L4: The Follicular Phase Flashcards
follicle recruitment is stimulated by _____
FSH
what determines follicle selection
follicle with most FSH recceptors
the dominant follicle requires an ______ surge for ovulation
LH
_______ inhibits the LH surge needed for ovulation
progesterone
- high progesterone causes insufficient GnRH/LH levels, inhibiting ovulation
a dominant follicle will become atretic when _____ is high, but will ovulate if ______ decays and _______ decreases
progesterone high –> atretic
corpus luteum decays and progesterone decreases –> ovulation
after luteolysis, the negative feedback of ___________ is removed
progesterone on HPG axis
after luteolysis, positive feedback of ________ occurs
estrogen on HPG axis
formation of ovulatory follicles and estradiol secretion occurs during what phase of estrus
proestrus
phase of estrus characterized by peak estrogen secretion
estrus
phase of estrus when CL forms and begins to secrete progesterone
metestrus
phase of estrus characterized by sustained luteal secretion of preogesterone, CL functions optimally
diestrus
what is Anestrus
period when cyclicity stops (during pregnancy, nursing, migration, stress, malnutrition, disease)
how/why do high levels of progesterone inhibit ovulation
high progesterone causes insufficient GnRH/LH levels
in most animals, ovulation timing corresponds to…?
the events in the estrous cycle
what happens in proestrus
formation of ovulatory follicles & estradiol secretion
when does proestrus happen
begins after CL regression and ends with the onset of estrus
phase of estrous cycle characterized by peak estrogen secretion
estrus
when does estrus occur
after proestrus
what happens during metestrus
CL forms and begins to secrete progesterone
postovulatory phase
what happens during diestrus
sustained luteal secretions of progesterone, optimal CL functioning
average estrous cycle for a bitch
5.5-6.6 months
average estrous cycle for a queen
18 days
average estrous cycle for a cow
21 days
physical signs of proestrus in the bitch
- vulva swollen caused by increasing estrogen
- bloody discharge from uterus
- flirting w/ males
what day of the estrous cycle does proestrus usually occur in the bitch
9 d
what day of the estrous cycle does estrus usually occur in the bitch
9 d
how long is pregnancy in a bitch
63 d
what day of the estrous cycle does proestrus usually occur in the queen
8-10 d
signs that a queen is in proestrus
- attraction to males
- rubbing head and neck on objects
- vocalization
- postuing, rolling
what day of the estrous cycle does estrus usually occur in the queen
9 d
ovulates 27 hours after mating
gestation period in queens
60 d
what day of the estrous cycle does proestrus usually occur in the mare
3 d
what day of the estrous cycle does estrus usually occur in the mare
4-8 d
signs that a mare is in estrus
- tail raised
- squats
- frequent urination
- exposed clitoris
- toleration of copulation
cows that come into estrus in the AM can be bred…
that same afternoon
cows that come into estrus in the afternoon can be bred…
the next AM
how does the negative feedback on the HPG axis change at puberty
negative feedback is reduced, resulting in more GnRH pulses of higher amplitude
GnRH pulses cause the release of LH + FSH
3 periods during which the HPG axis is activated
- fetal development
- ovarian cycles during adulthood
- puberty
During ________, there is a strong negative feedback on the HPG axis
adolescence (pre puberty)
at puberty, the negative feedback on HPG axis is reduced, resulting in more ________pulses of a higher amplitutde
GnRH
GnRH pulses cause the release of ____+_____ and stimulates the gonadal tissue to increase ______ synthesis and secretion
LH + FSH
steroid synthesis
