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APBI 312 > Estrous Cycle > Flashcards

Estrous Cycle Flashcards

1
Q

estrous cycle (4)

A
  • the period between two estrous/ovulation episodes
  • ovarian cycle with regular duration
  • variable among species, breeds, and individuals
  • can be affected by multiple factors or pharmaceutically controlled with hormones
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2
Q

describe the summary of events leading up to ovulation (6)

A
  1. FSH initiates follicle recruitment
  2. follicles all grow and begin to produce estradiol, which reduces FSH
  3. follicle selection and growth
  4. selected follicle acquires LH receptors and becomes LH dependent
  5. estradiol reaches a threshold that stimulates GnRH to produce an LH surge
  6. ovulation
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3
Q

follicular wave (4)

A
  1. recruitment
  2. growth
  3. selection
  4. either ovulation or atresia
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4
Q

describe summary of events after ovulation if no pregnancy (5)

A
  1. corpus luteum develops and produces progesterone, which inhibits LH
  2. follicular wave begins to occur
  3. lack of LH surge will prevent ovulation and selected follicle will undergo atresia
  4. uterus endometrium produces PG to kill CL
  5. once CL is reduced and progesterone levels decrease, the next follicular wave can undergo ovulation
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5
Q

describe summary of events after ovulation if pregnant (4)

A
  1. corpus luteum develops and produces progesterone, which inhibits LH
  2. follicular wave begins to occur
  3. lack of LH surge will prevent ovulation and selected follicle will undergo atresia
  4. corpus luteum will be maintained and sustain high levels of progesterone so that ovulation will continue to not occur
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6
Q

what happens to the selected follicle if the follicular wave is under high progesterone levels

A
  • no ovulation and follicle atresia
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7
Q

what happens to the selected follicle if the follicular wave is under low progesterone levels

A
  • ovulation of selected follicle
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8
Q

what are the feedback loops present in the estrous cycle (3)

A
  • E2 inhibits FSH
  • P4 inhibits LH
  • PG inhibits P4
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9
Q

what produces estradiol

A
  • follicles
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10
Q

what produces progesterone

A
  • corpus luteum
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11
Q

what produces GnRH, LH, and FSH

A
  • the brain/hypothalamus
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12
Q

what produces prostaglandin

A
  • uterus endometrium
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13
Q

luteolysis (3)

A
  • structural and functional degradation of corpus luteum
  • determines length of diestrus phase and the estrous cycle
  • sign of the end of a cycle or the end of pregnancy
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14
Q

what is the major luteolytic agent in most species (4)
- agent
- synthesis
- delivery
- inhibition

A
  • prostaglandin
  • synthesized by the uterus in the endometrium
  • delivered to ovaries through counter-current transfer in the plexiform structure
  • inhibited by conceptus in pregnant animals
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15
Q

what do follicle cells rearrange into in the corpus luteum (3)

A
  • large luteal cells
  • small luteal cells
  • fibrocytes (epithelial cells)
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16
Q

how does PG act on the CL (2)

A
  • PG membrane receptors present on luteal cells
  • binding of PG to receptors triggers pathway with G protein coupled receptor and kinases
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17
Q

what affects does the PG induced pathway have on the CL (3)

A
  • anti-angiogenesis affect: no new blood vessels
  • cell apoptosis: CL shrinks into a scar
  • shut down of steroidogenesis enzymes to halt P4 synthesis
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18
Q

phases of estrous cycle of the follicular phase (2)

A
  • proestrus
  • estrus
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19
Q

phases of estrus cycle of the luteal phase (2)

A
  • metestrus
  • diestrus
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20
Q

what is proestrus defined by (2)

A
  • high estradiol
  • low progesterone
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21
Q

what are the characteristics of proestrus (2)

A
  • preparation of mating
  • development of ovulatory follicle
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22
Q

what is estrus defined by (2)

A
  • highest estradiol
  • low progesterone
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23
Q

what are the characteristics of estrus (4)

A
  • acceptance of the male for mating and when mating occurs
  • visible behaviors of estrus
  • presence of large graafian follicle
  • ovulation occurs after estrus ends
24
Q

what is metestrus defined by (2)

A
  • low estrogen
  • low progesterone
25
Q

what are the characteristics of metestrus (3)

A
  • first few days after estrus
  • formation of the corpus luteum
  • bleeding
26
Q

what is diestrus defined by (2)

A
  • low estrogen
  • high progesterone
27
Q

what are the characteristics of diestrus

A
  • lasts until luteolysis
  • functional corpus luteum
  • associated with follicle turnover/atresia
28
Q

what are the phases of the estrus cycle (5)

A
  • proestrus
  • estrus
  • metestrus
  • diestrus
  • anestrus
29
Q

anestrus (3)

