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Phase 3a - Women's Health > Women's Health : The Menstrual Cycle > Flashcards

Women's Health : The Menstrual Cycle Flashcards

1
Q

The menstrual cycle begins with _____ follicles

A

15-20

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2
Q

Which type of follicle undergoes ovulation?

A

Graafian follicle

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3
Q

What are the 5 components of a follicle?

A
  1. A primary oocyte 2. A zona pellucida - a protein coat surrounding the oocyte 3. Granulosa cells - these express FSH receptors, which stimulates them to convert androgens produced by theca cells into oestradiol. 4. A fluid-filled antrum. 5. Theca cells - these express LH receptors, and produce androgens.
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4
Q

What is the zona pellucida?

A

Protein coat of oocyte- a protein coat surrounding the oocyte

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5
Q

What do granulosa cells express?

A

FSH receptors

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6
Q

What do FSH receptors stimulate?

A

stimulates them to convert androgens produced by theca cells into oestradiol.

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7
Q

What is the role of granulosa cells?

A

Convert androgens to oestradiol

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8
Q

What type of receptor do theca cells express?

A

LH receptors

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9
Q

What do theca cells produce?

A

Androgens

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10
Q

What happens to granulosa cells after ovulation?

A

After ovulation, the granulosa cells of the ruptured Graafian follicle undergo luteinisation to become the progesterone-secreting corpus luteum - this has a 10 day lifespan before it begins atresia (continues secreting progesterone for 14 days).

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11
Q

What are the names of the phases of the menstrual cycle?

A

The menstrual cycle is therefore split into the follicular and luteal phases, separated by ovulation.

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12
Q

What does the corpus luteum secrete?

A

Progesterone

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13
Q

What is the lifespan of the corpus luteum?

A

10 days

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14
Q

How long does the corpus luteum continue to secrete progesterone?

A

14 days

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15
Q

What dictates the menstrual cycle?

A

hypothalamic-pituitary-gonadal (HPG) axis.

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16
Q

Where is Gonadotrophin-releasing hormone (GnRH) released from?

A

Hypothalamus

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17
Q

GnRH travels from ______ to _____ via ______________

A

GnRH Travels from hypothalamus to anterior pituitary via hypophyseal portal vessel system

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18
Q

What is the secretion pattern of GnRH?

A

Secreted in a pulsatile manner at varying frequencies i.e. higher frequency, lower amplitude in follicular phase, and lower frequency, higher amplitude in luteal phase.

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19
Q

GnRH stimulates the secretion of ___ and ____

A

LH and FSH

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20
Q

GnRH is inhibited by ___ and ___ (negative feedback)

A

LH and FSH

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21
Q

Luteinising hormone (LH) and follicle-stimulating hormone (FSH) are released from?

A

Anterior Pituitary

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22
Q

LH and FSH are _____ hormones, collectively known as the _______ (and are produced by cells called _______)

A

Peptide hormones, collectively known as the gonadotrophins (and are produced by cells called gonadotrophs).

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23
Q

LH acts on which cells?

A

Theca cells

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24
Q

What does LH cause?

A

LH causes theca cells to produce androgens

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25
Q

FSH acts on which cells?

A

Granulosa cells

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26
Q

What is the effect of FSH on granulosa cells?

A

Convert androgens to oestrogen

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27
Q

Where do oestrogen and progesterone come from?

A

Follicles in the ovary

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28
Q

What type of hormones are oestrogen and progesterone?

A

Steroid hormones

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29
Q

At moderate levels, oestrogen exerts _______ feedback upon LH secretion

A

negative

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30
Q

At high levels, oestrogen exerts ____ feedback upon LH secretion

A

positive

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31
Q

When does oestrogen peak?

A

Mid-cycle

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32
Q

When does progesterone peak?

A

Day 21

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33
Q

Describe the levels of progesterone

A

progesterone is low throughout the follicular phase, but peaks 7 days before a menstrual bleed (i.e. day 21 of a 28 day cycle).

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34
Q

What feedback does progesterone exert?

A

Progesterone exerts negative feedback on GnRH secretion, reducing the frequency of its pulsatile secretion during the luteal phase.

