Ovarian function and its control Flashcards

1
Q

What is a corpus luteum?

A

-Forms once a dominant follicle has ruptured.
-It is highly vascularised
-Transient endocrine gland
Produces progesterone

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2
Q

Describe early germ cell development

A
  • Primordial germ cells migrate–> from yolk sac to hind gut to developing gonad.
  • Proliferate by mitosis to become oogonia
  • Oogonia develop in clusters and then enter meiosis to develop into primary oocytes
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3
Q

What stimulates primordial follicles to develop into primary follicles?

A

Intra ovarian factors. NOT gonadotrophins

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4
Q

What initiates follicle recruitment?

A

FSH wave

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5
Q

Describe the key points of oestradiol production

A
  • Involves theca and granulosa layers
  • Main enzyme= Aromatase= converts testosterone to oestradiol
  • Stimulated by FSH and LH
  • Theca cells stimulated by LH produce testosterone, testosterone moves to the granulosa cells where it is converted into oestradiol
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6
Q

What stimulates the LH surge before ovulation occurs?

A

Oestradiol (and progesterone suppresses it)

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7
Q

When is meiosis 2 activated?

A

At fertilisation due to influx of calcium

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8
Q

How does the LH surge allow meiosis 1 to be completed?

A

LH surge removes meiotic inhibitors

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9
Q

Describe luteinisation

A
  • Basement membrane breaksdown
  • Granulosa cells hypertrophy= large luteal cell
  • Theca cells proliferate= small luteal cell
  • Intense angiogenesis
  • Steroidogenesis switches secretion from oestradiol to progesterone
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10
Q

What does the hormone Luteotroph do?

A

Support the growth/ function of the CL

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11
Q

What is StAR?

A
  • Steroid acute regulatory factor
  • It is a transport protein that regulated cholesterol transfer to the mitochondria
  • Rate limiting step in the production of steroid hormones
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12
Q

What does luteolysis enable?

A
  • Follicular development

- Return to oestrus

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13
Q

What is the key luteolytic hormone?

A

PGF2a

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14
Q

What is the counter current system of PGF2a in the ovary especially important in the sheep?

A
  • Because majority of PGF2a produced goes directly to the ovary via to ovarian artery to cause luteolysis.
  • In the sheep almost all of the PGF2a is denatured by one pass through the lungs, so it must be able to bypass general circulation.
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15
Q

Describe the mechanism of luteolysis incows

A

-Oxytocin released by the CL and posterior pituitary gland activated the oxytocin receptors in the endometrium of the uterus. Stimulates endometrium to release PGF2a which then acts n the CL to cause luteolysis and further release of oxytocin.

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