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Physiology 2:Repro > The menstrual cycle > Flashcards

The menstrual cycle Flashcards

1
Q

what are the 6 aims of the menstrual cycle?

A

1)Selection of single oocyte
2)Regular spontaneous ovulation
3)correct number of chromosomes in eggs
4)Cyclical changes in vagina, cervic and fallopian tube
5)prep of uterus
6)support of fertilised dividing egg

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2
Q

How is the menstrual cycle highly controlled?

A

The release of LHRH/GnRH is pulsatile, which leads to the release of LH and FSH from the anterior pituitary, which acts on the gonads and the antral follicle and these eventually feedback oestrogen and progesterone to the pituitary and hypothalamus.

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3
Q

what are the 3 stages of the menstrual cycle?

A

1) Follicular phase
2)ovulation
3)Luteal phase
If oocyte isn’t fertilised you get menstruation

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4
Q

Briefly describe what occurs during the follicular phase (3)

A

1)From day 1 to ovulation
2)Dominant growth of the selection of follicle
3)oestrogen is produced

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5
Q

Briefly describe what occurs during the ovulation phase

A

You have a big follicle that ovulates the egg and the remainder of this follicle becomes the corpus loteum, which then secretes progesterone.
During ovulation the egg is released from the ovary and moves down the fallopian tube towards age uterus.

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6
Q

Briefly describe what occurs during the luteal phase

A

the corpus luteum forms from the empty follicle from which the egg was released from during ovulation. This causes the release of progesterone via negative feedback

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7
Q

what is a follicle?

A

small sac of fluid in the ovaries that contains a developing egg

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8
Q

what is the corpus luteaum and what is its function?

A

It is a cyst that forms in the ovary every single month.
Function= Make uterus healthy place for the foetus to grow, release the hormone progestrone to prepare the uterus for pregnancy.
Once enough progesterone is made CL goes away

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9
Q

what becomes of the empty follicle?

A

It becomes the corpus luteam

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10
Q

What is the role of oestrogen in regulating the menstrual cycle?

A

Makes the lining of the uterus- the endometrium, making it thicker and more receptive to a fertilised egg

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11
Q

what is the role of progesterone?

A

Prepare the endometrium for a fertilised egg to implant and grow.

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12
Q

what type of feedback Is there in the Luteal phase?

A

Progesterone= negative feedback

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13
Q

what type of feedback is there in the follicular phase?

A

variable feedback

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14
Q

describe the variable changes in feedback during the follicular phase

A

1) Release of negative feedback
2)Negative feedback then reinstated
3) Switch from negative to positive feedback

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15
Q

what is the hormone In males and what is its feedback?

A

Testosterone and it os via negative feedback

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16
Q

what is the hormone in females and what is its feedback? in the luteal and follicular phase

A

1)Progesterone which provides negative feedback via the luteal phase.
2)follicular phase= variable feedback- switch from negative to positive- remove the negative feedback from progesterone and reinstate the negative feedback by oestrogen and then you switch to positive feedback.

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17
Q

what is the difference between positive and negative feedback?

A

Positive= causes the levels of the hormone to increase
Negative= keeps the lvls of hormone within a relatively small range to maintain homeostasis

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18
Q

Progesterone is always what type of feedback?

A

Negative

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19
Q

why is it that during the luteal phase there is negative feedback of progesterone?

A

This is because the corpus luteam starts dying and so the progesterone that it was making falls.

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20
Q

what hormone is released from the hypothalamus in pulsatile release? where does this travel and what other hormones does it then cause the release of? this is in both males and females

A

1)Gonadotrophin releasing hormone
2) Travels to the anterior pituitary where it causes the release of LH and FSH

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21
Q

What happens as a result of the release of LH and FSH from the anterior pituitary in the female?

A

LH and FSH then travel to the ovary where they take affect.
LH= stimulates steroid release from ovaries, ovulation, and the release of progesterone after ovulation by the corpus luteam.
FSH= stimulates follicles in the ovary to grow and preps the egg for ovulation
Also causes testosterone to be released.

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22
Q

what hormone is released is released as FSH stimulates the follicles in the ovary to grow?