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35
Q

What prepares the uterus for a fertilised oocyte?

A

Endometrium changes

36
Q

What are the three layers of the endometrium?

A

The endometrium has three layers, which are also separated into two strata by their functionality in the menstrual cycle:Stratum functionalis, composed of the stratum spongiosum and stratum compactum

37
Q

What are the two strata of the stratum functionalis?

A

Stratum spongiosum, Stratum compactum

38
Q

The stratum functionalis proliferates under the influence of oestrogen in advance of ovulation - what are the 4 stages of this?

A
  1. Stratum spongiosum thickens through mitosis 2. Endometrial glands lengthen 3. Connective tissue stroma regenerates 4. Spiral arterioles lengthen
39
Q

After ovulation, _______ acts upon the endometrium to cause it to secrete substances including ______ and _______ - this makes it more accommodating to a potentially fertilised oocyte

A

After ovulation, progesterone acts upon the endometrium to cause it to secrete substances including glycogen and mucous - this makes it more accommodating to a potentially fertilised oocyte

40
Q

What happens if conception does not take place?

A

There is no beta-hCG to maintain the corpus luteum, leading it to spontaneously regress

41
Q

With the withdrawal of its progesterone, the stratum functionalis degenerates and causes a menstrual bleed: Describe the 3 stages of this.

A
  1. Spiral arteriolar constriction causes tissue ischaemia. 2. Leukocyte infiltration into stratum functionalis takes place. 3. Spiral arterioles rupture
42
Q

What does spiral arteriolar constriction cause?

A

Tissue ischaemia

43
Q

What infiltrates the stratum functionalis?

A

Leukocytes

44
Q

What ruptures leading to menstrual bleed?

A

Spiral arterioles

45
Q

__________ release plays a significant role in inducing the menstrual bleed

A

Local Prostaglandin

46
Q

What phase occurs during Days 1-14?

A

Follicular Phase, Menses and Proliferative Phase

47
Q

Increased frequency of pulsatile GnRH secretion leads to an increase in __, and an initial increase in ___

A

Increased frequency of pulsatile GnRH secretion leads to an increase in LH, and an initial increase in FSH

48
Q

How do oestrogen levels increase (days 1-14)?

A

Oestrogen rises gradually as granulosa cells convert thecal androgens under the influence of FSH.

49
Q

Why do progesterone levels remain low (days 1-14)?

A

Progesterone levels remain low after loss of corpus luteum

50
Q

What feedback do moderate oestrogen levels exert?

A

Negative on FSH

51
Q

What occurs during Days 1-5?

A

Menstrual bleed

52
Q

What causes the menstrual bleed?

A

Progesterone withdrawal due to degeneration of corpus luteum leads to sloughing of the stratum functionalis (a menstrual bleed).

53
Q

What phase does the endometrium undergo from days 6-14?

A

Proliferative phase due to rising oestrogen levels

54
Q

What happens during days 15-20

A

early antral (tertiary) follicles undergo development

55
Q

What occurs on day 7 of the ovarian cycle?

A

a single dominant follicle is selected.( it is thought that this occurs because rising oestrogen levels lower FSH levels through negative feedback - the dominant follicle is the one that can cope with lower FSH.)

56
Q

What happens on day 13 related to LH?

A

Rising oestrogen levels reach a ‘tipping point’, at which their negative feedback on LH secretion is reversed - the LH surge occurs, stimulating the oocyte to complete meiosis I and form a single Graafian follicle.

57
Q

What triggers ovulation on day 14?

A

Antral fluid

58
Q

What happens on Day 14?

A

Ovulation - The secondary oocyte erupts from its follicle, carried by antral fluid.

59
Q

Days 15-28

A

Luteal phase and Secretory phase

60
Q

What happens to granulosa cells on Day 15?

A

the granulosa cells of the ruptured follicle become luteinised, forming the progesterone-secreting corpus luteum.

61
Q

What does the corpus luteum secrete?

A

Progesterone.

62
Q

What phase does the endometrium enter due to progesterone?

A

The corpus luteum’s progesterone acts upon the endometrium to cause it to enter its secretory phase - amongst other things, it secretes glycogen and mucous.

