Lecture 5: Female Reproductive Physiology: The Luteal Phase Flashcards

1
Q

what happens in metestrus period of estrous cycle

A

CL forms and begins to secrete progesterone

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2
Q

What happens in diestrus period

A

Sustained luteal secretion of progesterone, CL develops during metetrus with optimal function during diestrus

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3
Q

Are estrogen levels low or high during metetrus

A

Low

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4
Q

What are progesterone levels during metetrus

A

Start low but quickly appears with corpus hemorrhagicum

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5
Q

What are FSH levels in metetrus

A

Low but may be sufficient to trigger recruitment for next follicular wave

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6
Q

What are progesterone levels during diestrus

A

High

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7
Q

What are estradiol levels during diestrus

A

Low and may fluctuate with follicular cycles

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8
Q

Do progesterone levels need to be high or low to suppress ovulation

A

High

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9
Q

When does the corpus luteum reach maximum size

A

Diestrus

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10
Q

Elevated ____ inhibits final follicular development preventing ovulation and estrus

A

Progesterone

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11
Q

If there is no pregnancy at end of diestrus what regresses and what hormone causes the regression

A

CL regresses due to PGF2alpha being released by uterus

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12
Q

What is responsible for breakdown of follicle wall, tunica, albuginea and surface epithelium during LH surge/ovulation

A

Cytokines and hydrolytic enzymes

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13
Q

Basal laminate of mural ___-cells are degrades during LH surge

A

Granulosa

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14
Q

What do granulosa cells secrete to increase blood supply to the new corpus luteum

A

Vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF)

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15
Q

vascularization of follicle is critical to

A

Steroid synthesis and secretion

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16
Q

Cholesterol is delivered to ___ cell and taken in by ___ and ___ receptors

A

Luteal, LDL and HDL receptors

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17
Q

LH stimulates steroidogenesis by activating ____

A

Cholesterol desmolase

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18
Q

What enzyme is necessary for progesterone synthesis

A

3B-hydroxysteroid dehydrogenase

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19
Q

What are the targets of progesterone

A

Hypothalamus, anterior pituitary, mammary glands, uterus

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20
Q

What is the role of progesterone on hypothalamus

A

Acts as a negative feedback inhibiting estrogen priming

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21
Q

How does progesterone act on anterior pituitary

A

Negative feedback of LH, FSH

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22
Q

What does progesterone do to mammary glands

A

Acts in positive feedback loop to promote alveolar development

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23
Q

How was progesterone act in the uterus

A
  1. Negative feedback on myometrium
  2. Positive feedback on endometrium which promotes conditions that are food for fertilized eggs
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24
Q

What is relaxin

A

Hormone that targets the uterus, soft CT and acts synergistically with progesterone to maintain pregnancy. Prepares soft tissue of the pelvic canal for eventual birth