A

oestrogen

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23
Q

why does the release of Gonadotrophin releasing hormone have to be pulsatile?

A

If GnRH was continuous then the release of LH would drop

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24
Q

Explain the Hypothalamic/Pituitary/Ovarian axis

A

1)Pulsatile release of GnRH from the hypothalamus
2) GnRH causes positive feedback at the anterior pituitary gland, which causes the secretion of FSH and LH
3)These travel to the ovary, causing the release of oestrogen, progesterone and testosterone

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25
Q

describe the hormonal changes during late luteal/ early follicular phase.

A

After the CL breaks down the progesterone levels drop. The high progesterone was causing negative feedback at lvl of hyp/pit axis, therefore keeping the FSH/LH lvls low. Negative feedback removed, causing FSH lvls to increase, stimulating the follicle to grow.

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26
Q

describe the hormonal changes during mid follicular phase

A

As the follicle grows it makes estradiol, E2 (oestrogen). E2 inhibits FSH release, so lvls fall again.

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27
Q

during the follicular phase what is continually being released and what does this cause?

A

LH lvls have been rising a little across the follicular phase and this causes a single follicle to grow and grow and become the dominant follicle.It supports the growth but it is FSH that causes the growth.

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28
Q

what hormone does the dominant follicle make in large amounts?

A

E2/ oestrogen

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29
Q

describe the hormonal changes in mid cycle of the follicular phase

A

after 2 days of E2 lvls will reach above 300pmol, causing the negative feedback to become positive, causing a huge release of LH, which causes the egg to be released.

30
Q

describe the hormonal changes mid luteal phase

A

Once the egg is released after the LH surge the remaining follicle becomes the CL, which makes progesterone, causing the negative feedback.

31
Q

At the end of the luteal phase the corpus leteam dies out, causing what to occur?(on FSH, follicle and theca cell) explain the cycle (1-7)

A

1)when no pregnancy the corpus luteam dies out, causing the progesterone lvls to drop, removing the negative feedback on the gonadtrophins, causing selective release of FSH.
2)Early antral follicle responds to the FSH, causing it to grow.
3) Theca cells then cause increase in oestrogen production and this causes negative feedback on the dominant follicle and FSH drops.
4)Follicle starts to die as they lose their FSH stimulus, except for the dominant follicle that has been selected to ovulate.
4)Dominant follicle grows= oestrogen released (high conc causes switch to positive feedback)
5)Triggers big release of LH, triggering the ovulation of the dominant follicle and you get leutinisation of the rest of the follicle= corpus luteam
6) corpus luteam causes the release of progesterone, which causes the switch to negative feedback
7) corpus luteam dies off in the luteal phase and cycle starts again.

32
Q

why is the inter-cycle rise and fall of FSH important?

A

because it allows selection of a single follicle, which will go on to become the dominant follicle that will ovulate.

33
Q

Explain the ‘window of opportunity”/FSH hypothesis for DF selection

A

1) one follicle from the group of antral follicles in the ovary is just in the right stage at the right time to survive the declining FSH
2) This becomes the dominant follicle which goes on to ovulation
3)known as ‘selection’
4)can be in either ovary

34
Q

what prevents any further follicles form growing once the dominant follicle has been selected?

A

E2 lvls rise reinstating negative feedback at the pituitary causing FSH lvls to fall , preventing further follicle growth.

35
Q

how does the dominant follicle survive the fall in FSH?

A

There are many FSH receptors on the df so it doesn’t require a high conc to survive/ can survive at lower conc.

1)As FSH falls, LH increases so the df acquires lh receptors on granulosa cells
2)DF also increases sensitivity to FSH by increasing FSH receptors and increase number of granulosa cells
3)other follicles do not they lose their stimulant and die

36
Q

what are the 3 ways the dominant follicle survives falls in FSH?

A

1) increases FSH sensitivity as it produces more FSH receptors
2)Increased number of granulosa cells- aromatase enzyme present in the egg.
3)Acquire LH receptors- since the LH receptor gene is switched on by FSH

37
Q

what type of receptors are on theca cells? and why?

A

LH receptors.
LH binds to the receptors on the theca cells, causing androgen and progesterone production.

38
Q

what cells are located on the granulosa cells from mid-follicular phase onwards? and why?

