Female Repro

Question 1

What happens in ovulation and what hormone stimulates it?

Answer 1

Oocyte released from a follicle

LH stimulates it

Question 2

What determines sex of embryo?

Answer 2

Sperm as can contribute X or Y

Question 3

What happens during the secretory phase?

Answer 3

1) Corpus luteum releases progesterone

2) Endometrium generates blood vessels and proteins needed for implantation of a fertilised embryo

Question 4

What happens in the proliferative phase?

Answer 4

Endometrium rapidly grows under influence of oestrogen

Question 5

What is capacitation?

Answer 5

Final stage of sperm maturation in female genitalia (Unable for sperm to fertilise beforehand)

Question 6

What does the corpus luteum degenerate into?

Answer 6

Corpus Albicans

Question 7

Define block to polyspermy

Answer 7

Egg prevents further sperm fertilising it, after fertilisation

Question 8

What helps to ensure “block to polyspermy” occurs?

Answer 8

1) Egg releases secretory vesicle contents by exocytosis

2) Enzymes from Vesicles –> Zona Pellucida, inactivating sperm binding sites and hardening the zona pellucida

Question 9

What hormone does the hypothalamus release to stimulate release of gonadotrophins?

Answer 9

GnRH (Gonadotrophin releasing hormone)

Question 10

What function does GnRH have?

Answer 10

Acts on APG stimulating it to release FSH and LH

Question 11

What cells does FSH react on in each sex?

Answer 11

M: Sertoli Cells
F: Granulosa Cells

Question 12

What cells does LH act on in each sex?

Answer 12

M: Leydig Cells
F: Theca Cells

Question 13

What do Sertoli cells do?

Answer 13

Release MIF, inhibin and activins (Regulate FSH secretion) and androgen binding protein (Increase testosterone conc)

Question 14

What do Granulosa cells do?

Answer 14

Convert androgens into oestrogen using aromatase enzyme

Question 15

What do Theca cells do?

Answer 15

Production of androgens (Oestrogen Precursors) that diffuse into granulosa cells to form oestrogen

Question 16

What happens in oogensis?

Answer 16

1) Oogonia undergo mitotic division in utero
2) Oogonia develop into primary oocytes and begin meiotic division by replicating their DNA (Meiotic Arrest)
a) Puberty: Renewed activity in the ovaries and oocytes for ovulation undergo meiosis
b) Meiosis 2 occurs if secondary oocyte fertilised –> Ovum

Question 17

How many secondary oocytes does each primary oocyte yield?

Answer 17

1 Secondary oocyte

1 Non-Functional Polar Body

Question 18

Why is there only one primary oocyte yield by secondary oocyte?

Answer 18

Only one ovum can be yielded per primary oocyte

Secondary oocyte divides into one ovum and a second polar body.

Question 19

What are the 2 phases of the menstrual cycle?

Answer 19

1) Follicular Phase

2) Luteal Phase

Question 20

MC: What takes place in follicular phase

Answer 20

Mature follicle and secondary oocyte develop

Question 21

MC: What takes place in the luteal phase?

Answer 21

Takes place after ovulation until corpus luteum death

Question 22

MC: What causes oestrogen levels to rise in the follicular phase?

Answer 22

Oestrogen released from the granulosa cells and from developing/dominant follicle

Question 23

MC: What is the effect of oestrogen at low levels on Gonadotrophins?

Answer 23

At low levels oestrogen inhibits gonadotrophin release

Question 24

MC: Effect of decreasing FSH in the follicular phase?

Answer 24

Decreasing FSH levels causes non-dominant immature follicles to degenerate

Question 25

MC: Effect of oestrogen at high levels on gonadotrophins?

Answer 25

Exerts positive feedback on gonadotrophin secretion, stimulating LH surge

Question 26

MC: Effect of LH surge?

Answer 26

Stimulation of Ovulation

Question 27

MC: Why is there an increase in Progesterone and Oestrogen levels following ovulation?

Answer 27

Ruptured follicle--> Corpus Luteum, thereby releasing large amounts of progesterone and oestrogen

Question 28

MC: Why do LH and FSH levels decrease after ovulation?

Answer 28

Inhibited by high progesterone and oestrogen concentrations

Question 29

Why is important for low LH concentration in Luteal phase

Answer 29

Low but adequate LH can act to maintain corpus luteum

Question 30

What makes oestrogen and progesterone concentration levels fall towards end of luteal phase?

Answer 30

1) Corpus Luteum degenerates into corpus albicans if fertilisation doesn't occur 2) Progesterone and oestrogen then no longer released

Question 31

Why does FSH levels increase at end of cycle?

Answer 31

Fall in progesterone and oestrogen concentration means FSH no longer inhibited So its plasma conc can rise

Question 32

Why does Corpus Luteum not degenerate if fertilisation occur?

Answer 32

When blastocyst implants, invading trophoblast cells release hCG. This acts to maintain corpus luteum throughout pregnancy.