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Nerd Alert > Bovine Reproduction > Flashcards

Bovine Reproduction Flashcards

1
Q

When can cyclicity of oestrus cease?

A
  • Pregnancy
  • Nursing
  • Season- some species
  • Nutrition
  • Stress
  • Pathologic conditions
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2
Q

What are the different types of oestrus cycles?

A
  • Polyoestrus- constant- cows, cats, rodents
  • Seasonal polyoestrus- mare/sheep- long/short days
  • Monoestrus- dogs
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3
Q

How can the oestrus cycle be divided into 2 distinct phases?

A

Follicular Phase:
* period from the regression of corpora lutea to ovulation
* Primary ovarian structures are growing dominant follicles that produce oestradiol

Luteal Phase
* Period from ovulation until corpus luteum regression
* Dominant ovarian structures are the corpus luteum
* Primary repro hormone is progesterone
* follicles continue to grow and regress but do not produce high amounts of estradiol

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4
Q

What is the difference between oestrogen and oestradiol?

A
  • Oestrogen is a type of sex hormone which has 3 types
  • Oestrone (E1)
  • Oestradiol (E2)
  • Oestriol (E3)
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5
Q

When does the follicular phase commence and what does it cause?

A
  • After luteolysis
  • Causes a decline in progesterone
  • Gonadotrophins (FSH and LH) are therefore produced that causes follicles to produce oestrogen
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6
Q

What hormone dominates the follicular phase?
When does the follicular phase end?

A
  • E2 (oestradiol)
  • Follicular phase ends at ovulation where the luteal phase commences
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7
Q

When does the luteal phase start?
What does it include?
What causes luteolysis to end the luteal phase?

A
  • After ovulation
  • Includes the development of the corpus luteum
  • prostaglandin F2alpha causes luteolysis
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8
Q

How can the oestrus cycle be divided into four stages?

A

Follicular phase: proestrus and oestrus

Luteal phase: Metoestus and Diestrus

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9
Q
  1. When does proestrus begin?
  2. What ‘characterises’ proestrus?
  3. What happens during proestrus?
A
  1. Luteolysis- progesterone declines
  2. Endocrine transition- progesterone to oestrogen dominance
  3. Follicles recruited for ovulation and female repro system prepares for oestrus
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10
Q
  1. What is the dominant hormone durine oestrus?
  2. What is standing oestrus?
A
  1. Oestrodiol
  2. Willingness to accept the male for mating
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11
Q

What occurs during metoestrus?

A
  • During early metoestrus progesterone and oestrogen are low
  • The newly ovulated follicle undergoes cellular and structural remodelling forming the corpus luteum
  • This process is called lutenization
  • Progesterone secretion is detectable soon after ovulation
  • But 2-5 days before corpus luteum produced significant quantities
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12
Q

What occurs during dioestrus?

A
  • CL fully functional
  • Progesterone secretion high
  • Ends with luteolysis
  • High progesterone prompts the uterus to prepare a suitable environment
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13
Q

What is silent ovulation?

A
  • Following seasonal anoestrus in the ewe or pregnancy in a cow
  • Ovary develops a follicle that ovulates without behavioural oestrus
  • The CL produced primes the brain enabling E2 for the next ovulatory follicle
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14
Q

What is lactational anoestrus?

A
  • Cyclicity is delayed by a nursing neonate
  • Causes inhibition of GnRH
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15
Q

What ‘governs’ the follicular phase?

A
  • The hypothalamus and anterior lobe of the pituitary and ovary control the production of oestrodiol in the absence of progesterone
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16
Q

What does the hypothalamus release for the oestrus cycle?

A

GnRH

17
Q

What are the two different centres of the hypothalamus that control GnRH release?

A

Tonic GnRH centre:
* responsible for basal secretion of GnRH

Surge centre:
* responsible for the preovulatory causing LH surge
* Releases basal until positive stimulus
* Positive stimulus is high oestrogen with low progesterone

18
Q

Describe the release and control of FSH and LH during the follicular phase

A
  • GnRH pulse frequency increases due to low progesterone
  • FSH and LH secreted from anterior lobe
  • Oestrodiol released from follicles
  • The gonadotrophins have postitive feedback causing GnRH release
  • Follicle releases oestrodiol and later on inhibin which causes negative feedback on FSH
19
Q

Describe the hormonal changes during oestrus

A
  • Recruited follicles develop dominance
  • Produce oestrodiol and inhibin
  • Supress FSH- does not surge like LH
  • When oestrogen reaches a threshold peak preovulatory surge of LH occurs
20
Q

What do the dynamics of antral follicles consist of?

A
  • Recruitment
  • Selection
  • Dominance
  • Atresia
21
Q

Describe the process of recruitment, selection and dominance of follicles

A

Recruitment
* Small antral follicles are recruited from ovarian pools
* Produce small amounts of E2
* Some atresia

Selection:
* Follicles are selected from pre-viously recruited small follicles
* Develop further- moderate E2
* Some become atretic

Dominance:
* Selected follicles that do not become atretic become dominant and produce large amounts of E2
* Dominant follicles will ovulate

22
Q

Why during the first two follicular waves does full development and ovulation not occur?

A
  • Begin and terminate during times in the cycle when progesterone is increasing or at highest point
  • Dominant follicle will ovulate if luteolysis occurs
23
Q

Are the FSH, LH and inhibin high or low during:
1. Recruitment
2. Selection
3. Dominance

A
  1. Recruitment- high FSH, low LH, no inhibin
  2. Selection- low FSH, moderate LH, low inhibin
  3. Dominance- low FSH, high LH, high inhibin
24
Q

What do each of the images show?

A

Top:
* Ovary containing small antral follicles (SF)

Middle:
* Ovary contains three medium antral follicles MF
* An a corpus luteum

Bottom:
* Contains a dominant follicle
* OS- ovarian stroma

Nerd Alert (4 decks)

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