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Repro > The Luteal Phase of the Estrous Cycle > Flashcards

The Luteal Phase of the Estrous Cycle Flashcards

1
Q

what is the dominant hormone in the luteal phase?

A

P4

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2
Q

what part of the hormone cascade is ovvuring in a preovulatory follicle?

A

steroid synthesis of progesterone,which produces collagenase which acts on the theca interna

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3
Q

when is the corpus hemorrhagicum present?

A

1-3 days following ovulation, during metestrus

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4
Q

what is happening in the corpus hemorrhagicum? (4)

A
  1. blood vessels in follicle wall rupture
  2. walls collapse
  3. cells intermix
  4. old basement membrane becomes connective tissue of CL
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5
Q

is the corpus luteum larger or smaller than the corpus hemorrhagicum in most species?

A

larger for most species

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6
Q

what is the corpus luteum made of?

A

composed of cells from the granulosa and theca interna

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7
Q

what us the hormonal result of the CL?

A

progesterone production increases

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8
Q

does the small cavity present where the follicular antrum was have any effect on CL function?

A

no

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9
Q

what does SLC stand for?

A

small luteal cell

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10
Q

what does LLC stand for?

A

large luteal cell

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11
Q

where does P4 production take place (an organelle)

A

in the mitochondria of the CL

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12
Q

what do secretory granules of the CL contain and what is the function?

A

oxytocin: for cycling
relaxin: during pregnancy

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13
Q

what 2 things contribute to the functional capability of the CL?

A
  1. the number of luteal cells

2. vascularization of CL

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14
Q

what happens to large luteal cells in the CL?

A

they undergo hypertrophy (gorwing in size)

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15
Q

what happens to small luteal cells in the CL?

A

they undergo hyperplasia (increase in cell number)

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16
Q

what initiates vascularization of the CL?

A

angiogenic factors from follicle

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17
Q

what does CL vascularity effect?

A

CL steroid synthesis and delivery of hormones

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18
Q

what is the result of insufficient CL function? why?

A

failure to maintain pregnancy; won’t have adequate P4

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19
Q

list and describe the 2 targest of P4 stimulation

A
  1. mammary gland: extra alveolar development

2. uterine endometrium: secretions for early embryo

20
Q

list and describe the 2 targets of P4 inhibition

A
  1. myometrium: inhibit contractions

2. hypothalamus and anterior pituitary: negative feedback on surge AND tonic center, blocks estrus

21
Q

what 3 things are needed for luteolysis? describe their function if applicable
(2 hormones and an organ)

A
  1. uterus: produces PGF2a in response to oxytocin
  2. PGF2a
  3. oxytocin: targets uterus
22
Q

describe the lifespan of a CL in a normal uterus and in a uterus with a contralateral hysterectomy (remove opposite side than ovulated on)

A

CL will have normal lifespan

23
Q

describe the lifespan of a CL after a total hysterectomy after CL production

A

longer CL lifespan, similar to gestation length, due to no uterus producing PGF2a to lyse CL

24
Q

describe the lifespan of a CL after an ipsilateral hysterectomy (removal of same side ovulated on) after CL production

A

CL lifespan shorter, less than 35 days

25
Q

describe the 3 steps of PGF2a control of luteolysis in cows, sows, and ewes

A
  1. P4 causes production of oxytocin receptors in endometrium; oxytocin stimulates PGF2a release
  2. prostaglandin synthesized by uterine endometrium and released into the uterine vein
  3. PGF2a is picked up by ovarian artery through countercurrent exchange and delivered back to the ovary where it causes lysis of CL
26
Q

why does PGF2a circulate from the uterine horn on the side of ovulation directly into the uterine vein and artery of the CL?

A

is it metabolized very quickly in the lungs, so does not need to be in systemic circulation

27
Q

what happens to the formed CL in a mare after a hysterectomy?

A

the CL is maintianed

28
Q

what happens to formed CLs in a mare after either a contralateral or a ipsilateral hysterectomy?

A

50% of CLs maintained, doesn’t matter which side removed

29
Q

describe the blood supply to the uterus and ovary in the mare compared to other species

A

completely different, much more widespread vasculature

30
Q

describe the metabolization of PGF2a in the mare and what that means for the CL?

A

mares don’t metabolize PGF2a as efficiently as other species, so the CL is much more sensitive to PGF2a

31
Q

what is estromate?

A

a synthetic PGF2a used in cattle

32
Q

how much estromate is needed for CL regression in cattle?

33
Q

how much estromate is needed for CL regression in mares?

A

0.5 mL, MUCH LESS than cattle bc more sensitive

34
Q

on what days of the estrous cycle is PGF2a administration not effective for CL regression and only causes side effects for cows, ewes, and mares?

35
Q

how long are sows not responsive to PGF2a?

A

until day 12 of their estrous cycle

36
Q

when do sows produce their own PGF2a? what does this mean for administration of PGF2a?

A

day 15 of their estrous cycle; not really administered in sows

37
Q

list the 4 steps of luteolysis

A
  1. P4 production by CL
  2. towards end of diestrus (approx. d14) P4 causes endometrium to express oxytocin receptors
  3. oxytocin from CL causes production of PGF2a in endometrium
  4. PGF2a causes CL regression/lysis (cells die off)
38
Q

what 2 loops exist between oxytocin and PGF2a?

A

1, feedback loop

2. auto-amplification loop

39
Q

describe the feedback loop between oxytocin and PGF2a

A

PGF2a from uterus or exogenous origin induces oxytocin production in the CL, which induces more PGF2a release from the endometrium (positive feedback)

40
Q

describe the auto-amplification loop of PGF2a in the CL and endometrium

A

PGF2a from endometrium or exogenous origin induces PGF2a production in the CL in a self-sustaining loop

41
Q

what 3 things need to happen in luteolysis?

A
  1. decreased blood flow
  2. cellular response
  3. immune response
42
Q

describe the cellular response in luteolysis (2)

A
  1. apoptosis: increase, organized die off

2. Progesterone synthesis- decrease

43
Q

describe the purpose of the immune response in luteloysis and give the 2 cells that accomplish it

A

to clean up dead cells by phagocytosis; by lymphocytes and macrophages

44
Q

list the 2 differences between luteolysis in primates versus other animals

A

in primates:

  1. does not require the uterus
  2. CL lifespan in the human in 12-14 days unless pregnancy occurs
45
Q

what happens to the CL in the absence of pregnancy in primates?

A

CL self destructs via that auto-amplification loop

46
Q

what special thing does the human CL possibly contain and what is the purpose?

A

possible intra-ovarian oxytocin receptors and PGF2a production

47
Q

what stimulates the CL to stick around in humans?

Repro (18 decks)

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