hormonal control of the menstrual cycle Flashcards Preview

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Flashcards in hormonal control of the menstrual cycle Deck (28)
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1
Q

describe the pattern of FSH

A

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

2
Q

describe the pattern of LH

A

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.

3
Q

describe the pattern of oestrogen

A

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.

4
Q

describe the pattern of progesterone

A

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.

5
Q

describe the pattern of inhibin

A

similar to oestrogen

6
Q

what does low concentration oestrogen inhibit

A

FSH and LH

7
Q

what does inhibin do

A

inhibits secretion of FSH

8
Q

what does a dramatic increase in oestrogen do

A

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

9
Q

what does high progesterone in the presence of oestrogen do

A

inhibits FSH and LH during the luteal phase and pregnancy

10
Q

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

A

granulosa cells

homologous to sertoli cells

11
Q

what is the function of FSH

A

max conc during follicular phase

stimulates growth of medium sized follicles

12
Q

what is the function of LH

A

stimulates steroid hormone synthesis by the corpus luteum

stimulates ovulation

13
Q

what stimulates an increase in LH

A

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

14
Q

what cells are homologous to theca cells

A

Leydig

because they both synthesise androgens

15
Q

what do theca cells do

A

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

16
Q

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

A

FSH

17
Q

What causes the LH surge

A

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

18
Q

what are the effects of LH on the ovary

A

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

19
Q

what are the functions of granulosa cells

A

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

20
Q

what happens if there is no zygote implantation

A

no hCG
CL dies
progesterone and oestrogen decrease

21
Q

what is the function of hCG

A

maintains CL which continues to secrete progesterone

22
Q

what are the other effects of oestrogen

A

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

23
Q

what are the effects of progesterone

A

causes secretory activity in the endometrium

catabolic
cervical mucous increase

24
Q

how does the combined pill work

A
inhibits FSH secretion by mimicking luteal phase 
no follicular growth 
no ovulation and no corpus luteum 
low oestrogen synthesis 
no build up of endometrium
25
Q

what hormones causes the granulosa cells to proliferate and secrete oestrogen

A

FSH

26
Q

what is the function of the theca externa

A

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

27
Q

what is the function of the theca interna

A

contains LH receptors

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

28
Q

what are granulosa cells homologous to

A

sertoli

they both convert androgens to oestrogens