A

FSH receptors and LH receptors, which drives oestrogen production in follicular phase

39
Q

where do all steroids originate from?

A

cholesterol

40
Q

what is steroidgenesis?

A

Steroidgenesis is the formation of steroid hormones by the sequential removal of carbon atoms by a series of enzymes, which are distributed through the cellular compartments of the follicle.

41
Q

describe the process of steroidgenesis

A

1) Acetate converted into cholesterol (containing 27 carbons)= occurs in both theca and granulosa cells
2)a side chain cleavage enzyme removes 6 carbons, forming pregnenelone (21 carbons)= occurs in both theca and granulosa cells
3)pregnenalone converted into progesterone (c21)= this occurs in both theca and granulosa cells via 17 alpha hydroxylase and 17,20 lyase
4) In the theca cells only progesterone is converted into the androgens and released :testosterone and androstenedione (19c)
5) In granulosa cells=the androgens testosterone and androstenedione is converted and released as oestrogen(c18) via the enzyme aromatase

42
Q

what is the name of the process in which thousands of primordial follicles die?

A

Atresia

43
Q

what is the LH surge responsible in triggering?

A

ovulation

44
Q

explain the process which causes the LH surge, resulting in the ovulation cascade.

A

by the end of the follicular phase if the oestrogen lvls raised above 300pM the feedback switched from negative to positive, which causes a massive release of LH from pituitary. This high LH causes the ovulation cascade:
1)Egg released
2)lutreinisation occurs, forming the corpus luteam
3) Corpus luteam has both luteinised granulosa and theca cells
4) Oestrogen production falls but is still produces and progesterone gets stimulated and dominates

45
Q

what is the ovulation phase?

A

when the mature egg is released from the ovary and moves down the fallopian tube towards the uterus.

46
Q

Ovulation occurs via a cascade of events. what are they?

A

1) Blood flow to the follicle increases dramatically
2) appearance of apex or stigma on the ovary wall
3)local release of proteases and inflammatory mediators
4) Enzymatic breakdown of protein of ovary wall
5) Follicle wall digested 12-18hrs after peak of LH and ovulation occurs with release of cumulus-oocyte complex
6)Oocyte with cumulus cells is extruded from the ovary
7)Follicular fluid may pour into the much of Douglas
8)egg collected by fimbria of uterine tube
9) egg progresses down tube by peristalsis and action of cilia

47
Q

what are the 2 types of cells in the lining of the fallopian tube? and what are their functions?

A

1) ciliated cells= helps waft the oocyte along the uterine tubes
2) non-ciliated cells= release a secretion that lubricates the tube and provides nourishment and protection to the travelling ovum

48
Q

At ovulation the oocyte and its cumulus cells and their matrix-the-cumulus-oocyte complex is released from the ovary. what property does the coc have and what does this do?

A

The Cumulus oocyte complex is released and it’s very sticky it travels down the tubes and the stickiness and outer coating protect the egg.

49
Q

Before the LH surge that induces ovulation what stage is the egg in? and what does it have to complete to get the haploid egg and what happens after?

A

Meiosis 1 arrest- it has to complete meiosis 1 to get the haploid egg. It then goes into arrest once again.

50
Q

Explain the 1st meiotic division of the oocyte.

A

1)From its formation as a primary oocyte in the fatal ovary up until ovulation, the oocyte has been arrested in the first meiotic division
2)This permits the oocyte to retain all the of the DNA and remain as large as possible during its long wait
3)In response to the LH surge, the nucleus of the oocyte in the dominant follicle completes the first meiotic division, but it does not divide.

51
Q

After what does the first meiotic division (meiosis 1) get completed and what is the name of the oocyte you get as a result?

A

After the LH surge the first meiotic division is complete and you get the secondary oocyte as a result.

52
Q

what is a secondary oocyte?

A

The mature egg, which is a haploid cell produced by meiosis.

53
Q

Another cell is formed whilst the secondary oocyte is formed. What is its name and function?

A

1st Polar body= This is where half of the chromosomes are put into a “small” package. This helps to leave behind a haploid cell.

54
Q

When does the egg complete meiosis 2 (the second meiotic division)?

