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BS - Reproductive System > Menstrual Cycle > Flashcards

Menstrual Cycle Flashcards

1
Q

When does the menstrual cycle begin and end?

A

It begins at menarche and ends at menopause

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2
Q

What are the 4 purposes of the menstrual cycle?

A
  1. generate oocyte
  2. facilitate fertilisation
  3. optimise endometrium for implantation
  4. protect the developing embryo
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3
Q

How is the menstrual cycle divided into 2 phases?

A

Follicular phase runs from day 1 - 14

Luteal phase runs from day 14 to 28

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4
Q

How is the menstrual cycle divided into 3 phases?

A

Menstrual phase runs from day 1 - 5

Proliferative phase runs from day 5 - 14

Secretory phase runs from day 14 - 28

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5
Q

What happens during the menstrual phase?

A

Menstruation

This is when the uterine lining is shed

Levels of oestrogen and progesterone are low

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6
Q

What happens during the proliferative phase?

A

The endometrium thickens

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7
Q

What happens during the secretory phase?

A

The uterine lining produces chemicals that will:

  1. support an early pregnancy
  2. prepare the lining to break down if pregnancy does not occur
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8
Q

What happens during the follicular phase?

A

This is the time between the start of the menstrual cycle and ovulation

Oestrogen levels are high

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9
Q

What happens during the luteal phase?

A

This is the time between ovulation and the start of menstruation

Progesterone levels peak and then drop

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10
Q

What is the name of the axis involved in endocrine control of the menstrual cycle?

A

Hypothalamo-pituitary-ovarian axis

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11
Q

What is involved in endocrine control through the hypothalamo-pituitary-ovarian axis?

A
  1. hypothalamus secretes GnRH
  2. GnRH stimulates the anterior pituitary gland to release FSH and LH
  3. FSH and LH travel to the ovary
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12
Q

What is the example of negative feedback in the hypothalamo-pituitary-ovarian axis?

A

The ovary produces oestrogens

The oestrogens feedback on the hypothalamus and anterior pituitary

This prevents release of GnRH and FSH/LH

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13
Q

What is the structure of GnRH?

A

It is a decapeptide

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14
Q

What is GnRH secreted by and how often?

A

It is secreted by mid basal hypothalamic neurones

It is secreted in hourly pulses

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15
Q

How is GnRH transported to the anterior pituitary gland?

A

It is transported via the hypophyseal portal blood system

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16
Q

What 6 factors will affect secretion of GnRH?

A
  1. bereavement
  2. anxiety
  3. time zone
  4. day/night duty
  5. exercise
  6. weight loss/gain
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17
Q

Where are FSH and LH secreted from?

A

Basophils in the anterior pituitary gland

FSH and LH are glycoproteins

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18
Q

What is the role of FSH?

What hormone does it lead to the production of?

A

It stimulates follicular activity

It promotes estradiol production from granulosa cells

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19
Q

What is the role of LH?

What hormone does it lead to the production of?

A

It triggers release of egg from dominant follicle

It promotes development of the corpus luteum and production of progesterone

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20
Q

How is GnRH, LH and FSH production inhibited?

A

It is inhibited by rising E2 levels

This is negative feedback

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21
Q

What happens near midcycle relating to the levels of GnRH, LH and FSH?

A

Levels of E2 lead to a surge in LH release

This triggers ovulation

This is positive feedback

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22
Q

What are the follicles that are present in the ovary at birth?

How many are there?

A

Primordial follicles

There are 2,000,000 in the foetus at 6 months

23
Q

What happens to the numbers of follicles as age increases?

A

At birth - 750,000

At puberty - 400,000

Around 450 follicles develop and produce an egg - the rest degenerate

24
Q

How are new follicles produced?

A

No new follicles are produced

25
Q

What are the stages of follicular development leading up to ovulation?

A
  1. primordial follicle
  2. preantral follicle (primary)
  3. antral follicle (secondary)
  4. preovulatory follicle

OVULATION

26
Q

What is the first stage in follicular development?

