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ANS3319C Reproductive Physiology and Endocrinology > The Luteal Phase > Flashcards

The Luteal Phase Flashcards

1
Q

What does the luteal phase consist of?

A
  1. Luteinization (formation of the CL)
  2. Synthesis and secretion of large quantities of P4
  3. Luteolysis
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2
Q

How does the Corpus hemorrhagicum form? What does it do immediately?

A
  1. It is formed after follicle rupture
  2. Immediately precedes CL formation.
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3
Q

During the luteal phase how does it start and in which order does it go in and how does it end?

A
  1. Starts with Ovulation
  2. Goes into Metestrus
  3. Goes into Diestrus
  4. goes into Pro-estrus
  5. Ends with Ovulation
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4
Q

Under Metestrus what occurs

A

There is CL formation (lutenization),
Starts to slowly increase progesterone

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5
Q

What occurs under Diestrus?

A
  1. Progesterone is increased
  2. Luteolysis ends the phase and starts to lower the progesterone production
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6
Q

What occurs under the pro-estrus?

A

Progesterone production is at its lowest

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7
Q

Where does the Corpora lutea come from?

A

They originate from the follicular theca interna and granulosa cells

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8
Q

What occurs during the preovulatory follicle?

A
  1. Breakdown basement membrane- dependent on LH
  2. Theca interna & granulosa cells mix
  3. Ovulation: tunica albuginea ruptures
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9
Q

What occurs during the Corpus Hemorrhagicum (CH)?

A
  1. Theca interna & granulosa mix
  2. Follicle walls collapse, folds on itself
  3. Basement membrane becomes -> connective tissue
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10
Q

What occurs during the corpus luteum formation?

A
  1. Granulosa cells become large luteal cells (LLC)
  2. Theca interna cells become small lutela cells (SLC)
  3. Vascularization increases
  4. Both large and small luteal cells are steroidogenic
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11
Q

What is the function capacity of CL? What is it driven by and what increases?

A
  1. Ability to produce progesterone
  2. Driven by LH
  3. Progesterone increases as CL volum increases
  4. If small LC increases hyperplasia, if large increases hypertrophy
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12
Q

What occurs during the vascularization of CL?

A
  1. Amount varies, due to angiongenic factors in follicular fluid
  2. Insufficient luteal function results in decreases progesterone
  3. Inability of uterus to support pregnancy
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13
Q

For Large luteal cells where is its origin? In ruminants what does it act as? How does it act if pregnant, in estrous cycle or not pregnant?

A
  1. Granulosa cell origin
  2. Acts as secretory granules
    * If pregnant produces relaxin
    * If in estrous cycle produces oxytocin
    * If not pregnant it kicks out oxytocin and sends signals to reduce CL
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14
Q

During the hypertrophic growth of the large luteal cells what occurs?

A
  1. > 80% progesterone is produced
  2. High basal progesterone
  3. No LH receptors
  4. Growth hormone receptors
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15
Q

With Small luteal cells (SLC) where do they originate? What do they contain ?

A
  1. They originate in the thecal cell (they may turn into a large cell, not often)
  2. Contain lipid droplets
  3. Contains no secretory granules
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16
Q

During the hyperplastic growth of the small luteal cells what happens?

A
  1. < 20% progesterone
  2. Low basal progesterone
  3. LH receptors
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17
Q

When it comes to luteal cell physiology what is the difference between cattle and primates?

A
  1. CL can be easily palpated in cows but not in primate
  2. Palpation in cattle can identify a CL, but not determine the functional status
  3. Theca and granulos cells do not “mix” in primates but are easily distuinguised upon CL formation
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18
Q

What is the degree of CL function dependent upon?

A
  1. The numbers of luteal cells
  2. Degree of CL vascularization
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19
Q

What occurs if the luteal function is not enough?

A

Insufficeint lutel function contributes to reporductive failure

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20
Q

What are the some primary targets of P4 after CL production?

A
  1. Hypothalamus
  2. Reproductive tract
  3. Mammary Gland
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21
Q

What does progesterone do to the hypothalamus?