A

After fertilisation

55
Q

what are the features that arise after the second meiotic division (Meiosis 2)

A

1)Laying down of the RNA
2)Protein formation that help to take the embryo through the early stages of development
3)All the mitochondria comes from the mother

56
Q

Is the oocyte the largest cell in the body?

A

yes

57
Q

Once meiosis 2 is complete what occurs?

A

Fusion

58
Q

What other structure is formed after ovulation and where does it originate from. What is its primary function? and what is the function of the hormone it releases?

A

The Follicle from which the egg was released from transforms into the corpus luteam and its primary function is to release progesterone and some oestrogen (mostly remember progesterone). The progesterone helps prepare the uterine lining (endometrium) for pregnancy, making it more receptive to a fertilised egg.

59
Q

what happens to the corpus luteam when the egg oocyte doesn’t get fertilised?

A

It breaks down (luteolysis) this causes the progesterone levels to drop, which triggers the shedding of the endometrium= period

60
Q

What kind of receptors are found on the corpus luteam?

A

LH receptors

61
Q

what 2 hormones influence the CL?

A

LH and hCG

62
Q

when is hCG produced and what affect does this have?

A

If the egg gets fertilised then hCG is released from the embryo (from syncytiotrophoblast of
embryo) and binds to the LHR. This maintains the CL until the placenta forms.

63
Q

within how many days will the CL die if the oocyte isn’t fertilised?

A

14

64
Q

what causes the cycle to start again after the CL breaks down when fertilisation doesn’t occur (resulting in a period)

A

The decline in progesterone

65
Q

What are the 2 secretions made by the CL and what are their functions?

A

1)Progesterone
-supports oocyte on its journey
-Prepares the endometrium
-Controls cells in the Fallopian tubes
-Alters secretions of the cervix
2)Oestradiol
-For endometrium

66
Q

Describe in days what happens during the menstrual cycle.

A

1)Day1 = First day of bleeding
2)Menstruation lasts 3-8 days (7/28 or 5-6/27-32)

67
Q

regular cycles should be no more than how many days variations?

A

4

68
Q

which phase of the menstrual cycle is fixed and why? and which phase is variable in the cycle?

A

The luteal phase- since the corpus luteum only has a lifespan of 14 days.
The Follicular phase is variable.

69
Q

How can you work out if a women is going to ovulate?

A

1)If they have a regular cycle- ovulation often occurs 14 days before the start of the next menstrual period
2)Rise in temperature- a woman’s body temp rises o.5-1 degree higher after ovulation
3)Egg White Consistency: Cervical mucus becomes more abundant, clear, and slippery, resembling egg whites, around the time of ovulation. This is a fertile cervical mucus that facilitates sperm movement.
4)LH surge
5)Ovulation pain
6)Changes in Cervical Position: The cervix changes position and becomes softer and more open around ovulation. Tracking these changes may help identify fertile days

70
Q

what are 6 signs of ovulation?

A

1)Temp rise
2)Tender breasts
3)Abdominal bloating
4)Light spotting
5)Changes in cervical nucus
6) Slight pain or ache on one side of the abdomen

71
Q

What hormone is used in an ovulation prediction kit?

A

LH

72
Q

Describe the hormonal changes in the menstrual cycle (throughout the different phases)

A

1)After the death of the CL= Progesterone lvls drop= this gives negative feedback
2)The negative feedback allows for inter cycle release of FSH
3)All the small antral follicles that are at the right stage and size are recruited into the menstrual cycle
4)increase in FSH causes the astral follicles to grow and produce oestrogen
5)The increase in oestrogen means that you have the negative feedback of FSH and it becomes downregulated, causing the follicles to die all except for one = dominant follicle
6)Dominant follicle grows with the help of rich theca vasculature and you have the granulosa which produce oestrogen over a certain lvl
7)There is an increase in oestrogen and you get an LH surge
8)Any other follicle will die due to an increase in oestrogen and this keeps the dominant follicle growing.
9)There is a peak in LH which induces ovulation and there is leuteinisation and the remainder of the CL dies
10)A decrease in progesterone means you have an increase in FSH again to get the cycle.

Physiology 2:Repro (11 decks)

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