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BMSc Repro > Oogenesis, ovulation and corpus luteum > Flashcards

Oogenesis, ovulation and corpus luteum Flashcards

1
Q

What is oogenesis

A

Formation and development of the female gamete from undifferentiated germ cell to highly differentiated oocyte ready to be fertilised

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2
Q

When does oogenesis begin and end

A

Begins in foetal life and ends with fertilisation.

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3
Q

Where do the primordial follicles sit in the ovaries?

A

They sit within the ovarian cortex.

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4
Q

Describe the maturity of the following cumulus cells:
1. expanded cumulus cells
2. unexpanded cumulus cells

A
  1. Mature oocyte
  2. Immature oocyte

(however, all eggs will still be fertilised)

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5
Q

What is a germinal vescile?

A

The term germinal vesicle describes the nucelus of an oocyte that is arrested in prophase I. Once germinal vescile breakdown occurs meiosis I can be completed and will result in the first polar body formation,

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6
Q

How mature is the oocyte if you can see the germinal vescile?

A

Immature

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7
Q

How mature is the oocyte if you cannot see the germinal vesicle but no polar body is present?

A

Assume the oocyte is undergoing meiosis I

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8
Q

How mature is the oocyte if there is a polar body present?

A

Fully mature, the oocyte is ready for fertilisation to help complete meiosis II.

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9
Q

Should an IVF collected oocyte be thrown away if it’s too small or too large?

A

> 200 um oocytes should be thrown away as its either the fusion of two cells or it contains too much cytoplasm and therefore DNA from a polar body

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10
Q

Which out of the following oocyte dimorphisms should be discarded?
- cytoplasm granularity
-vacuoles
- Smooth endoplasmic reticulum discs

A

Smooth endoplasmic reticulum discs

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11
Q

What name is given to the primordial germ cells when they arrive at the genital ridges

A

Oogonia (gonocytes)

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12
Q

When do the oogonia start meiosis?

A

when the pre-granulosa cells surround them

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13
Q

When are oogonia called primary oocytes

A

When they enter meiosis

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14
Q

When is the first stage that germs cells are lost in the developing ovary

A

Before birth, when connections break down between primary oocytes

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15
Q

Describe a primordial follicle

A

A primary oocyte surrounded by a thin layer of pre-granulosa cells

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16
Q

How do we describe ovarian reserve?

A

quiescent primordial follciles

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17
Q

How often are primordial follicles activated?

A

A handful every day

18
Q

What is the difference between a primordial follicle and a primary follicle

A

Primordial contains a thin layer of pre-granulosa cells surrounding the primary oocyte.

Primary follicles contain a cuboidal layer of granulosa cells surrounding the primary oocyte

19
Q

Describe a secondary follicle

A

Primary oocyte surrounded by 2 layers of cuboidal granulosa cells

20
Q

What happens to the secondary follicle before puberty?

A

They undergo atresia due to lack of hormone stimulation

21
Q

What causes the secondary follicle to develop into an antral follicle

A

FSH

22
Q

At what stage does the ZP form and the ability to cytodifferentiation is acquired?

A

Development from primary follicle to secondary follicle

23
Q

How long does the phase of development from primary follicle to secondary follicle last?

A

120 days

24
Q

Describe how the antrum appears

A

small cavities appear between granulosa cells and then they coalese to form the follicular antrum

25
Q

What are mural granulosa cells

A

Granulosa cells that sit around the edge of the antrum

26
Q

What are cumulus oophorus cells?

A

Granulosa cell stalk that the oocyte is attached too

27
Q

At what stages of the oocyte DNA nucleus start to become less active and compacts

A

At the antral phase

28
Q

How long does the antral phase last?

A

8-12 days

29
Q

Describe the 2 somatic layers surrounding the follicle at the antral stage

A
  • Theca externa - vascular layer
  • Theca interna - thick fibrotic layer
30
Q

Which receptors are present on theca interna cells?

And what hormone production do they stimulate?

A

LH

Cholesterol to Androgens

31
Q

Which receptors are present on granulosa cells during antral follicle stage?

And what hormone production do they stimulate?

A

FSH

Androgens to oestrogen

32
Q

Which hormones stimulate granulosa cells to grow at antral follicle stage?

A

Androgens and oestrogen

(as well as FSH and LH)

33
Q

At what point are there also LH receptors on granulosa cells?

A

When there are high levels of LH

34
Q

Describe the selection of the dominant (graafian) follicle

A

The most mature follicle develops LH receptors on the granulosa cells so when FSH levels drop, this follicle can rely on this to still recieve hormonal input to grow. Whereas the rest can’t and so die off

35
Q

Describe other features of adaptation that help graafian follicle to survive in the FSH drop:

A

Dominant follicle more fit to cope with declining FSH levels
- high FSH receptor levels
- increased vascularity in the theca layer (preferential delivery of FSH to this follicle)
- LH receptor in granulosa cells

36
Q

Does oestrogen or progesterone increase the frequency of GnRH pulses

A

Oestrogen increases
Progesterone decreases

37
Q

Does high frequency GnRH pulses stimulate the release of LH or FSH

A

LH

38
Q

What effect does the LH surge have on the oocyte and the follicle?

A
  • ovulation
  • final maturation of the oocyte (via progesterone also) - DNA condensation
  • differentiation of theca and granulosa cells to luteal cells (lutinisation)
39
Q

What do theca cells secrete

A

progesterone

40
Q

At what point is an oocyte called secondary oocyte

A

Once it has completed the first meiotic division and has produced a polar body

41
Q

What enzymes help with ovulation?

A

Matrix metalloproteinases digest proteins to make the surface of the ovary thin

BMSc Repro (9 decks)

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