A
  1. Decreases basal GnRH secretion (amplitutde & frequency)
  2. Prevents preovulatory LH surge (ovulation)
  3. Prevents behavioral estrus
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22
Q

How does P4 affect the Reproductive tract after CL production?

A
  1. Incrases uterine glandular epithelium, provides environment for embryo
  2. Decreases myometrial contractility (prostaglandin is important)
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23
Q

How does P4 affect the mammary gland?

A
  1. Induces alveolar development
  2. Last 1/3 gestation
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24
Q

What does P4 inhibit?

A
  1. GNRH
  2. Behavioral Estrus
  3. LH surge
  4. Myometrial contractions in most species
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25
Q

In order for progesterone to be synthesized by luteal cells it requires?

A
  • Basal (tonic) LH secretion
  • Cholesterol (remember it’s a steroid precursor)
26
Q

What is the order of the mechanism of P4 synthesis by the luteal cells?

A
  1. Cholesterol is delivered to the luteal cell by LDL
  2. LDL binds to cell membrane receptors (R)
  3. LDL + R internalized
  4. Cholesterol is released as a cholesterol ester
  5. The LDL receptor is recycled so it can transport more cholesterol
27
Q

What happens after the first step of P4 synthesis ? What are the next 3 steps?

A
  1. LH binds to its receptor on the plasma membrane
  2. G- protein activation in turn activates (adenylate cyclase) to convert ATP to cAMP
28
Q

After ATP turns into cAMP what occurs?

A
  1. cAMP activates protein kinase enzyomes which does 3 things:
    * Accelerates LDL- cholesterol receptor internalization
    * Activates cholesterol esterase to cleave cholesterol from its ester
    * Promotes entry of cholesterol into the mitochondria
29
Q

What does the mitochondria contain that is important with cholesterol?

A
  1. Contains enzymes that converts cholesterol to pregnenolone (PREG)
30
Q

After pregnenolone is formed within the mitochondria what occurs? What occurs after the next process?

A
  1. PREG leaves the mitochondria where it is converted enzymatically to progesterone by the smooth endoplasmic reticulum
  2. Progesterone leaves the theca cell and enters the blood stream to target tissue
31
Q

What does Luteolysis mean?

A
  1. The loss of progesterone secretion by the CL
  2. Loss in luteal tissue mass
32
Q

What hormones induce luteolysis in farm animals? What are the exceptions?

A
  1. Prostaglandin F2alpha (PGF2alpha)
  2. Primate, dog, cat
33
Q

Where does prostaglandin F2alpha (PGF2alpha) come from? What does it target?

A
  1. Comes from the uterus
  2. Targets the CL
34
Q

What is the Uterus required for? What type of organ is it?

A
  1. Required for luteolysis
  2. Uterus is an endocrine organ that must communciate with the CL
35
Q

What does the procedure of the Uterectomy do?

A
  1. Extends the luteal phase
  2. Prevents luteolysis (not in dogs or humans)
36
Q

How does the location of the uterine horn play a roll in the communication with the CL?

A
  1. If removed the uterine horn contralateral (opposite) to CL, the lifespan is unaffected (15-17 d)
  2. If removed the uterine horn ipsilateral (same side) to CL, Increases CL lifespan (35 d)
37
Q

If the uterus is intact what is the difference between a normal cycle and itself?

A

The CL lifespan is the same as in a normal cycle 15-17 d (no difference)

38
Q

In a total uterectomy how does it affect the CL lifespan?

A

With a total uterectomy, the CL lifespan is similar to a normal gestation length (148 d)

39
Q

In order for the uterus to be effective what must be ?

A

The uterus must be near the ovary with the CL

40
Q

In primates where is Prostaglandin F2α (PGF2α) secreted?

A

It is secreted from the ovary not the uterus when it comes to primates

41
Q

What is used for the PGF2α to reach the ovary? Which animal does it no apply to?

A
  1. The Utero-Ovarian Vascular Countercurrent Transport System
  2. The mare
42
Q

How does the Vascular counter current exchange work?

