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MD3002 Physiology > Oogenesis and Follicular Development > Flashcards

Oogenesis and Follicular Development Flashcards

1
Q

Where does fertilisation occur?

A

Ampulla of the uterine tube

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2
Q

When does menarche usually occur?

A

11 - 13

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3
Q

What determines age at puberty?

A
  • Genetics
  • Nutrition
  • Geographic location
  • Exposure to light
  • Body composition, fat deposition
  • Exercise
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4
Q

Explain the ovarian cycle?

A
  • Follicular phase 15 days (range 9-23 days)
  • Ovulatory 1-3 days (and culminates with ovulation)
  • Luteal phase: 13 days (is less variable than follicular)
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5
Q

Explain the endometrial cycle?

A
  • Menstruation (day 1-4)
  • Proliferative pahse (day 4 - 14)
  • Secretory phase (day 14 - 28)
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6
Q

What are the functions of the ovary?

A
  • Oogenesis (production of gametes)
  • Maturation of oocyte
  • Expulsion of the mature oocyte (ovulation)
  • Secretion of female sex steroid hormones (oestrogen and progesterone) and peptide hormone inhibin
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7
Q

Describe the development of an oocyte and ovarian follicle? (what are the 5 stages / developments)

A
  • Primordial follicle
  • Primary folicle
  • Preantral follicle
  • Early antral follicle
  • Mature follicle (not clear-cut)
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8
Q

What cells line the outside of an oocyte?

A

Granulosa cells

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9
Q

What is the outside of the granulosa cells called?

A

The theca

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10
Q

What lies on the inside of a folicle?

A

oocyte

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11
Q

What is the name of the spce that lies inbetween granulosa cells as a result of them releasing fluid?

A

Antrum

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12
Q

What is the diameter of the mature folicle?

A

1.5 cm

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13
Q

Once the oocyte is released from the mature folicle what does it become?

A

Corpus luteum

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14
Q

What cells work together to produce oestrogen?

A

Theca and granulosa

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15
Q

When is meiosis II completed?

A

Fertilisation

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16
Q

What are oogonia produced by?

A

Mitotic division

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17
Q

When does the oogonia become a primary oocyte?

A

8-10 weeks gestation, prophase of 1st meiosis

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18
Q

How many oogonia are produced at the peak (8-10 weeks gestation)?

A

max 7 million

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19
Q

What are oogonia produced from?

A

Primordial germ cells

20
Q

What is meiosis?

A

Division of a germ cell involving two fissions of the nucleus and giving rise to four gametes, or sex cells, each possessing half the number of chromosomes of the original cell

21
Q

Describe the 1st phase of oogenesis?

A
  • Occurs during foetal life
  • Oogonia develop in the embryonic yolk sac 3 weeks post conception (pc)
  • Migrate to ovary
  • Colonise the cortex
  • Undergo mitosis
  • At 8 - 10 wks meiosis begins
22
Q

How many oocytes degenerate around birth?

A

1 - 2 MILLION

23
Q

How many oocytes degenerate around puberty?

A

400,000 around puberty

24
Q

At what stage are the remianing oocytes arrested at?

A

Meiotic prophase I

25
Q

What is the most common cytogenic abnormality which increases with maternal age?

A

Aneuploidy - down syndrome

26
Q

By how much do the chances of down syndrome increase from 15 to 45 years old?

A
  • 2 per 1000 at 15
  • 53.7 per 1000 at 45
    increases exponentially
27
Q

What is the resumption of meiosis stimulated by?

A

LH

28
Q

How does the cell divide in the first division of meiosis?

A

Cytoplasm is unequally shared forming a large secondary oocyte and a polar body (PB has no further role)

29
Q

When is meiosis arrested again?

A

Metaphase II

- Secondary oocyte is ovulated and 2nd division of meiosis is only completed in those oocytes that are fertilised

30
Q

How many mature ovum(s) are produced from meiotic divisions of an oocyte?

A

1 (4 mature spermatazoa in males)

31
Q

What is the thick layer of material between the oocyte and granulosa cells called?

A

Zona pellucida

32
Q

How are nutrients and chemical messangers passed to the oocyte?

A

Through cytoplasmic processes which form gap junctions which cross the zona pelucida

33
Q

What do follicular cells secrete and what can it be used to measure?

A

Anti-Mullerian hormone (AMH): levels reflect the ovarian follicular reserve and therefore can be measured to assess ovarian ageing

34
Q

What are the most numerous follicles at any time?

A

Small (primordial) follicles

35
Q

How many primary follicles can be lost per cycle?

A

650

36
Q

How many days/cycles does it take to reach 3 layers of follicular cells?

A

85 days (3 cycles)

37
Q

What hormone stimulates the rapid development of medium follicle over 14 days?

A

FSH

38
Q

What LH activate the theca interna to do?

A

LH activates the theca interna to synthesise androstenedione, the precursor for estradiol 17Beta synthesis by granulosa cells

39
Q

What is the corona radiata?

A

Layer of granulosa cells which cover the ovum after ovulation

40
Q

What does the corpus luteum become?

A

The corpus albicans

41
Q

What does the LH surge induce?

A

The prostaglandin endoperoxidase synthase in granulosa cells (sets up pseudoinflammatory response)

42
Q

What hormone stimulates the release of plasminogen activator from granulosa cells (converts plasminogen to plasmin)?

A

FSH (some LH)

43
Q

What do prostaglandins E and F do?

A

Release lysosomal enzymes that digest follicular wall -not completely understood

44
Q

What is a ‘stigma’?

A
  • Forms on surface of follicle, balloons out, forms vesicle and ruptures - oocyte expelled
  • Process facilitated by intracellular pressure and contraction of smooth muscle in theca
45
Q

Explain corpus luteum formation?

A

Mature follicle discharges its antral fluid and egg
- Collapses around antrum and undergoes rapid transformation
Granulosa cells enlarge and form gland-like structures ie CORPUS LUTEUM

46
Q

What does the corpus luteum secrete?

A
  • Oestrogen
  • Progesterone
  • Inhibin
47
Q

If no egg fertilisation, when does CL development reach maximum?

A

approx 10 days

- rapidly degenerates by apoptosis

MD3002 Physiology (24 decks)

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