63
Q

When do progesterone levels peak?

A

7 days before the next menstrual bleed - 7 days before CL completely degenerates.

64
Q

What do high levels of progesterone affect?

A

High levels of progesterone increase the volume and viscosity of cervical secretions; this begins the formation of the protective operculum.

65
Q

What happens after 10 days if no conceptus implants?

A

the corpus luteum spontaneously regresses –> diminishing progesterone levels

66
Q

What impact does low progesterone levels have on the endometrium?

A

Without progesterone’s negative feedback on the hypothalamus, GnRH release frequency increases and facilitates a rise in gonadotrophins. ○ Progesterone withdrawal also stimulates the stratum functionalis of the secretory endometrium to be shed

67
Q

What causes the cycle to restart on Day 1?

A

As FSH and LH levels rise, and the menstrual bleed begins, the cycle restarts on Day 1.

68
Q

How many oocytes does a developing female foetus synthesise in utero?

A

A developing female foetus synthesises upwards of 6 million oocytes while in utero.

69
Q

How many oocytes remain by puberty, and what process reduces their number?

A

Approximately 300,000 oocytes remain by puberty due to a process called atresia.

70
Q

What are the two broad categories of follicles?

A

Follicles are categorized as pre-antral and antral.

71
Q

Which follicular phases are included in the antral category?

A

The antral phase includes primordial, primary, and secondary follicles.

72
Q

What is a primordial follicle, and what does it consist of?

A

A single oocyte arrested in prophase I of meiosis. A layer of flattened (squamous) granulosa cells.
A basal lamina (extracellular matrix).

73
Q

What happens to primordial follicles until puberty?

A

Until puberty, each oocyte remains part of a primordial follicle.

74
Q

How do primordial follicles transition to primary follicles?

A

Through recruitment, where a portion of primordial follicles enters the menstrual cycle.

75
Q

What changes occur in granulosa cells during the recruitment of primordial follicles to primary follicles?

A

Granulosa cells undergo mitosis.They change from a squamous to a cuboidal shape.
They start to express FSH receptors.

76
Q

What does the oocyte synthesize during the recruitment to primary follicles?

A

The oocyte synthesizes mRNA to encode proteins that form the zona pellucida.

77
Q

What are the components of a primary follicle?

A

A single oocyte.A surrounding zona pellucida.
A layer of cuboidal granulosa cells.
A basal lamina.

78
Q

What transformations occur in the primary follicle to form a secondary follicle?

A

The granulosa cell layer thickens through mitosis. Theca cells form around the basal lamina.
A network of blood vessels develops in the outer follicle.

79
Q

What is the tertiary follicle, and what happens at this stage?

A

The tertiary follicle, or early antral follicle, forms as a fluid-filled cavity (the antrum) develops within the granulosa cells.

80
Q

What happens to one of the tertiary follicles during the follicular phase?

A

One follicle undergoes selection to become the dominant follicle at the midpoint of the follicular phase.

81
Q

What event initiates the development of the dominant follicle into the Graafian follicle?

A

The LH surge initiates the development of the dominant follicle into the Graafian follicle.

82
Q

What effect does the LH surge have on the oocyte?

A

It takes the oocyte out of its meiotic arrest. The oocyte completes meiosis I, forming the first polar body.
It proceeds to metaphase II, where it is arrested again.

83
Q

What is a tertiary follicle with a complete antrum and a secondary oocyte called?

A

A Graafian follicle (an antral follicle).

84
Q

What are the components of a Graafian follicle from deep to superficial?

A

A secondary oocyte (plus the first polar body).Zona pellucida.
Cumulus oophorus of granulosa cells, attached to further granulosa cells.
A fluid-filled antrum.
Basal lamina.
Theca cells (interna and externa).

85
Q

What happens during ovulation?

A

The mature oocyte, along with its surrounding zona pellucida and cumulus oophorus of granulosa cells, hatches from the antrum.

86
Q

What cells are attached to the surrounding cumulus oophorus?

A

Granulosa cells

87
Q

What extracellular structure does the oocyte have surrounding it?

A

Zona pellucida

Phase 3a - Women's Health (21 decks)

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