates (OVARIAN) cycle
DAY 0 of ovarian cycle
= GnRH levels begin to rise
DAY 0 to DAY 14 (FOLLICULAR PHASE)
= GnRH levels rise steadily until just before day 14
—> GnRH causes LH/FSH levels to rise SUDDENLY (as opposed to gradual rise of GnRH)
after DAY 14, till DAY 28 (LUTEAL PHASE)
= GnRH levels gradually begin to decrease to levels at day 0
= LH & FSH sharp DECLINE shortly after sharp rise.
—-> LH/FSH back to previous decreased levels shortly after day 14
LH levels
in FOLLICULAR PHASE (day 0-14)
—-> LH levels are slightly above base level
—-> they gradually reduce (as tertiary follicles develop, FSH levels decline as a result of negative feedback effects of INHIBIN)
2) Follicular phase of the ovarian cycle
TERTIARY FOLLICLES are formed via FSH stimulation
(Follicular phase begins when FSH stimulates some follicles to become TERTIARY FOLLICLES)
how do FSH levels decline? (around day 14)
As (TERTIARY) follicles develop, FSH levels decline
What causes FSH to decline?
INHIBIN
(as a result of negative feedback effects of INHIBIN)
what do developing follicles secrete?
ESTROGENS
How is LH secretion regulated?
LOW LEVELS of estrogens INHIBIT LH SECRETION
Inhibition DECREASES as estrogen levels climb (released by developing follicles)
I.e.
ESTROGENS INCREASE LH SECRETION
(whereas GnRH is responsible for LH PRODUCTION)
estrogen and basal body temperature
Estrogen decreases basal body temperature about 0.3ºC (0.5ºF) lower than during the LUTEAL PHASE
in which phase does FSH (follicle stimulating hormone) stimulate follicles to become TERTIARY follicles?
FOLLICULAR PHASE
3) OVULATION (OVULATORY PHASE)
GnRH and elevated estrogen levels stimulate LH secretion
Massive surge in LH on or around day 14 triggers:
Completion of meiosis I by the primary oocyte
Forceful rupture of the follicular wall
Ovulation (~9 hours after LH peak)
Formation of CORPUS LUTEUM
when does luteal phase begin?
Luteal phase begins after ovulation
—> AROUND day 14
Mittelschmerz
pain from follicular swelling, ovarian wall rupture, small amount of blood leaking into pelvic cavity surrounding ovulation
4) Luteal phase of ovarian cycle
..
the CORPUS LUTEUM secretes …
PROGESTERONE
Corpus Luteum secretes PROGESTERONE
—> “Stimulates and sustains endometrial development”
as progesterone levels INCREASE, estrogen levels ____, which causes ____.
FALL
—> Suppresses GnRH
What happens if pregnancy does not occur at this stage?
corpus luteum lasts 2 weeks
stops secreting hormones & degenerates into CORPUS ALBICANS
What happens if pregnancy does occur at this stage?
Early cells of the placenta produces hCG (human chorionic gonadotropin)
it rescues corpus luteum to keep it alive & it continues secretory functions
RECAP of events during OVARIAN (& uterine) cycle
1) Release of GnRH
—> leads to production/secretion of FSH @ anterior pituitary
—> leads to PRODUCTION (not secretion) of LH @ anterior pituitary
FSH @ ovary causes
a) ovarian follicle development (tertiary follicle)
b) inhibin secretion (which causes FSH to decline = NEG FEEDBACK)
c) Estrogens secreted (causes LH secretion)
secreted LH causes ____ in ovary
a) Meiosis 1 completion
b) Ovulation
c) Corpus Luteum formation —> which secretes PROGESTERONE (which stimulates ENDOMETRIAL development)
high progesterone —> low estrogen
—> supresses GnRH
NOTE FOLLICLE STAGES DURING OVARIAN CYCLE
recall that FOLLICULAR phase begins when FSH stimulates some follicles to become TERTIARY FOLLICLES
FOLLICULAR PHASE = tertiary follicle development
@ day 14
= OVULATION
(Ovum released)
after day 14 (LUTEAL PHASE)
= corpus luteum formation
—> to mature corpus luteum
—> CORPUS ALBICANS forms if pregnancy DOES NOT occur
IF PREGNANCY DOES* OCCUR, which hormone is formed by which structure
EARLY CELLS OF PLACENTA PRODUCES hCG (human chorionic gonadotropin)
ovarian hormone levels during the ovarian cycle
at day 0
= estrogen > inhibin > progesterone
= all three levels low
towards day 14
= estrogen rises above the other 2
= inhibin also has slight rise (later, just before day 14)
RECALL:
FSH causes estrogen and inhibin to rise
—> inhibin the causes FSH to decline
—> estrogens decline occurs with Progesterone RISE
AFTER DAY 14:
= estrogen levels begin to DECLINE
= progesterone levels RISE with estrogen DECLINE
basal body temperature during ovarian cycle
slightly lower during FOLLICULAR PHASE of Ovarian cycle
small dip @ day 14
then rise slightly high during LUTEAL PHASE
ENDOMETRIAL CHANGES DURING UTERINE CYCLE
.. (will outline after slides on review of hormones)
Follicle Stimulating Hormone (FSH)
Source
ANTERIOR PITUITARY
FSH
Stimulation
GnRH stimulates FSH production/secretion
GnRH released from HYPOTHALAMUS
FSH
Inhibition
inhibin from granulosa cells and corpus luteum, estrogen
—> FSH stimulates INHIBIN, which inhibits FSH
FSH
function
initiates follicle growth
stimulates ovarian follicles to release ESTROGENS and INHIBIN
Luteinizing hormone (LH) is from
source: from Anterior Pituitary
LUTEINIZING hormone promotes formation of corpus LUTEUM
..
LH production is via ____ and secretion is via ____
stimulation: production by GnRH, secretion by ESTROGEN and GnRH
LH inhibition is via
inhibition: INHIBIN from granulosa cells and CORPUS LUTEUM
LH functions
functions:
—> triggers ovulation
—> promotes formation of corpus luteum
—> stimulates corpus luteum to produce ESTROGENS, PROGESTERONE, RELAXIN & INHIBIN
Estrogen is made from ____
cholesterol
estrogen, THREE types
estradiol, estrone, estriol