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ANS 327: Reproductive Physiology > The Follicular Phase of the Estrous Cycle > Flashcards

The Follicular Phase of the Estrous Cycle Flashcards

1
Q

What are the four major events in the follicular phase?

A
  1. Elevated gonadotropin secretion from the AP. Is a result of GnRH.
  2. Sexual receptivity-behavior.
  3. Follicular growth and preparation for ovulation.
  4. Ovulation.
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2
Q

What is the driving force behind the initiation of the follicular phase?

A

Luteolysis (leads to decreased progesterone, removing the negative feedback loop, GnRH amplitude and frequency increases, increased LH and FSH initially, and increased E2).

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3
Q

If E2 is high, will it induce ovulation?

A

Not if P4 is present.

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4
Q

What is basal release?

A
  1. Throughout the cycle.
  2. Pulse every 1.5-2 hours during the follicular phase.
  3. Pulse every 6-8 hours during the luteal phase.
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5
Q
A
  1. Once perc cycle.
  2. Increased E2 and decreased P4.
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6
Q

When can atresia occur?

A

At any phase.

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7
Q

What is atresia?

A

Organized regression/death of the follicle.

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8
Q

What type of follicle most commonly undergoes atresia?

A

Primary.

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9
Q

What percentage of follicles in a cow undergo atresia during a cow’s reproductive life?

A

About 98%+.

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10
Q

What happens if a cow reaches 20-25 years of age?

A

She enters reproductive senescence.

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11
Q

What is the maximum number of oocytes a typical cow will ovulate during her reproductive life?

A

17 cycles/year * 8 years= 136 oocytes ovulated/lifespan.
*This assumes she was never pregnant.

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12
Q

What are three ways to extend a cow’s reproductive life?

A
  1. Ovum pickup.
  2. Superovulation (Rescue follicles from undergoing atresia with FSH treatment).
  3. IVF.
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13
Q

List the steps of antral follicle development in the order that they occur.

A
  1. Recruitment.
  2. Selection.
  3. Dominance.
  4. Ovulation.
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14
Q

What occurs during the recruitment step?

A

This is the phase when a group/cohort of small antral follicles begin to grow and secrete estradiol and inhibin.

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15
Q

What occurs during the selection step?

A

Recruited follicles get selected to become dominant or undergo atresia.

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16
Q

What occurs during the dominance step?

A

The large antral follicle is in the final stage of maturation.
Two paths:
1. Ovulate (high LH, Low P4).
2. Atresia (low LH, Low P4).
*Only one follicle reaches this stage.

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17
Q

What occurs during atresia?

A

Degeneration of the follicle prior to ovulation.

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18
Q

What are the two types of initial follicular growth?

A
  1. Spontaneous.
  2. Gonadotropin dependent, happens over a few days.
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19
Q

How many follicular waves occur in cattle?

A

2-3 waves.

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20
Q

What are the steps of the 2-cell 2-gonadotropin theory of steroid secretion?

A
  1. Theca cells always have LH receptors and will respond to LH to drive conversion of cholesterol to T.
  2. T will diffuse into granulosa cells which initially only have FSH receptors. FSH signals for the conversion of T to E2 via aromatase receptors. E2 will be elevated. In a dominant follicle at selection, granulosa cells will get LH receptors and can respond to the LH surge to induce ovulation.
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21
Q

What effects does E2 have on the repro. tract and brain?

A
  1. Increased blood flow (repro. tract).
  2. Leukocytosis-WBC or immune cells-Removal of foreign material.
  3. Genital swelling.
  4. Increased mucosal secretions-Vagina and cervix lubrication, flush out debris, sperm selection.
  5. Initiation of uterine gland growth.
  6. Elevated myometrial tone (Contraction for sperm transport).
  7. Lordosis (mating posture).
  8. Physical activity (restlessness).
  9. Phonation(vocalization).
22
Q

What is ovulation?

A

The process that results in the purposeful destruction of a follicle to release a COC.

23
Q

What is the stigma?

A

The protruding area that actually ruptures.

24
Q

How many layers make up the follicle?

A

6 layers.

25
Q

What events, if blocked, prevent ovulation?

