4 - Repro - Gamete development 2

Question 1

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

Answer 1

Oocyte Maturation Inhibitor (OMI)

- from follicular cells

Question 2

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

Answer 2

Follicular cells

Diplotene stage of prophase I

Question 3

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

Answer 3

More time an oocyte is arrested in development

= increased risk of mutations

Question 4

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

Answer 4

~ 40,000

Question 5

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

Answer 5

~ 15-20

only one fully matures each month

Question 6

What are the 3 stages of oocyte maturation?

Answer 6

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

Question 7

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

Answer 7

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

Question 8

Which cells form a fibrous capsule around the developing oocyte?

Answer 8

Theca externa

Question 9

Which cells secrete the zona pellucida?

Answer 9

Granulosa cells

Question 10

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

Answer 10

• Granulosa cells surround oocyte

- Thecal cells surround granulosa cells

Question 11

What occurs in the antral stage of oocyte development?

Answer 11

• 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

Question 12

Which cells surrounding the oocyte bind LH?

Answer 12

Theca interna cells

Question 13

Which cells surrounding the oocyte bind FSH?

Answer 13

Granulosa cells

Question 14

Which cells surrounding the oocyte secrete androgens?

Answer 14

Theca interna cells

Question 15

Which cells surrounding the oocyte convert androgens to oestrogens?

Answer 15

Granulosa cells

Question 16

Name the 3 types of oestrogen in the female body:

Answer 16

• Oestriol
• Oestrone
• Oestradiol

Question 17

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

Answer 17

Secondary/Graafian follicle

Question 18

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

Answer 18

Cholesterol

Question 19

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

Answer 19

~ 37 hrs before ovulation

Question 20

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

Answer 20

• 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

Question 21

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

Answer 21

Metaphase II

Question 22

When is meiosis II of an oocyte completed?

Answer 22

Completed if the oocyte is fertilised

Question 23

At ovulation, what is the size of the follicle?

Answer 23

~ 25 mm

Question 24

What causes the follicle to rupture at ovulation?

Answer 24

LH surge

= increases collagenase activity

Question 25

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

Answer 25

~ 3-4 days

Question 26

Which cells secrete progesterone?

Answer 26

Granulosa lutein cell (of the corpus luteum)

Question 27

Name the 2 types of cells in the corpus luteum:

Answer 27

1) Granulosa lutein cells | 2) Theca lutein cells

Question 28

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

Answer 28

~ 14 days | Becomes corpus albicans (fibrotic scar tissue)

Question 29

The change in which hormone precipitates menstrual bleeding?

Answer 29

Decrease in progesterone | - due to death of corpus luteum

Question 30

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

Answer 30

Developing embryo secrete hCG, which maintains the corpus luteum

Question 31

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

Answer 31

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

Question 32

Decribe the release of GnRH from the hypothalamus:

Answer 32

Pulsatile release ~ 1-3 hrs

Question 33

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

Answer 33

Gs | Adenylyl cyclase

Question 34

Which male hormone has a circadian rhythm?

Answer 34

Testosterone

Question 35

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

Answer 35

Sertoli cells

Question 36

Which cells secrete inhibin?

Answer 36

``` Females = granulosa cells Males = sertoli cells ```

Question 37

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

Answer 37

Progesterone

Question 38

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

Answer 38

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