Female Reproductive Anatomy & Physiology Flashcards
What are the major components of the hypothalamic-pituitary-gonadal axis?
- GnRH is produced by the hypothalamus
- hypothalamus induces the production of LH/FSH in the anterior pituitary
- LH/FSH act on the ovaries and gonads to produce their respective hormones (estrogen, progesterone, testosterone), which can act as negative feedback and block GnRH production
- kisspeptin can be activated by estrogen to further induce GnRH secretion
What sex hormones are produced in the 2 anatomical sites of the pituitary?
ANTERIOR = FSH, LH
POSTERIOR = oxytocin (stored)
What is the source of GnRH? What is its target? What is the female response?
hypothalamic surge and tonic centers
anterior pituitary
release of FSH and LH
What is the source of FSH? What is its target? What is the female response?
anterior pituitary
ovary granulosa cells
follicular development and estradiol release
What is the source of LH? What is its target? What is the female response?
anterior pituitary
ovary theca internal and luteal cells
- ovulation
- forms corpus luteum
- progesterone release
What is the source of prolactin? What is its target? What is the female response?
anterior pituitary
mammary glands
- lactation
- maternal behavior
- supports CL in the bitch
What is the source of oxytocin? What is its target? What is the female response?
made in hypothalamus, stored in posterior pituitary, and synthesized by CL
myometrium, endometrium, mammary glands
- uterine contractions
- uterine secretion of PGF2alpha
- milk ejection
What is the source of estradiol? What is its target? What is the female response?
granulosa cells of the follicle, placenta
hypothalamus, mammary glands, reproductive tract
- sexual behavior
- secretion of GnRH
- uterine motility
- mucous secretion
What is the source of progesterone? What is its target? What is the female response?
CL and placenta
endo/myometrium, mammary glands, hypothalamus
- inhibits GnRH and reproductive behavior
- promotes pregnancy
What is the source of testosterone? What is its target? What is the female response?
theca internal cells
brain, granulosa cells, skeletal muscle
- estradiol synthesis
- abnormal masculinization
What is the source of inhibin/activin? What is its target? What is the female response?
granulosa cells
anterior pituitary
- INHIBIT = inhibits FSH secretion
- ACTIVIN = stimulates FSH secretion
What is the source of PGF2-alpha? What is its target? What is the female response?
uterine endometrium
CL, myometrium, follicles
- luteolysis
- uterine contraction
- ovulation
What is the source of PGE2? What is its target? What is the female response?
ovary, uterus, embryo
CL, oviduct
- ovulation
- progesterone release from CL
What is the source of human chorionic gonadotropin (hCG)? What is its target? What is the female response?
trophoblast of blastocyst
ovary
production of progesterone by ovary to prepare for pregnancy
What is the source of equine chorionic gonadotropin (eCG)? What is its target? What is the female response?
chorionic girdle cells, endometrial cups
ovary
formation of accessory CLs
What is the source of lactogen? What is its target? What is the female response?
placenta
mammary glands
mammary stimulation
What are the 2 major relevant functions of GnRH (analogs) in veterinary medicine?
- induce cyclicity and ovulation
- treat follicular cysts
What are the 2 major functions of iatrogenic oxytocin?
- induced smooth muscle contractions
- social, maternal, bonding behavior (receptors in brain)
What is the main clinical relevance of using oxytocin? How is it specifically used in mares?
- induced milk ejection
- induces myometrial contractions during parturition and to promote uterine clearance during estrus
induces parturition
Anatomy of the female reproductive tract:
What are ovarian follicles? How do they compare in horses?
structures in the ovary that contain the oocyte and must rupture for release into the oviduct for fertilization
all oocytes are released at one site after they are erupted internally, making follicles unable to be palpated on rectal exams
What are the 4 types of uteruses seen in mammals?
- simplex = no uterine horns (primates)
- duplex = two cervices (marsupials, rabbit)
- bicornuate with highly developed uterine horns =(bitch, queen, sow)
- bicornuate with poorly to moderately developed uterine horns = (mare, cow)
What are the 2 major requirements for reaching puberty? Why are they commonly breed-dependent?
GnRH neuronal development requires
- threshold body size
- exposure to environment or social cues - photoperiod, presence of males, density of group housing, stress
smaller breeds reach threshold body size earlier - Chihuahua will reach sexual maturity before Great Danes
What are 3 possible influences of metabolic signals on GnRH neurons?
- BLOOD FATTY ACIDS (indicator of nutritional status) may stimulate neurons that lead to GnRH neuron stimulation
- BLOOD GLUCOSE (indicator of metabolic status) may stimulate neurons that are able to stimulate GnRH neurons
- LEPTIN is secreted by adipocytes and stimulates neutopeptide Y neurons anf GnRH neurons
(all stimulate kisspeptin neurons!)
