33 Female reproduction

Question 1

Give a brief account of the ovarian cycle with the name of the 3 phases.

Answer 1

1. Follicular phase
   - dominant ovarian follicle develops and secretes estrogen under FSH and LH stimulation
2. Ovulation
   - positive feedback of estrogen induces LH surge
3. Luteal phase
   - corpus luteum produces progesterone and estrogen with the support of LH

Question 2

Follicular/ Luteal phase is more or less constant.

Answer 2

Luteal (14 days)

Question 3

When does the secretory phase occur? Which phase is it equivalent to?

Answer 3

= luteal phase;
occurs after ovulation, enrichment of blood supply and glandular secretion of nutrients prepare the endometrium to receive embryo

Question 4

Describe the hypothalamic-pituitary-ovarian axis.

Answer 4

1. Trophic stimulation
   - hypothalamic kisspeptin > stimulates GnRH release from the hypothalamus
   > anterior pituitary release FSH and LH

Question 5

State the 3 structures that involved in the feedback controls in the hypothalamic-pituitary-ovarian axis and briefly mention what and how.

Answer 5

1. Ovarian follicles: estradiol, inhibin B (granulosa cells)
   [negative feedback]
2. Dominant follicle: high estradiol (estrogen) [positive feedback]
3. Corpus luteum: progesterone, estradiol, inhibin A (luteal cells) [negative feedback]

Question 6

_____ stimulates ______ cells to synthesize androgens, which diffuse across the basement membrane into granulosa cells.
_______ induces the expression of aromatase enzyme in granulosa cells to convert androgen precursors from theca cells into forming estrogens

Answer 6

LH; theca cells;
FSH

please refer to picture in lecture 33 notes!

Question 7

As follicle matures, ________ induces the expression of LH receptors on granulosa cells, which start producing a small amount of ______________ in response to LH.

Answer 7

FSH;

progesterone

Question 8

Ruptured follicle after ovulation transformed into corpus luteum under the action of?

Answer 8

LH

Question 9

Under the supporting action of LH, luteal cells of corpus luteum produce?

Answer 9

Progesterone and estrogen

Question 10

Which of the following is true?
A. peak of progesterone secretion in mid-luteal phase is attained by basement membrane separating the theca cells and granulosa cells breaks down, and the luteinized granulosa cells have free access to circulating LDL-cholesterol in blood
B. corpus luteum is programmed to work for 14 days and will undergo apoptosis

Answer 10

Both

Question 11

During pregnancy, _____________ will be secreted, which is a LH-like hormone.

Answer 11

human chorionic gonadotrophin (HcG)

Question 12

State the negative feedback mechanisms of inhibin and progesterone respectively.

Answer 12

Inhibin: from corpus luteum, negative feedback on FSH from the anterior pituitary only.

Progesterone: from corpus luteum, negative feedback on both LH and FSH from the anterior pituitary.

Question 13

How is selection (dominance vs atresia) done in follicles?

Answer 13

1. dominant follicle will respond to FSH stimulation with high expression of aromatase activity for estrogen synthesis
2. FSH and estrogen stimulate granulosa cell proliferation > accelerated growth of the dominant follicle (with more blood flow to receive higher absolute supply of FSH)
3. increase circulating levels of estradiol from the dominant follicle eventually suppresses FSH secretion, remaining follicles cannot develop > atresia

Question 14

How does mid-cycle LH surge occur?

Answer 14

High level of estrogen is produced by the dominant follicle > switches from exerting a negative feedback to positive feedback on the hypothalamus-anterior pituitary in triggering massive secretion of gonadotrophins (FSH and LH)

Question 15

What are the effects of LH surge?

Answer 15

1. triggers resumption and completion of first meiotic division of the primary oocyte.
2. induces ovulation
3. induces luteinization of the ruptured follicle to become a corpus luteum

Question 16

Summary of FSH effects.

Answer 16

1. recruitment of follicles for follicle development
2. induce aromatase enzyme in granulosa cells for estrogen synthesis.
3. stimulate granulosa cell proliferation, hence follicular growth (together with estrogen)

Question 17

Summary of estrogen effects.

Answer 17

1. Early to mid-follicular phase: estrogen produced by dominant follicle plays an important role in its selection to achieve dominance
2. Late follicular phase: estrogen provides a positive feedback control to induce LH surge.

Question 18

Summary of LH effects.

Answer 18

1. Stimulate androgen production by theca cells for conversion of estrogen in granulosa cells (for estrogen synthesis)
2. Mid-cycle LH surge: induces ovulation and luteinization of the ruptured follicle to form corpus luteum.

Question 19

Corpus luteum secretes _____________ and ___________ under the stimulation of _______.

Answer 19

progesterone and estrogen;

LH

Question 20

Which of the following is/ are true?
A. Progesterone and estrogen reach a peak at around mid-luteal phase to prepare the endometrium to achieve optimal receptivity for implantation
B. When pregnancy fails to occur, corpus luteum undergoes degeneration
C. Menstruation = withdrawal of progesterone and estrogen
D. 3 days is needed for oocyte to move to the endometrial lining for implantation

Answer 20

All except D

6-7 days!

Question 21

Follicles in early phase secretes low amounts of ________ and ________, which has negative feedback on _________.

Answer 21

estrogen and inhibin;

FSH

Question 22

Which of the following is/are false?

A. All oogonia enter into meiosis to become secondary oocytes, and are arrested at the diplotene stage of the first meiotic division
B. Resumption of first meiotic division occurs at the time of ovulation triggered by the LH surge, forming secondary oocyte and 1st polar body
C. The 2nd polar body is formed only when fertilization occurs
D. - Fusion of pronuclei from the ootid and sperm restores the zygote to diploid state

Answer 22

A. should be primary oocytes

C is correct! The second meiotic division is triggered to complete at the time of fertilization with the expulsion of the 2nd polar body and the formation of ootid

Question 23

Which of the following are estrogenic effects on female reproductive tract (in follicular phase)?

A. increase secretion and fluidity of cervical mucus
B. increase motility of fallopian tube and uterus
C. stimulate stromal and ductular growth of the mammary gland
D. stimulate enlargement and pigmentation of the areola
E. decrease HDL, increase LDL
F. stimulate pubertal growth spurt and bone mineralization
G. protect bone from resorption and loss

Answer 23

All except E

should be increase HDL, decrease LDL

Question 24

Which of the following is/are not effects of progesterone?
A. Prepare optimal receptivity of the endometrium for implantation
B. stimulate mobility of uterus
C. Decrease cervical mucus thickness
D. Stimulate lobulo-alveolar growth of the mammary gland

Answer 24

B

should be decrease, for successful implantation

Question 25

State the 4 approaches of ovulation.

Answer 25

1. preovulatory rise in plasma estrogen (to provide positive feedback signal to induce LH surge)
2. Preovulatory LH surge (to trigger ovulation and luteinization of the follicle to form the corpus luteum)
3. Peak day symptoms of cervical mucus (representing the effect of preovulatory rise in estrogen)
4. Ultrasongraphic imaging of preovulatory follicle (18-20mm)

Question 26

State the 2 ways to know ovulation has taken place.

Answer 26

1. Postovulatory rise in plasma progesterone (produced by corpus luteum)
2. Postovulatory rise in basal body temperature by 0.3-0.5 degrees (representing pyrogenic effect of progesterone)

Question 27

How does cervical mucus change under the effect of estrogen?

Answer 27

1. increase in volume
2. increase in fluidity
3. increase in stretchability
4. increase in pH
5. ferning pattern (due to increased salt content, growing of salt crystals)