A
  • period of reproductive incompetence with no ovulation or corpus luteum formation
  • follicular waves DO occur, but all follicles undergo atresia/turnover
  • no expression of estrus behaviour
30
Q

anestrus (3)

A
  • period of reproductive incompetence with no ovulation or corpus luteum formation
  • follicular waves DO occur, but all follicles undergo atresia/turnover
  • no expression of estrus behavior
31
Q

what situations would the estrous cycle be in anestrus (3)

A
  • post-partum anestrus
  • seasonal anestrus
  • pseudopregnancy
32
Q

post-partum anestrus (3)

A
  • period of no ovulation after pregnancy so body/uterus can recover and focus resources on newborn
  • involution; uterus size recovery and shrinking
  • suckling effect from mammary glands sends negative neuro-endocrine signals to GnRH
33
Q

seasonal anestrus

A
  • light exposure alters melatonin levels in seasonal breeding animals, which affects GnRH and ovulation
34
Q

pseudopregnancy (2)

A
  • bitches can act pregnant due to high progesterone (no luteolysis)
  • no ovulation will occur during this period
35
Q

monoestrus

A
  • animals with only one estrus cycle per year
36
Q

polyestrus

A
  • animals with multiple estrus cycles per year
37
Q

monotocous

A
  • ovulation of ONE follicle
38
Q

polytocous (2)

A
  • ovulation of MANY follicles
  • amount varies between species and litters
39
Q

induced ovulators

A
  • ovulation depends on act of mating/copulation and not increased estradiol levels
40
Q

spontaneous ovulators

A
  • ovulation is hormonally driven
41
Q

what is the average length of estrus cycle (2)

A
  • about 3 weeks
  • determined by luteolysis
42
Q

what is the average duration of estrus (2)

A
  • 20 hours to 72 hours typically
  • some animals have 4-8 days on average, variable
43
Q

what is the average time of ovulation relative to estrus

A
  • 24 to 48 hours from start of estrus
44
Q

puberty: male

A
  • age with high testosterone and functional gametes
45
Q

puberty: female (2)

A
  • age at first estrus followed by ovulation
  • initiation of complete estrus cycles can be irregular (poor signs of estrus) at first, and then transition to become regular after a few cycles
46
Q

what occurs before puberty in females

A
  • follicular waves don’t complete due to GnRH blocking
47
Q

puberty variation (2)

A
  • varies among species, breeds, and individuals
  • depends on a variety of factors
48
Q

puberty endocrinology

A
  • hypothalamus and gonad control
49
Q

puberty endocrinology: female (3)

A
  • strong negative feedback on estradiol is reduced
  • rapid increase in steroidogenesis: estradiol for ovulation
  • timing is more related to body weight than age
50
Q

puberty endocrinology: male (3)

A
  • maturity of gonads (Leydig and sertoli cells in males)
  • gametogenesis becomes functional
  • rapid increase in steroidogenesis: testosterone for spermatogenesis
51
Q

LH pulse frequency before puberty (7)

A
  1. lots of E2 receptors on hypothalamus/pituitary; strong negative feedback on E2
  2. strong feedback inhibits follicle recruitment and growth; leads to lots of recruitment and atresia
  3. E2 receptors are reduced over time, weakening the negative feedback on E2
  4. recruited follicles are gradually able to grow more before atresia
  5. increased E2 induced GnRH to stimulate LH pulses
  6. follicle develops until it is close to normal cycle and close enough to trigger ovulation
  7. more frequent and larger pulses lead up to a LH surge, which triggers ovulation and puberty
52
Q

factors affecting initiation of puberty (4)

A
  • hormonal
  • genetics
  • nutrition
  • environmental
53
Q

factors affecting initiation of puberty: hormonal (4)

A
  • reduced GnRH release
  • reduced pituitary response
  • reduced ovarian response
  • pineal gland stimulus from melatonin
54
Q

factors affecting initiation of puberty: genetics (3)

A
  • inbreeding delays, while crossbreeding hastens (genetic diversity is better)
  • certain breeds vary
  • smaller breeds reach puberty faster than larger breeds as they reach mature body faster
55
Q

factors affecting initiation of puberty: nutrition (3)

A
  • underfeeding leads to a delay
  • optimum feeding will hasten
  • growth hormone, insulin and insulin growth factors will affect GnRH
56
Q

factors affecting initiation of puberty: environmental (5)

A
  • feed availability (nutrition)
  • temperature and humidity changes during seasons
  • confinement leads to delays
  • presence of male may hasten
  • cortisol and adrenaline will affect GnRH
57
Q

early induction of puberty

A
  • economic advantage for

APBI 312 (8 decks)

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