The Menstrual Cycle

Question 1

T/F Duration of menstrual cycle is variable.

Answer 1

T 24-35 days

Question 2

Duration of bleeding during menstrual cycle

Answer 2

<8 days

Question 3

The two halves of the menstrual cycle are separated by what event?

Answer 3

ovulation

Question 4

Which half of the menstrual cycle is variable in length?

Answer 4

follicular/proliferative stage –> development of follicle in ovary and proliferation of uterine lining

Question 5

HPG axis

Answer 5

Hypothalamic GnRH –> Pituitary FSH and LH –> Ovarian estradiol and progesterone –> uterus

Question 6

T/F GnRH has a long half life.

Answer 6

F –> short –> short travel path ensures that hormone is only useful at the nearby pituitary

Question 7

T/F GnRH is released constitutively.

Answer 7

F –> pulsatile fashion –> frequency affects events (e.g. follicular phase = 60-90 min@low amp, luteal phase = 3-5 hours @high amp)

Question 8

T/F gonadotropic hormones share the same beta subunit.

Answer 8

F –> same alpha subunit between FSH, LH, hCG, TSH but different beta subunits

Question 9

T/F early development of follicles till secondary follicle stage is hormone independent

Answer 9

T –> only after puberty FSH can you have follicles growing beyond secondary follicle stage

Question 10

By what day is a follicle selected to be dominant

Answer 10

8

Question 11

At the beginning of the menstrual cycle there is a rise in ______ leading to recruitment of follicles.

Answer 11

FSH

Question 12

3 functions of FSH

Answer 12

stimulates granulosa cell proliferation, stimulation of aromatase activity in granulosa cells (conversion of androgen to estrogen), and up regulation of LH/FSH receptors

Question 13

Serum estradiol concentrations rise after stimulation by ____ and peak 1 day before ____.

Answer 13

FSH and ovulation

Question 14

_____ results in negative feedback on pituitary and hypothalamus, reducing FSH levels.

Answer 14

estrogen

Question 15

Once estradiol reaches a threshold estrogen feedback becomes stimulatory and results in increase in GnRH pulse frequency which increases ____

Answer 15

LH (and reexcites some FSH as well though not to original peak levels)

Question 16

3 functions of LH

Answer 16

causes release of oocyte from follicle 36 hours after surge, leads to luteinization of granulosa cells and increased progesterone production, resumption of meiosis of oocyte and release of 1st polar body

Question 17

In the ____ phase, estrogen and progesterone suppress gonadotropin release.

Answer 17

luteal

Question 18

____ promotes growth and reconstruction of endometrium.

Answer 18

estrogen –> glands lined by low columnar epithelia and mitoses become prominent

Question 19

effects of progesterone on uterus

Answer 19

limits growth, mitosis, DNA synthesis; increased tortuosity of glands/intensified coiling of spiral vessels, secretion of peptides and glycoproteins

Question 20

The corpus luteum dgenerates after ___ days

Answer 20

14

Question 21

Withdrawal of progesterone causes ___ endometrium to slough.

Answer 21

secreory

Question 22

Why does FSH increase at the end of the cycle?

Answer 22

no more progesterone/estrogen negative feedback

Question 23

If fertilization occurs, embryo begins making ___

Answer 23

hCG –> maintains corpus luteum

Question 24

T/F progesterone and estrogen are continued to be secreted if there is fertilization

Answer 24

T

Question 25

The parallel regulatory system for menstrual cycle involves what proteins?

Answer 25

activin and inhibin (TGF family)

Question 26

functions of inhibin

Answer 26

reduce FSH synthesis, reduce pituitary gnrh receptors, increase LH receptors on theca cells

Question 27

____ has one alpha and one beta subunit

Answer 27

inhibin

Question 28

inhibin is produced by what cells?

Answer 28

granulosa

Question 29

where is activin produced?

Answer 29

gonads and pituitary

Question 30

functions of activin

Answer 30

enhance gnrh activity in pituitary and promotes granulosa proliferation/fsh receptors in follicle