Lecture 06: Female Reproductive Cycle (Kelleman) Flashcards
estrous cycle
reproductive cycle of non-primate species. Period from one estrus to the next.
2 phases of estrous cycle
follicular and luteal
estrous vs. estrus
estrous refers to the cycle, estrus refers to period of behavioral receptivity during the estrous cycle
Monoestrous and species
one estrous cycle per year. Wolves, foxes, bears, most dogs
polyestrous and species
repeated estrous cycles are uniformly distributed throughout the year. Cattle, swine, rodents
seasonally polyestrous and species
repeated estrous cycles for a PORTION of the year. Horses, sheep, goats, cats
anestrus
any time period when the female is not cycling
cyclicity of seasonal breeders is determined by which environmental factors? What hormone do these factors directly influence?
photoperiod and temperature. Regulates melatonin secretion
More melatonin is produced in darkness or light?
darkness!
what produces melatonin?
pineal gland. It is an indoleamin hormone
Short-day breeders and species
cyclicity occurs during fall months, give birth in spring. Sheep, goats
melatonin stimulates or inhibits GnRH secretion in short day breeders? **
stimulates
Long-day breeders and species
cycle in spring/summer and give birth in spring. Horses
melatonin stimulates or inhibits GnRH secretion in long day breeders? ***
inhibits
What does melatonin act on?
hypothalamus
What hormone does hypothalamus release (in reference to cyclicity)?
GnRH
What does GnRH act on?
pituitary gland
What hormones are released by pituitary gland (in reference to cyclicity)
FSH, LH
What do FSH and LH act on?
gonads
What is reproductive cyclicity driven by?
secretion of hypothalamic and pituitary hormones
How is progesterone used clinically?
used to make fake CL and keep animal out of heat
Prostaglandin fx
luteolysis (killing off CL)
FSH, LH, and inhibin are included in which class of hormones?
glycoproteins
GnRH function
(released by hypothalamus) stimulates synthesis and secretion of LH and FSH from anterior pituitary gland
FSH fx
(released from AP) promotes follicular development in the female.
LH fx
(released from AP) causes final follicular maturation and ovulation. Promotes development and maintenance of CL
What hormones inhibit FSH?
Inhibin, estrogen
What hormone inhibits LH?
Progesterone
Where is estrogen produced? Fx?
Produced in ovarian follicles.
- Causes estrous behavior, ONLY when progesterone is low.
- Inhibits FSH
- High lvls cause GnRH and LH surge
Where is progesterone produced? Fx?
Corpus luteum
- Pregnancy maintenance
- Inhibits estrous behavior
- Inhibits GnRH, LH
Where is prostaglandin produced? Fx?
Endometrium
-Causes destruction of CL
Decreasing Prostaglandin –> GnRH
increases
Which estrous phase has high progesterone?
luteal phase
Which estrous phase has high estrogen?
follicular phase
In which phase of estrous cycle does ovulation occur?
follicular phase
2 subdivisions of follicular phase
Proestrus and estrus
2 subdivisions of luteal phase
metestrus and diestrus
Main events of proestrus
1) declining progesterone, rising estrogen
2) 3rd wave of follicles recruited, dominant follicle selected but doesn’t ovulate yet
3) female attracts male but doesn’t allow mating
Main events of estrus
1) high estrogen, low progesterone
2) ovulation of dominant follicle occurs
3) female receptive and mating occurs
Main events of metestrus
1) declining estrogen, rising progesterone
2) CL forming
3) female not receptive
4) 1st wave of new follicles recruited, but does not reach ovulation because of high progesterone
Main events of diestrus
1) High progesterone, low estrogen
2) 2nd wave of follicles recruited, ovulation not reached because of high progesterone
3) female refuses male
luteolysis and when it occurs
when no pregnancy, prostaglandin released by endometrium and CL destroyed. Occurs at end of diestrus
Order of estrous cycle phases
Proestrus –> estrus –> metestrus –> diestrus “PEMD”
How do rising lvls of estrogen feed back to surge center of hypothalamus? ***
Positive feedback loop. Estrogen –> GnRH –> LH –> ovulation and spinofollicular maturation
How does inhibin released by dominant follicle feed back to hypothalamus?
negative feedback loop. Inhibits FSH
