4 - Repro - Gamete development 2 Flashcards Preview

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Flashcards in 4 - Repro - Gamete development 2 Deck (38):
1

What causes oocytes to arrest in the Diplotene stage of prophase I?

Oocyte Maturation Inhibitor (OMI)
- from follicular cells

2

Which cells secrete Oocyte Maturation Inhibitor (OMI), and which stage of meiosis does this arrest oocytes in?

Follicular cells
Diplotene stage of prophase I

3

Why is there an increased risk of imperfect oocytes as a woman ages?

More time an oocyte is arrested in development
= increased risk of mutations

4

Approx how many oocytes are present when a woman reaches puberty?

~ 40,000

5

How many oocytes start to mature each month after a woman reaches puberty?

~ 15-20
only one fully matures each month

6

What are the 3 stages of oocyte maturation?

1) Pre-antral
2) Antral
3) Pre-ovulatory

7

What occurs in the pre-antral stage of oocyte maturation?

- Follicular cells change from simple squamous to stratified cuboidal granulosa cells
- Stromal cells form the theca folliculi (theca interna and theca externa)

8

Which cells form a fibrous capsule around the developing oocyte?

Theca externa

9

Which cells secrete the zona pellucida?

Granulosa cells

10

How are the granulosa cells and thecal cells arranged around the developing oocyte?

- Granulosa cells surround oocyte
- Thecal cells surround granulosa cells

11

What occurs in the antral stage of oocyte development?

- Granulosa cells proliferate and secrete fluid, forming the antrum
- Theca interna cells bind LH = stimulates androgen production
- Granulosa cells bind FSH = stimulates conversion of androgens to oestrogens

12

Which cells surrounding the oocyte bind LH?

Theca interna cells

13

Which cells surrounding the oocyte bind FSH?

Granulosa cells

14

Which cells surrounding the oocyte secrete androgens?

Theca interna cells

15

Which cells surrounding the oocyte convert androgens to oestrogens?

Granulosa cells

16

Name the 3 types of oestrogen in the female body:

- Oestriol
- Oestrone
- Oestradiol

17

Name the type of follicle produced in the antral stage of development:

Secondary/Graafian follicle

18

What is the precursor of the androgens and oestrogens produced in the ovary?

Cholesterol

19

When does a secondary/Graafian follicle enter the pre-ovulatory stage of development?

~ 37 hrs before ovulation

20

What occurs in the pre-ovulatory stage of oocyte maturation?

- LH receptors appear on granulosa cells, and are stimulated by the LH surge
- LH surge restarts meiosis I
- Oocyte arrests in Metaphase II ~ 3hrs before ovulation

21

In what stage of meiosis is an oocyte arrested in, in the pre-ovulatory stage of develoment?

Metaphase II

22

When is meiosis II of an oocyte completed?

Completed if the oocyte is fertilised

23

At ovulation, what is the size of the follicle?

~ 25 mm

24

What causes the follicle to rupture at ovulation?

LH surge
= increases collagenase activity

25

If an oocyte is fertilised at the ampula, how many days does it take for it to reach the uterine lumen?

~ 3-4 days

26

Which cells secrete progesterone?

Granulosa lutein cell (of the corpus luteum)

27

Name the 2 types of cells in the corpus luteum:

1) Granulosa lutein cells
2) Theca lutein cells

28

How long does the corpus luteum survive if the oocyte is not fertilised?

~ 14 days
Becomes corpus albicans (fibrotic scar tissue)

29

The change in which hormone precipitates menstrual bleeding?

Decrease in progesterone
- due to death of corpus luteum

30

What prevents the degradation of the corpus luteum if the oocyte is fertilised?

Developing embryo secrete hCG, which maintains the corpus luteum

31

If fertilisation occurs, for how long does the corpus luteum secrete progesterone?

until the 4th month of development, as placenta can then take over

32

Decribe the release of GnRH from the hypothalamus:

Pulsatile release ~ 1-3 hrs

33

Which G- protein does LH and FSH stimulate in the gonads? Therefore which enzyme is the effector?

Gs
Adenylyl cyclase

34

Which male hormone has a circadian rhythm?

Testosterone

35

Which cell secretes Androgen-binding globulin (ABG), to keep testosterone in the testes?

Sertoli cells

36

Which cells secrete inhibin?

Females = granulosa cells
Males = sertoli cells

37

Which hormone prevents oestrogen causing +ve feedback to the hypothalamus and anterior pituitary?

Progesterone

38

Which female hormone causes positive feedback to the hypothalamus and anterior pituitary, precipitating the LH surge?

Oestrogen (at high levels)
- at low levels it causes negative feedback