A
  1. Protein synthesis.
  2. Steroid synthesis (E2 to P4 locally).
  3. Plasminogen activator synthesis.
  4. Prostaglandin synthesis.
26
Q

What does cumulus expansion indicate?

A

Hormone responsiveness.
* Allows the oocyte to separate from the follicular wall.

27
Q

What does the shift from E2 to P4 by the dominant follicle cause?

A
  1. Increased P4.
  2. Increased collagenase (breaks down the collagen holding the follicle together).
  3. Follicular wall weakens.
  4. Ovulation.
28
Q

What does the PGF2a increase do?

A

1a. Release of lysosomal enzymes.
2a. Follicular wall weakens.
3a. Ovulation.
1b. Contraction of smooth muscle.
2b. Follicular pressure (pushes fluid out).
3b. Ovulation.

29
Q

What does the histamine PGE2 increase do?

A
  1. Increased blood flow to the ovary and follicle due to increased vascular permeability.
  2. Increased edema.
  3. Follicular pressure (pushes fluid out).
  4. Ovulation.
30
Q

What animals are spontaneous ovulators?

A
  1. Bovines.
  2. Equines.
31
Q

What occurs during spontaneous ovulation?

A

Ovulating at a particular stage of the estrous cycle.
*Does not depend on mating.

32
Q

What animals are induced ovulators?

A
  1. Camel.
  2. Cats.
  3. Otters.
33
Q

What occurs during induced ovulation?

A
  1. Requires mating.
  2. Depends on long copulation or frequency.
  3. Physical induction.
34
Q

How are camels induced to ovulate?

A

A special chemical in the seminal plasma of males.

35
Q

What is the cascade for induced ovulators?

A
  1. Copulation stimulates the sensory neurons in the vagina and cervix.
  2. The impulses are sent to the spine.
  3. The impulses are relayed to the hypothalamic surge center.
  4. A GnRH surge occurs, resulting in an LH surge.
  5. Ovulation is induced.
36
Q

What is oogenesis?

A

The creation of a fertilizable oocyte.

37
Q

What is a primordial germ cell?

A
  1. A cell that gives rise to gametes.
  2. Forms prenatally.
  3. Migrates to the genital ridge.
    *Forms egg nests in females.
38
Q

What are oogonia?

A
  1. Undifferentiated germ cells that give rise to oocytes.
  2. Forms prenatally.
  3. Undergoes mitosis.
  4. Follicle cells surround it and initiate meiosis.
39
Q

What is a primary oocyte?

A
  1. An oocyte during the growth phase before it completes M1.
  2. Begins prenatally.
  3. Is most of the oocyte’s lifespan.
    *Many die at this stage.
40
Q

What is dictyate?

A

A developmental arrest during meiotic prophase one. A “hibernation” for nuclear maturation and development and cytoplasmic development.

41
Q

What is a secondary oocyte?

A

The oocyte that results after the completion of meiosis one.

42
Q

What are polar bodies?

A

A haploid cell that forms at the end of meiosis one. Cannot be fertilized due to uneven cytokinesis.

43
Q

What does GV stand for?

A

Germinal vesicle.
*Forms prior to meiosis one resumption.

44
Q

What does GVBD stand for?

A

Germinal vesicle breakdown.
*Occurs after an LH surge.

45
Q

What is the corona radiata?

A

The layer of cumulus cells directly touching the oocyte.

46
Q

What are transzonal projections?

A

Gap junctions in the zona pellucida that allow the oocyte and the corona radiata to communicate.

47
Q

What does MPF stand for?

A

Meiosis/Maturation Promoting Factor.

48
Q

What happens before the LH surge causes the resumption of meiosis one?

A
  1. The corona raidata have open gap junctions that allow cAMP to move from the corona radiate to the oocyte.
  2. The oocyte has cAMP, leading to increased cAMP.
49
Q

What happens after the LH surge that causes the resumption of meiosis one?

A
  1. Gap junctions close.
  2. cAMP decreases.
  3. MPF is activated.
50
Q

What do the two pronuclei contain?

A
  1. One contains male DNA.
  2. One contains female DNA.

ANS 327: Reproductive Physiology (23 decks)

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