A

Between the primordial follicle and the preantral follicle, there is proliferation of granulosa cells

27
Q

What is significant about the development of the antral follicle?

A

The antrum develops in the granulosa cells

This is a fluid-filled space which develops around the oocyte

28
Q

What are the layers of the follicle?

A
  1. oocyte is in the centre
  2. zona pellucida
  3. granulosa cells
    (antrum within this layer)
  4. theca
29
Q

What is the purpose of gap junctions and cytoplasmic processes between the oocyte and granulosa cells?

A

They allow for communication and passage of low molecular weight materials (nutrients)

30
Q

What develops after proliferation of thecal cells?

A

Theca interna and theca externa

31
Q

What is the difference between the theca interna and the theca externa?

A

The theca interna is glandular and highly vascularised

The theca externa is a fibrous capsule

32
Q

Why is interaction between follicular cell types critical?

A

Androgens are secreted by theca interna cells

These are converted to estradiol 17-B in granulosa cells

33
Q

What are the stages leading up to ovulation?

A
  1. high levels of E2 (estradiol) from almost mature follicle stimulate release of more GnRH and LH
  2. GnRH promotes release of FSH and more LH
  3. LH surge brings about ovulation
34
Q

What is meant by corpus hemorrhagicum?

A

This is a ruptured follicle

The follicle ruptures during ovulation when a secondary oocyte is released

35
Q

What is the name of the almost mature follicle?

A

Graafian follicle

36
Q

What happens to the empty Graafian follicle post-ovulation?

A

The granulosa cells undergo luteinisation

This leads to production of the corpus luteum after 12 days

37
Q

What happens to the corpus luteum if pregnancy occurs?

A

It secretes progesterone and oestradiol 17B

38
Q

What happens to the corpus luteum if there is no fertilisation?

A

The corpus luteum degenerates/fibroses

It becomes the corpus albicans

39
Q

What is the endometrium?

A

The lining of the uterus

40
Q

What happens to the endometrium during the proliferative phase?

A

The endometrium thickens

This is driven by estradiol - E2

There is an increase in stromal cells, glands and blood vessels

41
Q

How thick is the endometrium by ovulation?

A

By ovulation, the endometrium is 2-3 mm thick

42
Q

What is the dominant hormone during the secretory phase?

A

Progesterone

43
Q

What happens to the endometrium during the secretory phase?

A
  1. increased secretion
  2. increase in lipids and glycogen
  3. increased blood supply
44
Q

How thick is the endometrium by the end of the secretory phase?

A

4-6 mm thick

45
Q

How does the endometrium supply the optimal conditions for implantation of the fertilised egg?

A

It is stable, vascular and nutrient-rich

46
Q

What is the first stage in menstruation?

A

Vasodilation due to vasospasm of blood vessels

This is brought about by PGF2a

47
Q

What is the result of vasospasm of blood vessels?

A

The necrotic outer layers of the endometrium separate from the uterus

48
Q

What happens once the outer layers of the endometrium have separated from the uterus?

A

The separated tissue and blood initiate uterine contractions

This works to expel the contents

49
Q

What is produced from columnar glands in the cervix?

A

Mucus

50
Q

What is the mucus from the columnar glands like mid-cycle?

Why?

A

It is stringy and runny - spinnbarkeit

This facilitates sperm access at ovulation

51
Q

What is the mucus from the columnar glands like in the luteal phase?

Why?

A

It is tenacious and inelastic

This protects the developing embryo by preventing microbial ingress

It forms a mucus ‘plug’

52
Q

What is contained in the combined oral contraceptive?

A

Estradiol and progestagen

Progestagen is synthetic progesterone

53
Q

How does the combined oral contraceptive work?

A

It inhibits GnRH, FSH, LH through negative feedback

This prevents ovulation

It leads to a thin endometrium and tenacious mucus

54
Q

How is an egg collected for in vitro fertilisation?

A

Superovulation involves daily injections of FSH

BS - Reproductive System (12 decks)

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