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Repro > 1.2 - Origin of the gametes - females > Flashcards

1.2 - Origin of the gametes - females Flashcards

1
Q

what does gamete production involve?

A

proliferation of germ cells by mitosis

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2
Q

what happens after proliferation of germ cells by mitosis?

A

genetic reshuffling & reduction to haploid meiosis

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3
Q

what has to happen to form mature gamete?

A

cyto-differentiation (development of specialised structures and functions in embryonic cells)

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4
Q

where do the female primordial germ cells colonise?

A

in the cortex of the primordial gonad becoming oogonia

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5
Q

how do oogonia proliferate?

A

rapidly by mitosis

7million by 20 weeks

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6
Q

what happens to the 7 million oogonia in the cortex of primordial gonad?

A

most die during gestation, leaving about 2 million

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7
Q

what happens to the 2 million oogonia which survive gestation in the cortex of primordial gonad?

A

begin meiosis before birth

becoming primary oocytes (egg cells)

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8
Q

what is entry into meiosis 1 stimulated by?

A

mesonephric cells

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9
Q

what are mesonephric cells?

A

flattened epithelial cells called follicle cells

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10
Q

what do follicle cells surround? forming?

A

the primary oocytes to form primordial follicles

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11
Q

when does meiosis arrest?

A

at the diplotene stage (resting stage) of prophase

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12
Q

why does meiosis arrest at the diplotene stage of prophase?

A

due to oocyte maturation inhibitor (OMI) from follicular cells

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13
Q

what is the primordial follicle?

A

primary oocyte surrounded by the follicular cells

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14
Q

when does a woman have all the oocytes she will ever have?

A

at birth

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15
Q

where are all ova produced from?

A

the ‘stock’ of oocytes the woman has at birth - no more can be formed later (in terms of oocytes)

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16
Q

what does meiosis arresting at diplotene stage of prophase increase the chance of?

A

cell damage

increasing risk of fetal chromosomal abnormalities in pregnancies of older women

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17
Q

what happens at puberty until menopause about 40 years later?

A

a small number of follicles begin further development each day (not oocyte - what the follicles surround)

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18
Q

what are the stages a follicle requires to go through before forming a mature gamete?

A
  1. pre-antral / primordial follicle
  2. antral follicle (Graafian / vesicular follicle)
  3. pre-ovulatory follicle
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19
Q

what happens to the primary oocyte in primordial to pre-antral (1st stage)?

A

the primary oocyte grows dramatically, but doesn’t re-start meiosis

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20
Q

what happens to the follicular cells in primordial to pre-antral (1st stage)?

A

change from flat to cuboidal cells

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21
Q

what happens to the cuboidal cells (from flat) in primordial to pre-antral (1st stage)? called?

A

proliferate to form multiple layered epithelium - granulosa cells

22
Q

what is the granulosa cells’ function?

A

to secrete glycoprotein to surround the primary oocyte with a zona pellucida

23
Q

what do surrounding stromal (connective tissue) cells form?

A

a theca folliculi with 2 parts

24
Q

what are the 2 parts of the theca folliculi?

A

inner: theca interna (vascular and endocrine)
outer: theca externa (fibrous & capsule)

25
Q

what secretes oestrogen?

A

theca and granulosa cells collaborate to secrete oestrogens

26
Q

what happens to the granulosa cells in antral transition?

A

continue to proliferate, fluid appears between them, eventually forming an antrum

27
Q

what happens as more fluid forms between the granulosa cells in antral transition?

A

secondary / Graafian follicle (2nd (antral) stage) expands dramatically

28
Q

in humans, antral follicles expand to what size? under what stimulation?

A

2mm diameter

withOUT stimulation by reproductive hormones

29
Q

what does continued development of Graafian follicle depend upon?

A

follicle stimulating hormone (FSH)

30
Q

how does FSH function?

A

binds ONLY to granulosa cells of lutinising hormong (LH)

which binds ONLY to thecal cells (formed from surrounding stroma)

31
Q

in each cycle, what happens to the follicles?

A

usually, only 1 follicle becomes dominant and develops further

32
Q

how does the dominant follicle develop? (under what stimulation)

A
  1. under the influence of LH, thecal cells secrete androgens
  2. androgens converted to oestrogens by granulosa cells under influence of FSH
    (FSH –(bind)–> granulosa cells of LH –(bind)–> thecal cells –(secrete)–> androgens–(converted)–> oestrogen)
33
Q

when does the pre-ovulatory follicle phase begin? stimulated by?

A

37 hours before ovulation

under the influence of oestrogen

34
Q

where do receptors for LH appear?

A

on the outer granulosa cells

35
Q

what is the pre-ovulatory follicle –> ovulation stimulated by?

A

an LH surge

leading to rapid changes in the follicle

36
Q

what happens within 3 hours of LH surge?

A

oocyte re-starts meiosis - 1st meiotic division is completed

37
Q

how can one describe the division of the completed first meiotic division?

A

asymmetric: cytoplasm remains with 1 daughter

the other forms a condensed polar body

38
Q

what happens to the secondary follicle? (in pre-ovulatory follicle stage - 3rd)

A

enters meiosis II and then arrests again 3 hours prior to ovulation

39
Q

when does follicle size increases dramatically? what happens to the structure?

A

by increase in antral fluid volume (full size being 25mm) and the structure begins to weaken

40
Q

what does LH stimulate in pre-ovulatory stage?

A

stimulates collagenase activity, leading to follicle rupture

41
Q

what happens to the ovum in pre-ovulatory stage after LH has stimulated collagenase leading to follicle rupture??

A

the ovum (egg) is carried out in the fluid and gathered up into the fallopian tube by fimbria

42
Q

when is meiosis completed?

A

when the ovum is fertilised

43
Q

what happens to unfertilised cells?

A

degenerate 24 hours after ovulation

44
Q

what happens to the remains of the follicle after ovulation?

A

re-organise themselves into a corpus luteum

45
Q

what does corpus luteum secrete? influenced by what?

A

progesterone and oestrogen

under influence of LH

46
Q

how long does corpus luteum live for before regressing?

A

14 days before regressing spontaneously (in absence of a fertilised ovum)

47
Q

what are the early antral to corpus luteum stages synchronised with?

A

the reproductive cycle of female

48
Q

what happens in the menstrual cycle of humans?

A

the lining of the uterus is shed between cycles as a menstrual bleed

49
Q

when does rapid antral development begin?

A

towards the end of menstruation, culminating in ovulation about 10 days later (12-14 days after onset of menstrual bleed)

50
Q

what happens to the corpus luteum in the absence of pregnancy?

A

present for 14 days before it regresses and a new menstrual bleed begins

51
Q

what is the ovarian cycle?

A

the pattern of ovarian changes during the menstrual cycle

Repro (78 decks)

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