Hormonal Control of Reproduction Flashcards
What hormones control the estrous cycle?
- Estrogen
- Follicle stimulating hormone
- Luteinizing Hormone
- Progesterone
- PGF2a
- GnRH
What is the role of the Hypothalamus in the estrous cycle?
- Releases small peptides
- specifically Gonadotropin Releasing Hormone (GnRH)
What does GnRH do?
causes the anterior pituitary to release FSH and LH
What does FSH do?
- Stimulates the maturation of 2° follicles
What does LH do?
- Stimulates maturation of 3° follicles
- stimulates estrogen production
- Stimulates Corpus Luteum production of Progesterone (P4)
What is the importance of eCG (PMSG)?
- Gives both LH and FSH activity (species dependent
What does hCG do?
gives primarily LH activity
What are the functions of GnRH/hCG?
- Causes release of Luteinizing hormone
- Ovulation of luteinization
- Initiates new follicular wave
- Corpus luteum formation
What are the actions of FSH?
- Stimulates growth of follicles in ovaries
- much longer half-life than LH (several hours)
- Can cause single-ovulation species to ovulate several mature oocytes
What are the actions of Prolactin?
- Produced by other tissues besides anterior pituitary
- Prolactin + Estrogen induce lobuloalveolar growth in mammary gland
- Stimulate milk production
- Necessary for CL maintenance in some species
- Involved in maternal behavior
- Hypothalamus releases dopamine which acts to decrease prolactin release
What hormone does the Posterior Pituitary release?
- Oxytocin
- Synthesized by hypothalamus and secreted by nerve endings in posterior pituitary
What does Oxytocin do?
- Stimulates muscle Contraction
- Ejects milk from mammary alveoli
- Increases uterine contractions during parturition
- Establishes maternal behavior
- Facilitates sperm transport (male and female tract)
What are the prescription options for oxytocin?
Pitocin and Oxytocin
What does an ovarian follicle produce? what does it do?
- Estrogen
- acts in a positive feed-back loop with LH
- Estrogen acts on the brain to initiate estrus
What is Folliculogenesis?
What is the function of Theca cells and Granulosa cells?
Produce large amounts of Progesterone
What hormone does the uterus produce? what does it do?
- PGF2a
- produced by non-pregnant endometrium to lyse the CL and initiate the process that leads to ovulation
What are the prescription options for PGF2a?
- Lutalyse
- Estrumate
- and other PGS will lyse a mature CL (diestrus) which causes a rapid decline in Progesterone production by the LC
What happens during luteolysis?
What are induced ovulators?
- Require some stimulation in order to ovulate (e.g. - copulation, genital stimulation)
- Ex: rabbit, cat, camel, ferret
What happens when a queen is stimulated by copulation?
- stimulates LH secretion by the anterior pituitary
- More copulations ⇢ higher LH)
What does the Corpus luteum produce? what does it do?
- Progesterone
- prepares the uterus for the egg
- acts on the brain to override estrogen to prevent estrus behavior
What are prescription options for Progesterone?
- Melengesterol acetate (MGA) and Regu-Mate
- synthetic progestogens
- CIDR insert
- natural progesterone
- Higher lives of Progesterone are need to prevent ovulation than estrus
What doe the Leydig and Sertoli cells produce?
What hormones does the Placenta produce?
- All species - Progesterone, but to different degrees
- Estrogen
- Gonadotropins
- Placental lactogen
- Relaxin
Why does the placenta increase estrogen production in late gestation?
- Prepare uterus for expulsion of fetus
- antagonize progesterone block to uterine contractions
- Stimulate mammary gland development
Why does the placenta produce Gonadotropins?
- Chorionic-origin cells that invade maternal (uterine) tissues
- has LH- and/or FSH-like activity
Why does the Placenta produce lactogen?
- Occurs in primates, ruminants, and rodents
- Similar to prolactin and oxytocin
- Mammary development
- May be involved with CL function
Why does the placenta produce relaxin?
- Relaxes the pelvic ligaments at parturition
- Very high in Guinea pigs - only older sows have risk of dystocia
