Cycles Flashcards
What are the two main phases?
follicular, luteal
What 2 phases can follicular be split into?
proestrus, estrus
What 2 phases can luteal be split into?
metestrus, diestrus
What is the difference between estrus and estrous?
estrus describes sexual receptivity (“heat”), estrous describes the cycle
What happens during proestrus? How long is it?
Drop in progesterone due to luteolysis, increase in FSH and LH and estradiol due to follicular maturation
2-5 days
What happens during estrus?
peak estradiol follicles due to dominant follicle
peak FSH, LH
ovulation
What happens during metestrus?
follows ovulation
ovulated follicle undergoing luteinization to CL
LH, FSH, estradiol, progesterone low (P increase at end)
What happens during diestrus?
high circulating progesterone is dominant
LH, FSH, estradiol low
important to support uterine endometrium for pregnancy
terminated with luteolysis
What are follicular waves?
multiple waves of follicular development that never reach completion because of inadequate hormone signals
What are the 3 phases of follicular development?
recruitment, selection, dominance
What happens during the recruitment stage of folliculogeneis?
entrance of cohort of antral follicles into gonadotropin-dependent stage
What happens during the selection stage of folliculogenesis?
reduction in number of recruited follicles to 1 follicle (or number of follicles that normally ovulate in that species)
What happens during the dominance stage of folliculogenesis?
inhibition of further recruitment and development of other follicles, this one grows to be ovulated or becomes atretic due to wrong stage
What is atresia?
follicle degeneration
What is spontaneous ovulation?
ovulate regularly after end of each follicular cycle
induced by ovarian steroids and gonadotropins
humans, sheep, cattle
What is induced ovulation?
go through follicular phase but ovulation occurs only after mating
neural stimulation due to mating causes a reflex release of LH
cats, rabbits, ferrets
What are the steps of estrous synchronization?
suppression of HPG, restarting the cycle, advancing estrous
What happens during suppression of HPG during estrous synchronization?
mimicking the presence of CL with progesterone (progestins)
progestins (MGA, CIDR) prevent LH surge and ovulation, suppresses uterine activity
What is CIDR?
progestin
vaginal implant that secretes progesterone through vaginal wall lining
What is MGA (melengestral acetate)?
progestin
feed supplement that binds progesterone receptors
What happens during cycle restarting in estrus synchronization?
prostaglandin PGF2a
kill the CL so that estrus will occur 2-5d after
What happens during advancing estrus during estrus synchronization?
GnRH
ovulates dominant follicles greater than 10mm
ovulation occurs 24-33h after