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25
What species produces relaxin in corpus luteum
Cows
26
What maintains the corpus Luteum
Basal (moderate) secretion of LH
27
What species only require LH to maintain CL
Horses, cat and cow
28
What species require LH and prolactin to maintain CL
Dog, sheep, rodents
29
What maintains LH levels that are needed to maintain Corpus luteum
Pulses of GnRH maintain LH at moderate levels
30
___ terminates CL and progesterone secretion at end of luteal phase
PGF2alpha
31
What does corpus luteum become after exposed to PGF2alpha
Corpus albicans
32
What produces PGF2alpha in cows, horses and sheep
Endometrium
33
What produces PGF2alpha in primates
Ovaries
34
What is the stimulus for PGF2alpha
Estrogen/progesterone then oxytocin
35
What is the target of PGF2alpha
Corpus luteum
36
What is the effect of PGF2alpha on corpus luteum
Luteolysis
37
What are the two mechanisms of actions/effects of PGF2alpha
1. PGF2alpha- receptor complex opens Ca2+ channels in granulosa cells. This induces apoptosis through high intracellular calcium 2. Activation of Protein kinase C inhibits mitochondrial transport of cholesterol and progesterone synthesis
38
How does oxytocin induce PGFalpha- describe feedback loop
1. Signal from posterior pituitary to uterus 2. Uterus releases PGF2alpha 3. PGFalpha signals release of oxytocin to act in positive feedback to uterus to release more PGF2alpha 4. PGF2alpha destroys CL via a positive feedback loop
39
When does CL become receptive to PGF2alpha in cows
PGF receptors appear ~ 6 days after ovulation
40
When does CL become receptive to PGF2alpha in horses
PGF2alpha receptors appear~ 5 days after ovulation
41
If you inject a cow with PGF2alpha 3 days after ovulation what happens
Not much, don’t have PGF2alpha receptors yet
42
If you inject a cow with PGF2alpha 10 days after ovulation what happens
Will be able to respond and cause CL to regress due to presence of receptors 6 days after ovulation
43
What is the vascular pathway for PGF2alpha in cow and sheep
Produced in the uterus endometrium is released into the ovarian veins and is transferred to ipsilateral ovarian artery through counter current exchange mechanism
44
What is the vascular pathway of PGF2alpha in horses
Released in systemic blood from either uterine horn
45
Absence of both uterine horns (full uterectomy) leads to ___luteal phase, why?
Prolonged because can’t send PGF2alpha from uterine horns into systemic blood, therefore Cl/luteal phase won’t be induced to regress, no oxytocin positive feedback loop. Diestrus is 148 days long
46
Absence of the uterine horn contralateral to the CL does what to lifespan of CL
Nothing, present uterine horn is on same side as CL therefore can secrete PGF2alpha to that CL to cause regression. Days 15-17
47
Absence of uterine horn ipsilateral to CL does what to lifespan of CL
Slightly prolongs it to 35 days because still have other uterine horn that will be active during next cycle
48
Endometritis in cows leads to ___luteolysis. Why?
Decreased, because endometrium is responsible for releasing PGF2alpha so if damaged will have decreased release of PGF2alpha and prolonged luteal
49
What does E. Coli exposure in cattle do to luteotrophic prostaglandin E2 (PGE2) and luteolytic PGF2alpha
Increases PGE2 and has no effect on PGF2alpha
50
During pseudopregnancy there is no ____ mechanism
Uterine luteolytic
51
Pseudopregnancy is associated with what behaviors
Nesting, spontaneous lactation and maternal protection
52
When does pseudopregnancy occur
50-90 days after estrus
53
What happens to progesterone and prolactin levels during pseudopregnancy
Decreasing progesterone levels and increasing prolactin levels after long luteal phase
54
How do wild canids exhibit an adaptive role for pseudopregnancy
Subordinate females exhibit elevated progesterone during dominant females pregnancy
55
Where is prolactin secreted from in late stage pregnancy in the bitch and rat
Anterior pituitary or the endometrium
56
What is the stimulus for prolactin in the bitch
Increasing estrogen late in diestrus
57
What is the stimulus for prolactin in rodents
Copulation that initiates a 9-15 day pseudopregnancy in absence of fertilization
58
What is the target of prolactin
CL in the rat, bitch and ewe, mammary glands in all mammals
59
What is the effect of prolactin
Luteotropic. Required for initiation and maintenance of milk synthesis
60
What types of drugs can be used to induce estrus in the bitch
Anti-prolactin drugs (dopamine agonists and serotonin antagonists)
61
If anti-prolactin drugs are given mid pregnancy what will happen
Luteolysis and abortion
62
What does estradiol increase in canine estrous cycle
Proestrus
63
When does progesterone increase in canine estrous cycle
End of estrus and peaks at beginning of metetrus
64
When does LH increase in canine estrous cycle
End of estrus to induce ovulation
65
How can you induce pseudopregnancy in rodents
Tactile stimulation of vagina
66
Ovulation is induced by ___
LH surge
67
Decide all endometrial ___maintains murine pseudopregnancy
Prolactin