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Reproduction > 2.7 The Oestrus Cycle Pt. 2 > Flashcards

2.7 The Oestrus Cycle Pt. 2 Flashcards

1
Q

The time​ it takes for the follicle to become​ ovulated is

A

6 months

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2
Q

time​ it takes for follicles to become pre-ovulatory?

A

4 months

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3
Q

Little artresia happens between ___ and ___

A

Primordial and small antral

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4
Q

50-80 atresia​ happens between ___ and ____

A

little antral and large antral
- majority die

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5
Q

Antrum forms: Gonadotrophin-responsiveness

A

development continues without FSH, some atresia

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6
Q

antrum forms: Gonadotrophin-dependent:

A

become atretic if FSH falls; high atresia

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7
Q

What type of receptors do ovulatory follicles have?

A

Have LH receptors on granulosa cells and can survive without FSH

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8
Q

Ovulation happens in the presence of ?

A

an LH surge or artesia afterabout 72hrs

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9
Q

polyestrous​:

A

have regular estrus unless it’s interupted by pregnancy​

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10
Q

Polyestrus species:

A

cow, queen, pig, rodent

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11
Q

seasonal polyestrus:​

A

within breeding cycles they have multiple number of cycles

*If they don’t become pregnant after 1st ovulation, they have 2nd, and a 3rd, and so on until they become pregnant, or if they don’t​ become pregnant​ than the season is finished

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12
Q

seasonal Polyestrus species: long-day​ breeder

A

mare
- long day because​ they breed in spring and summer

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13
Q

seasonal polyestrous​: short-day breeder species

A

ewe, doe, elk, nanny
- short day because they breed in autumn

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14
Q

Moniestrus:

A

only have one cycle
- cycle is a bit longer
- if they miss a ​chance have to wait 6-7 months to have another cycle

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15
Q

monoestrus species:

A

dog, wolf, fox, bear

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16
Q

Which follicles can produce estradiol?

A
  • secondary/preantral follicles
  • antral follicles
  • preovulatory follicles

because they have both thecal cells and granulosa cells

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17
Q

What do the preovulatory cells respond to?

A

LH - allowing them to produce progesterone and cause ovulation

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18
Q

Key for folliculogenesis and ovaries function?

A

FSH and LH

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19
Q

KEY rules of receptors on follicular cells: Thecal cells ALWAYS

A

have LH receptors, never FSH

20
Q

KEY rules of receptors on follicular cells: Granulosa ALWAYS

A

have FSH receptors, LH receptors are acquired from mid-follicular phase onwards

21
Q

KEY rules of receptors on follicular cells: The dominant​ follicle

A

survives a fall in the levels of FSH by being able to respond to LH

22
Q

2 cell 2 gonadotropin theory:

A
  • LH binds to receptor on the ​Thecal cell and produces androgenm
  • Androgen then goes to the Granulosa cell and is converted to estradiol under the influence of FSH
23
Q

What is the substrate for prod​uction of steroid hormones?

A

cholesterol

24
Q

What makes a follicul become a dominant follicle​?

A

Like the lottery
- Right place
- Right Stage
- Receive right signal

25
Q

Under the influence of estradiol, granulosa cells which were previously unresponsive to LH acquire

A

LH receptors and become LH-responsive

26
Q

If there is a high level of estradiol that happens in the pre-ovulatory stage then

A

then the negative feedback becomes positive

27
Q

Early-mid follicular phase plasma estradiol (E2) exerts

A
  • exerts ​negative feedback on GnRH secretion
  • It acts mainly at the hypothalmus
  • Therefore FSH levels start to fall
  • The inhibitory effects of E2 occur only while the plasma E2 concentration is BELOW a certain threshold value
28
Q

Plasma concentrations rise ABOVE the threshold value:

A

cause E2 peak in the late follicular phase, it acts on the pituitary to STIMULATE gonadotrophin secretion

*This high level of estradiol ultimately gives rise to the surge in LH causeing the negative feedback to become positive feedback

29
Q

key event that induces follicular​ rupture?

A

surge in LH

30
Q

Ovulutaion occurs when the thin walls of the follicle___

A

rupture, the secondary oocyte surrounded by the zona pellucida are released​ into the oviduct

31
Q

LH surge consequence:

A

estradiol production then falls and progesterone starts to increase

32
Q

Luteal cells:

A

follicle cells that remain within the ovary are transformed through a process called luteinisation

33
Q

What happens before ovulation?

A
  • surge / Peak of LH is happening
  • LH causes the follicle to rupture and release the egg
34
Q

Once egg is released what has to happen in order for the egg to be fertilized.​

A

It has to be in the right stage:
- meiosis and develop to metaphase II
This is called oocyte maturation which initiates after LH surge

35
Q

If a follicle is ruptured what forms in place of it?

A

corpus luteum

36
Q
A
37
Q

large luteal cells are thought to arise from?

A

granulosa cells

38
Q

small luteal cells are thought to arise from

A

theca cells

39
Q

small luteal cells and large luteal cells ca produce?

A

progesterone

40
Q

Hormone that cause corpus litheum lysis?

A

PGF2 alpha cause CL to go down

41
Q

How is the CL causing its own death?

A
  • normally produces progesterone towards the end of the cycle when there is no pregnacy
  • Then produces oxytocin and binds to receptor in the uterine endometrium
  • this stimulates the production of PGF2 alpha
  • PGF2 alpha goes to CL and causes regression
42
Q

Which species have an estrus cycle of 21 days?

A

horse, cow, pig,

43
Q

Which species have an estrus cycle of 17 days

A

sheep

44
Q

Which species have an estrus cycle of 93 days

A

dog

45
Q

cow estrus stage:

A

12-36 hrs

46
Q

dog estrus stage:

A

7-13 d

47
Q

cow vs dog estrus stage:

A

cow = quite short
dog = monoesters have lengthy estrus cycle to allow more opportunity to become pregnant​

Reproduction (15 decks)

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