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Week 1 SEM 4 > 6. Menstrual Cycle > Flashcards

6. Menstrual Cycle Flashcards

1
Q

What are the aims of the menstrual cycle?

A 
selects single oocyte
regular spontaneous ovulation
support (potential) fertilized embryo
prepare the uterus
endometrium lining growth
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2
Q

What is GnRH and LH/FSH release co-ordinated with?

A

Follicle growth

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3
Q

Hoq long is the menstrual cycle?

A

28 days

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4
Q

How long does the follicular phase last?

A

14 days (but can vary)

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5
Q

What happens in the follicular phase?

A
  1. Select dominant follicle

2. Follicle growth

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6
Q

What is the follicular phase dominated by?

A

Oestradiol (produced from dominant follicle)

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7
Q

How long is the luteal phase?

A 
14 days (fixed)
happens after ovulation
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8
Q

What is the luteal phase dominated by?

A

Progesterone (released by corpus luteum)

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9
Q

What is day 1 of the menstrual cycle?

A

bleed (first day of period)

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10
Q

What is the midpoint of the menstrual cyycle?

A

Ovulation of the selected dominant follicle= day 14

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11
Q

What is the corpus luteum

A

After egg has been released, whatever is left is the corpus luteum
releases progesterone

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12
Q

Whathappens to the corpus luteum if there is no fertilization or pregnancy?

A

corpus luteum dies
instigates new cycle to start
when corpus luteum dies,endometirum (lining of the womb) sheds and then get menstrual bleed

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13
Q

Other than androgens, oestrogens and progestogens, what are the other 2 proteins that act on the HPG acis?

A

activin and inhibin

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14
Q

What do activin and inhibin act on in the HPG axis?

A

pituitary

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15
Q

What kind of feedback is it in the luteal phase?

A

negative feedback (through progesterone)

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16
Q

What kind of feedback is it in the follicular phase?

A

Variable feedback

  1. negative feedback from luteal is released (so no negative feedback)
  2. negative feedback back to normal
  3. negative feedback to positive feedback switch
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17
Q

What happens in late luteal/early follicular phase?

A
  1. corpus luteum dies
  2. so less progesterone
  3. progesterone always makes negative feedback- so now no more negative feedback
  4. so FSH rises=INTERCYCLE RISE OF FSH
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18
Q

What is FSH needed for?

A

for antral follicle growth

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19
Q

What happens in the midfollicular phase?

A
  1. high FSH
  2. antral follicles can grow bc granulosa cells release oestrogen
  3. oestrogen act on pituitary and hypothalamus= negative feedback
  4. FSH drops
  5. lots of follicles die except dominant
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20
Q

What switches the feedback from negative to positive?

A

dominant follicle releases oestrogen (above 300pmol) for 48 hours

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21
Q

What happens in the midcycle stage?

A

oestrogen levels high
so LH surge
LH causes ovulation

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22
Q

What happens in the midluteal stae?

A

1, corpus luteum secrete progesterone

2. negative feedback again

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23
Q

What other sources of feedback affects the hypothalamic-ovarian axis?

A
  1. FAT SIGNALS (lepting, oestrol)
  2. INSULIN
  3. CORTISOL
24
Q

In what condition, do women have high insulin levels (hyperinsulinaemia)?

A

polycystic ovary syndrome- the women can get insulin resistance- this affects follicle growth

25
Q

How do fat signals feedback into the HPO axis?

A

They influence GnRH and gonadootrophins

26
Q

What does the fall in FSH allow?

A

dominant follicle to be chosen

27
Q

What is the window of opportunity?

A

when the FSH rises, the antral follicles can grow. when they reach right stage they are recturited into menstrual cycle and continue to grow

28
Q

Where does follicle selection occur?

A

in either ovary

29
Q

How does the dominant follicle survive?

A

has FSH receptors

gets LH receptors on granulosa cells

30
Q

What receptors do theca cells have?

A

ONLY LH RECEPTORS= androgen and progesterone production

31
Q

What receptors do granulosa cells have?

A

FSH

dominant follicle granulosa cells acquire LH receptors (mid follicular phase onwards)

32
Q

Which cells take up cholestrol?

A

theca and granulosa

33
Q

How many primordial follicles exist when a baby is born and how many get recruited to menstrual cycle?

A

4000 (in baby) to 400 (in cycle)

34
Q

How long does the dominant follicle take to grow?

A

in 7 days from 7mm to 14mm diameter

35
Q

Where does a follicle grow?

A

In the medulla of the ovary

36
Q

When a dominant follicle is selected, where does it go?

A

to the cortex (of ovary)

37
Q

What are the cascade of events during ovulation?

A 
increase blood supply to follicle
stigma on ovarian wall
protease release (digest the wall)
38
Q

What is extruded from the ovary wall?

A

oocyte with cumulus cells under high pressure= so fluid can pour into pouch of douglas (rectouterine)

39
Q

How does the egg move down the tube?

A

peristalsis and cilia

40
Q

How long does an oocyte stay a primary oocyte?

A

from foetal ovary to ovulation- arrested in first meiotic division

41
Q

When does the nucleus of the oocyte complete first meiotic division?

A

after the LH Surge

42
Q

What is the first polar body?

A

half of the chromosomes of the egg are put in this first polar body

43
Q

What receptors does the corpus luteum have?

A

LH

44
Q

What is the corpus luteum supported by?

A

LH and hCG (until placenta is established)

45
Q

What does the corpus luteum secrete and what do they do?

A 
PROGESTERONE:
prepare endometrium 
controls fallopian tube cells
OESTROGEN:
endometrium health
46
Q

How are periods written in clinical notes?

A

7/28 (7days menses/ 28 day cycle)

47
Q

Why does the luteal phase only last 14 days?

A

because it depends on the demise of the corpus luteum

48
Q

When is it best to have intercourse?

A

If cycle is regular, then bang in the middle

49
Q

Where are androgens made?

A

only in theca cells

can be aromatised in granulosa cells to oestrogens

50
Q

What things feed into the HPG axis?

A
  • Nutritional systems
  • Adipocytes via leptin
  • Pancreas feeds into the cycle via insulin
  • Liver feeds in via IGF-1
  • Adrenals feed in e.g. corisol
  • VEGF, TGF-beta also feed in
51
Q

When is the dominant follicle selected?

A

midfollicular phase

52
Q

How does a patient know when they are going to ovulate?

A

ultrasound monitoring- can see dominant follicle

ovulation sticks-detect LH (18 hours after LH surge there is ovulation) =EXPENSIVE

53
Q

Why is oocyte stuck at first meiotic division at anaphase?

A

retain all its DNA and remain as large as possible.

54
Q

What is the FSH threshold hypothesis?

A

One follicle from the group of antral follicles in ovary is just at the right stage at the right time….
This becomes the dominant follicle which goes onto ovulate
Known as “selection”
Can be in either ovary

55
Q

What are the clinical applications of negative feedback?

A

Look at analogude- if thinking of treating early puberty or to delay early puberty or want to induce delayed puberty
Pulsatile treatment- gonadotrophin injections- pulsatile
HRT- in menopause
Part of fertility treatment- clomid-occupies oestrogen receptors- stops oestrogen binding to its receptors- stops negative feedback- allows follicles to grow up with endogenous FSH produced by women

Week 1 SEM 4 (7 decks)

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