A
  1. Diffusion PGF2α from uterine vein to ovarian artery
  2. Ensures maximum PGF2α to CL without dilution
  3. Goes from High gradient to Low gradient (PGF2α)
43
Q

What is the Vascular counter current exchange necessary?

A
  1. The majority of PGF2α contains no diffusion (is metabolized)
  2. Is denatured after one pass through lungs
44
Q

In Mare how is PGF2α different?

A
  1. It is not metabolized as rapidly
  2. CL is less sensitive
45
Q

In subprimates (everything that is not primate related) :

A
  1. There is a presence of oxytocin receptors
  2. Critical level of luteal oxytocin (from LLC)
  3. Uterine PGF2α synthesis
46
Q

When it comes to the presence of oxytocin receptors in uterus how is it important?

A
  1. Important due to the fact that it could be possibly blocked due to increases progesterone 1st half of the cycle, which blocks PGF2α and its ability to increase oxytocin receptor synthesis
  2. Progesterone decreases, oxytocin receptors increase, bind oxtocin which increases PGF2α release
47
Q

What does P4 prevent secretions of?

A

Prevents secretions of PGF2α from the uterus by blocking the formation of uterine oxytocin receptors

48
Q

What does PGF2α have a positive relationship with?

A
  1. Increases PGF2α production
  2. Uterine oxytocin receptors
49
Q

What are intracellular mechanisms that induce luteolysis (death or regression of luteal cells)?

A
  1. Reduced blood flow to CL (functional regression)
  2. Inhibition of progesterone synthesis (functional regression)
  3. Immune response (structural regression)
50
Q

What does reduced blood flow to CL cause?

A
  1. Causes vasoconstrictive actions of PGF2α (starve CL of nutrients)
  2. Capillary degeneration of luteal tissue
51
Q

What does the inhibition of progesterone synthesis (functional regession) do?

A

1.PGF2α binds to LLC
* Has a negative effect on the enzyomes that induces progesterone synthesis

52
Q

During the immune response (structural regression) what is present?

A
  1. Macrophages/lymphocytes are present in the CL
    * Produces cytokines (non-antibody proteins)
    * Causes cell death in vitro, reduced progesterone synthesis
    * Stimulates Apoptosis (programmed cell death ‘contains bicohemical and morphologic changes occuring to the cell’ )
    * Increases phagocytosis of damaged luteal cells (action: forms corpus albican formation)
53
Q

What type of event is luteolysis considered?

A

Considered an intraovarian event

54
Q

Does a Uterectomy affect cyclicity?

A

It does not influence cyclicity and it ontinues in 28d intervals

55
Q

When the pituitary oxytocin increases ovarian receptors?

A
  1. Result in higher intraovarian PGF2α
  2. Intiates luteolysis -> decreases progesterone
  3. Endometrial release of PGF2α
    * Vasoconstriction on endometrial arterioles & initiates menstruation
    * Endometrial necrosis & sloughing (menses)
56
Q

What can cause the CL to induce luteolysis?

A

The Oxytocin from the posterior pituitary exerts local effect on the CL to induce luteolysis

57
Q

Vasoconstriction causes?

A
  1. Degradation
  2. Sloughing of the endometrial lining
58
Q

We can produce an “aritfical corpus luteum” by administering _________________ to synchronize estrous cycles in battle

A

Progesterone

59
Q

What is the tool used to initiate estrous?

A

CIDR (Controlled intravaginal drug) is used since it contains Progesterone

60
Q

Regu-Mate is a synthetic __ ___ used in mares primarily to suppress estrus behavior (oral ingestion)

A

Progesterone

61
Q

What is a way to perform timed artifical insemination in dairy cattle without having to heat check ? What is a benifit of this method?

A
  1. Manipulation of the reproductive cycle with exogenous administration of hormones can allow for timed AI
  2. Increased pregnancy rates and better herd managment.

ANS3319C Reproductive Physiology and Endocrinology (13 decks)

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