Physio of the Estrous Cycle Flashcards
Who is involved in the endocrine regulation of the estrous cycle?
Hypothalamus: GnRH
Hypophysis: FSH and LH
Ovaries: estradiol, progesterone, inhibin
Uterus: Prostaglandin PF2a
What role does inhibin play in the estrous cycle?
Prevents the development of multiple follicles during ovulation. Only one follicle should ovulate.
What is the follicle producing from the primary stage to the Graffian stage?
Estradiol
What is the follicle producing after the Graffian stage (CH and CL)?
Progesterone
Where in the ovaries are follicles found?
Cortex
If ovulation without fertilization occurs, the uterus produces _____ to lyse the corpus luteum and begin another cycle.
Prostaglandin PGF2a
What are the committed follicles?
Follicles from the resting pool that are activated to begin growing
When is development of the follicle gonadotropin (FSH and LH) independent?
Up to the formation of the antrum.
- Independent: primordial, primary, secondary
- Responsive: preantral, antral
Gonadotropin dependent stages of follicle development
Antral, Graffian, up until ovulation
At what stage is the follicle most susceptible to atresia?
Preantral to early antral transition, during formation of the theca cell layer
Features of the corpus hemorrhagicum
Immediately after ovulation
Antrum collapses
Low progesterone levels
*will see bloody discharge in cows
Features of the corpus luteum
Theca interna and granulosa cells proliferate and differentiate into small and large luteal cells.
Progesterone levels increase
Large luteal cells also secrete oxytocin and relaxin
Area of the brain responsible for regular pulses of GnRH
Tonic GnRH Center of the hypothalamus.
*affected by internal and external (melatonin) signals
Area of the brain responsible for releasing bursts of GnRH to initiate ovulation.
Surge Center of the hypothalamus
- female brain only!
- w/out sufficient GnRH burst, surge of LH is not released and ovulation doesn’t occur
Effects of estrogen during ovulation
Thickening vaginal mucosa Mucus secretion Epithelial mitosis (endometrium) Increased secretory and ciliary beat activity Endometrial edema Myometrial activity Estrous behavior