estrous cycle Flashcards
goal of the reproductive system
-optimize opportunity to become pregnant
- maintain pregnancy
lordosis
- swayback
- posture changes because of heat
estrus
time that female is sexually receptive and in standing heat
estrous cycle
interval from one heat until the next
estrous vs estrus
estrous (adjective) describes the cycle while estrus (noun) is standing heat
what are the four stages to the estrous cycle
estrus
metestrus
diestrus
proestrus
steps to estrus
- high estradiol causes GnRH surge
- LH surge
- ovulation
what is metestrus
ovulation to functioning CL
what occurs in metestrus
- hormone levels low
- progesterone level starts to increase
how long does metestrus last
1-5 days
- quick process
in what stage is the CL fully functional
Diestrus
What occurs in diestrus
- high levels of progesterone
- embryo develops in uterus
if embryo develops in uterus during diestrus what occurs
no PGF2a being released from uterus so no luteolysis
if no embryo in uterus what occurs
PGF2a causes CL to regress (luteolysis occurs)
when luteolysis occurs, what happens to progesterone and inhibition
progesterone decreases
inhibition removed
what has to happen for no follicle recruitment to occur
low levels of GnRH
low levels of LH and FSH
how does the next generation of antral follicles become recruited
- progesterone levels decrease
- negative feedback to hypothalamus decreases
- GnRH levels increase
when is the CL undergoing regression, or luteolysis
proestrus
in what stage does the antral follicle develop
proestrus
what occurs during proestrus
- progesterone levels fall
- switch from progesterone dominance to estradiol dominance
- female starts to become recpetive
what does estradiol help with
preparing the uterus and oviducts for sperm transport and fertilization
the estrous cycle is divided into how many phases and what are they
- follicular phase
- luteal phase
what is the follicular phase
- begins with Cl regression
- ends with ovulation of mature dominant and ovulatory follicles
what is the predominant hormone used in the follicular phase
estradiol
what are the two substages of follicular phase
- proestrus- CL regression to heat
- estrus- sexual receptivity
what is the luteal phase
formation of the CL after ovulation until CL regresses
in what phase is the CL most functional
luteal
what is the main hormone for the luteal phase
progesterone
what are the substages of luteal phase
- metestrus- transition period following ovulation until CL functional
- diestrus- CL is functional and longest stage
