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Exam block 3 > Exam 2: Lecture 23: Ovulation, Luteinization, And Leutolysis > Flashcards

Exam 2: Lecture 23: Ovulation, Luteinization, And Leutolysis Flashcards

1
Q

Ovulation is ___ dependent

A

LH surge

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2
Q

How long does ovulation last?

A

-In most species, 24 hour event except in Mare it is 3-5 day elevation
-The bitch ovulates 2-3 days AFTER LH surge

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3
Q

When do most species ovulate?

A

-During estrus (except cow)

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4
Q

What happens to the ovulated follicle during ovulation?

A

-Collapses
-Fills with blood
-Becomes Corpus Hemorrhagicum (CH)

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5
Q

___ is critically important in ovulation b/c it sets in motions a series of biochemical events that lead to ovulation

A

Preovulatory LH surge

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6
Q

______ is a complicated process that involves purposeful destruction of follicular tissue

A

Ovulation

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7
Q

What brings on ovulation?

A

-Elevated blood flow
-Breakdown of connective tissue
-Ovarian contractions

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8
Q

What do induced ovulators require for ovulation to occur?

A

-Require stimulation of vagina, cervix, and/or uterus

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9
Q

What animals are induced ovulators?

A

-Cats
-Rabbits
-Minks
-Ferrets
-Giant Fruit Bats
-13-lined Ground Squirrel (Chipmunks)
-Sumatran Rhinos
-Camelids

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10
Q

What else do camelids require in addition to stimulation for ovulation?

A

-Also require a substance in seminal plasma for ovulation
-Ovulation inducing factor (OIF)
-Beta-Nerve growth factor (B-NGF)

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11
Q

Cats have a ___% ovulation rate if they are mated once

A

50%

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12
Q

What are the steps of induced ovulators?

A
  1. Copulation stimulates sensory nerves in vagina & cervix
  2. Impulses are then relayed to spinal cord
  3. Impulses are then relayed to surge center in hypothalamus
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13
Q

What is the Luteal Phase?

A

-Metestrus & Diestrus

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14
Q

What are the 3 main events of the luteal phase?

A
  1. Luteinization of follicular cells to luteal cells
  2. Growth & development of CL & production of Progesterone
  3. Luteolysis
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15
Q

When does the luteal phase begin?

A

-Immediately after ovulation

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16
Q

What happens during early luteal phase?

A

-CL develops (Luteinization) & progesterone increases

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17
Q

What happens during the mid luteal phase (diestrus)?

A

-CL is full functional & progesterone plateaus

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18
Q

What happens during the last 2-3 days of the luteal phase?

A

-Destruction of CL occurs (luteolysis) & luteal phase terminates & proestrus is initiated (follicular phase is resumed)

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19
Q

The corpus luteum originated from

A

-An ovulatory follicle

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20
Q

____ begins to breakdown as ovulation nears in the formation of the CL

A

Basement membrane

21
Q

What happens in corpus hemorrhagicum?

A

-Small blood vessels rupture and the Theca and Granulosa cells mix

22
Q

What is the “Functional Corpus Luteum (CL)”?

A

-Mixture of large luteal cells (LLC) originating from Granulosa cells & Small luteal cells (SLC) originating from Theca cells
In some cases, there is remnant of follicular antrum that forms small cavity in center of CL

23
Q

What is luteinization?

A

-Transformation of Theca International & Granulosa cells (that produced Estrogen prior to ovulation) to Luteal cells producing Progesterone

24
Q

Where does the corpus luteum originate and what does it produce?

A

-Originated from ovulatory follicle
-Both large & small luteal cells produce progesterone
-Other hormones produced by the CL include Oxytocin & Relaxin

25
What is shown here? (cow)
-Corpora Hemorrhagicum (CH)
26
What is shown here? (Cow)
-Developing Corpus Luteum
27
What is shown here? (Cow)
-Corpus Luteum during peak luteal phase & peak progesterone production
28
What is shown here? (Cow)
-Regressing Corpus Luteum
29
What is shown here? (Sow)
-Developing Corpora Lutea
30
What is shown here? (Sow)
-Corpora Lutea during high secretory activity
31
What is shown here? (Sow)
-Regressing Corpora Lutea
32
What is shown here? (Mare)
-Corpora Hemorrhagicum (CH)
33
What is shown here? (Mare)
-Developing Corpus Luteum *does not protrude from the surface*
34
What is shown here? (Mare)
-Inner tissue mass of the Corpus Luteum -(Some have a cavity & some do not)
35
What is shown here? (Mare)
-Regressing Corpus Luteum
36
What is the physiologic effect of Progesterone on the hypothalamus?
Negative feedback -Reduces basal GnRH amplitude & frequency -Prevents behavioral estrus -Stops preovulatory LH surge
37
What is the physiologic effect of Progesterone on the anterior pituitary?
-Negative feedback
38
What is the physiologic effect of Progesterone on the Uterus?
-Positive influence on uterine glands to secrete "uterine milk" for potential conceptus -Reduces myometrial tone (except Mare)
39
What is the physiologic effect of Progesterone on the mammary glands?
-Prior to parturition causes final alveolar development
40
What is luteolysis?
-Destruction of the CL -Essential in order to return to new follicular phase (disintegration of the CL, dramatic drop in blood progesterone)
41
What is the luteolytic agent in domestic animals?
-PGF2a
42
What are sources of PGF2a?
-**Uterine endometrium in domestic animals is the MAJOR source** -Dog uterus appears not to be involved in luteolysis -Human PGF2a is made by the ovaries
43
What happens during luteolysis?
-Cessation of progesterone secretion -Structural regression to form a corpus albicans -Removal of negative feedback by progesterone upon GnRH secretion resulting in new follicular phase
44
What is the pathway to luteolysis?
(Varies by species) -Local countercurrent exchange of PGF2a from ipsilateral uterine vein & ovarian artery in ruminants -Systemic pathway in the mare -Combination of local & systemic in sow
45
What is the mechanism of luteolysis in ruminants?
-Vascular countercurrent exchange mechanism -Low molecular weight substances in high concentrations in one vessel diffuse into adjacent vessel of lower concentration -Allows PFG2a secreted by uterus to be transported directly to ovary & CL w/out dilution by systemic circulation -Portion of PGF2a transported directly from utero-ovarian vein into ovarian artery where it has direct lytic effect on the CL
46
What is the mechanism of luteolysis in mares?
-Systemic pathway only -CL is more sensitive to PGF2a -PGF2a is metabolized less rapidly (low 1st pass dilution rate)
47
What is the mechanism of luteolysis in the sow?
-Systemic & countercurrent exchange pathways -Medium 1st pass dilution rate (~40%) -Corpora lutea are not responsive to pGF2a until at least Day 12 post ovulation
48
____ causes luteolysis during about 60% of the Estrous cycle in most species
Exogenous PGF2a
49
Luteolysis is most potent after day ___ post ovulation, therefore almost always causes luteolysis if administered after this time
Day 5

Exam block 3 (39 decks)

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