hormonal control of the menstrual cycle

Question 1

describe the pattern of FSH

Answer 1

Increases in early part of follicular phase, then steadily decreases throughout
remainder of cycle EXCEPT small midcycle peak

Question 2

describe the pattern of LH

Answer 2

Constant during most of follicular phase, then large midcycle increase (LH surge)
peaking ~18h before ovula?on. Then rapid decrease with further slow decline
during the luteal phase.

Question 3

describe the pattern of oestrogen

Answer 3

Low and stable for 1st week, increases rapidly in 2nd weeks, starts to decline before
LH peak. Then second increase due to corpus luteum in last few days of cycle.

Question 4

describe the pattern of progesterone

Answer 4

Low level due to ovary release during follicular phase with small increase just
before ovula?on. Soon a[er ovula?on, large increase due to CL release, then
similar paPern to oestrogen.

Question 5

describe the pattern of inhibin

Answer 5

similar to oestrogen

Question 6

what does low concentration oestrogen inhibit

Answer 6

FSH and LH

Question 7

what does inhibin do

Answer 7

inhibits secretion of FSH

Question 8

what does a dramatic increase in oestrogen do

Answer 8

increases LH and FSH causing positive feedback of the LH surge which triggers ovulation

Question 9

what does high progesterone in the presence of oestrogen do

Answer 9

inhibits FSH and LH during the luteal phase and pregnancy

Question 10

what cells express receptors for FSH during the follicular phase of the menstrual cycle

Answer 10

granulosa cells

homologous to sertoli cells

Question 11

what is the function of FSH

Answer 11

max conc during follicular phase

stimulates growth of medium sized follicles

Question 12

what is the function of LH

Answer 12

stimulates steroid hormone synthesis by the corpus luteum

stimulates ovulation

Question 13

what stimulates an increase in LH

Answer 13

increase in oestrodiol 17b (oestrogen) which is secreted by the dominant follicle

Question 14

what cells are homologous to theca cells

Answer 14

Leydig

because they both synthesise androgens

Question 15

what do theca cells do

Answer 15

synthesise androgens which are then converted to estrogens by granulosa cells in the follicle by diffusing across the basement membrane

Question 16

what hormone stimulates granulosa cells to convert androstenedione to oestrodiol 17b

Answer 16

FSH

Question 17

What causes the LH surge

Answer 17

dominant follicle secretes large amount of oestrogen which stimulates LH surge
this triggers ovulation of corpus luteum
mediated by granulosa cells

Question 18

what are the effects of LH on the ovary

Answer 18

primary oocyte completes first meiotic division and undergoes cytoplasmic changes

antrum size and blood flow increased

granulosa cells release progesterone and decrease oestrogen

enzymes and prostaglandins break down the follicular membrane which rupture

corpus luteum forms

Question 19

what are the functions of granulosa cells

Answer 19

nourish the oocyte
secrete chemical messengers
secrete antral fluid
site of action for oestrogen and FSH in the control of follicular development
expresses aromatase
secretes inhibin
site of action for LH during formation of the corpus luteum

Question 20

what happens if there is no zygote implantation

Answer 20

no hCG
CL dies
progesterone and oestrogen decrease

Question 21

what is the function of hCG

Answer 21

maintains CL which continues to secrete progesterone

Question 22

what are the other effects of oestrogen

Answer 22

increases the motility of the fallopian tubes
causes proliferation of the endometrium
secondary sexual characteristics

Question 23

what are the effects of progesterone

Answer 23

causes secretory activity in the endometrium

catabolic
cervical mucous increase

Question 24

how does the combined pill work

Answer 24

inhibits FSH secretion by mimicking luteal phase 
no follicular growth 
no ovulation and no corpus luteum 
low oestrogen synthesis 
no build up of endometrium

Question 25

what hormones causes the granulosa cells to proliferate and secrete oestrogen

Answer 25

FSH

Question 26

what is the function of the theca externa

Answer 26

During ovulation, the surge in LH increases cAMP which increases progesterone and PGF2α production. The PGF2α induces the contraction of the smooth muscle cells of the theca externa, increasing intrafollicular pressure. This aids in rupture of the mature oocyte

Question 27

what is the function of the theca interna

Answer 27

contains LH receptors

produces androgens which are then converted to oestrogens by the granulosa cells

Question 28

what are granulosa cells homologous to

Answer 28

sertoli

they both convert androgens to oestrogens