How do hormone levels compare before and during puberty?
BEFORE = tonic center has a high sensitivity to negative feedback from estradiol - low estradiol = low GnRH = low FSH/LH = low estradiol
DURING = tonic center negative feedback decreases - low estradiol = more GnRH = high FSH/LH = more estradiol to tonic and surge centers = preovulatory LH surge = ovulation
What are the 3 types of estrous cycles?
- nonseasonally polyestrous - cows, sows, alpacas, llamas
- seasonally polyestrous - long day breeders (mares, queens), short day breeders (small ruminants)
- monoestrous - bitches (long anestrus)
What are the 4 stages of the estrous cycle?
- proestrus
- estrus
- diestrus
- anestrus - no ovary activity
What are the 2 substages of estrus?
- metestrus - early diestrus with increased progesterone to allow follicle to rupture into the corpus hemorrhagicum
- postestrus - induced ovulators, no CL development and no signs of estrus
What are 5 causes of anestrus?
- species - anestrus long in bitches
- pregnancy, lactation - no need to go though estrous cycle
- stress, nutrition - lean = likely to have an altered and longer anestrus to save energy
- pathology
- season - mares and small ruminants
What are the 2 types of seasonally polyestrous animals? What is responsible for the difference?
- long day breeders - mares
- short day breeders - small ruminants
- long photoperiods induce the pineal gland to have a low melatonin release
- short-day kiss neurons are inhibited, leading to decreased GnRH, FSH, and LH, resulting in no cycles
- long-day kiss neurons are stimulates, leading to increased GnRH, FSH, and LH, resulting in cyclicity
What are the 2 phases of the estrous cycle?
- follicular phase - proestrus and estrus, where the follicles are growing in response to high estradiol
- luteal phase - diestrus, where the CL is growing in response to high progesterone
How does the follicular phase occur?
- decreased progesterone from CL
- increased GnRH
- increased FSH and LH
- this leads to proestrual follicular development
- resulting inhibin increase causes a decrease in FSH to block the growth of other smaller follicles
- resulting to estradiol increase causes a preovulatory LH surge
What additional event also occurs during the luteal phase?
folliculogenesis
Estrous cycle:
What are the 4 steps of folliculogenesis? What hormones are responsible for each?
- RECRUITMENT - high FSH, low LH, low inhibin and estradiol
- SELECTION - low FSH, moderate LH, low inhibin, high estradiol
- DOMINANCE - low FSH, high LH, high inhibin and estradiol
- ATRESIA
Folliculogenesis:
active CL from previous cycle produce progesterone, which keeps dominant follicles from emerging
as CL regresses, progesterone decreases, and ovulation occurs
How does the dominant follicle emerge? How do the levels of FSH and LH also take part?
secrete inhibin and estradiol to inhibit other follicles
- LOW FSH = atresia of other follicles
- HIGH LH = ovulation
What is the two-cell-two-gonadotropin theory?
- LH binds to theca internal resulting in cholesterol to be converted into testosterone, which enters the granulosal cells
- FSH binds to granulosa cells to convert the testosterone from estradiol
What are some signs of estrus?
- increased mucosal thickness
- increased mucous production
- increased blood flow and leakage
- leukocytosis
- edema
- increased muscular tone (not in mares!)
- lordosis
- increased phonation and physical activity
What are some spontaneous and induced ovulator species?
SPONTANEOUS - horse, cow, sheep, goats, pigs, dogs
INDUCED - cats (multiple copulations needed), rabbits, ferrets, camelids (one copulation enough)
How does induced ovulation work?
- nerve endings in the vagina sense copulation
- nerve impulses run to the spinal cord to the hypothalamic tonic center, leading to a release in GnRH
- LH surge results
What type of process is ovulation? What 5 things occur?
inflammatory
- vasodilation
- hyperemia
- edema
- collagenolysis
- cell proliferation
What occurs during the luteal phase of the estrous cycle?
corpus luteum forms due to elevated progesterone levels
What happens during diestrus?
progesterone levels increase to prepare for pregnancy and inhibit reproductive behavior
What are the 4 effects of diestrus?
- reduced uterine tone
- decreased uterine resistance to infection (male hygiene important!)
- secretion of histotroph (uterine milk) in preparation for implantation of embryo
- stimulation of mammary glands
What causes luteolysis? What 3 things does this result in?
PGF2 alpha
- decreased CL blood flow
- inhibits progesterone synthesis
- induces apoptosis
What does the PGF2 alpha responsible for luteolysis come from?
comes from the endometrium to the follicles due to vascular counter current exchange
