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Repro > Menstrual cycle > Flashcards

Menstrual cycle Flashcards

1
Q

When does the menstrual cycle begin and end?

A

Menarche to Menopause

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2
Q

Average menstrual cycle length

A

21-35 days (average 28)

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3
Q

What are the two cycles occuring in parallel in the menstrual cycle?

A

Ovarian cycle
Uterine cycle

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4
Q

Two phases of ovarian cycle and their lengths

A

Follicular phase (varies)
Luteal phase (always 14 days)

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5
Q

What can we assume if the luteal phase always lasts 14 days?

A

Your day of ovulation is always 14 days before your last period

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6
Q

What does the menstrual cycle do?

A

Prepares for potential fertilisation and implantation

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7
Q

What controls the menstrual cycle?

A

HPG axis

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8
Q

Describe follicular phase

A

Day 1-14 (ish)

Day 1-7:Menstruation (period)
Day 8-11: Lining of womb thickens preparing for egg
Day 12-17: Ovulation (usually around day 14)

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9
Q

Describe luteal phase

A

Day x (ovulation) -> (x+14) always 14 days long

Ovulation
Day 18-25 - if fertilisation does not occur corpus luteum degenerates to corpus albicans
Uterine lining detaches –> menstruation

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9
Q

What is the role of FSH in cycle?

A

Stimulates maturation of ovarian follicle

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10
Q

What is the role of LH in cycle? (3)

A

Steroid release from ovart
ovulation (surge in LH)
progesterone release from corpus luteum

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11
Q

What exhibits negative feedback on FSH and LH?

A

Oestrogen, Progesterone and Inhibin

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12
Q

What do high levels of oestrogen lead to?

A

Positive feedback causing LH surge = ovulation

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13
Q

Ovarian cycle phases

A

2 phases -
Follicular phase day 1-14 (varies in length, preovulation)

Luteal phase - day 15-28, (always 14 days long, post ovulation)

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14
Q

3 phases of uterine cycle

A

Menstrual
Proliferative
Secretory

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15
Q

Uterine cycle and ovarian cycle together

A

Preovulation:
Follicular phase (ovarian) + menstrual and proliferative phase (uterine)

Postovulation:
Luteal phase (ovarian) + secretory phase (uterine)

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16
Q

Clinical importance of persistent presence of GnRH

(usually released in pulsatile manner and not always present)

A

Desensitisation of GnRH receptors
This would mean FSH and LH and gonadal steroids would not be produced

Agonists and analogues of GnRH can be used in treatment of endometriosis (decapeptyl/triptorelin pamoate)

Can cause infertility

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17
Q

Follicle development stages

A

Primordial follicle
Early pre-antral follicle
Late pre-antral follicle
Antral follicle
Pre-ovulatory/Graafian Follicle - ready for releasing the oocyte

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18
Q

Phases of ovarian cycle

A

Follicular phase - early and late phase
(Ovulatory phase)
Luteal phase

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19
Q

What happens in early follicular phase (day 0-5)?

A

No ovarian hormone (progesterone and oestrogen)

Granulosa cells secrete activin

FSH levels increase

Dominant follicle granulosa cells produce inhibin (instead of activin)

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20
Q

What does granulosa cells secreting activin lead to in early follicular phase?

A

Increased FSH production

Increase FSH receptors on granulosa cells

Reduced production of androgens by theca cells - less oestrogen

21
Q

What happens when FSH levels increase in early follicular phase?

A

Stimulates follicle growth

Theca interna appears

Enhanced aromatase function –> follicle is now capable of enhanced oestrogen production

22
Q

Why do the dominant follicle granulosa cells produce inhibin?

A

Selectively inhibits FSH - stop other follicles being matured

23
Q

What happens in the late follicular phase (day 5-14)?

A

Dominant follicle (Graafian) granulosa cells produce oestrogen and inhibin - these continue to rise

24
Q

What happens as a result of the Graafian follicle producing oestrogen?

A

Increased FSH receptors on follicle

Initally negative feedback to reduce FSH

Increased LH receptors on granulosa cells - ovulation prep

25
Q

What does Inhibin released from Graafian follicle cause?

A

Decreased FSH production (prevent other follicles developing)

Helps LH to increase theca cell androgen production (then converted to oestrogen)

26
Q

What happens in ovulatory phase of ovarian cycle (day 14)?

A

Oestrogen levels rise independent of FSH

(FSH not rising due to inhibin)

27
Q

What happens at day 14 due to high levels of oestrogen?

A

High levels exert +ve feedback on hypothalamus and anterior pituitary causing a SURGE in LH

= OVULATION

28
Q

What do the granulosa cells do at day 14 as ovulation occurs?

A

Start secreting progesterone from LH action

(can use this to see if someone has ovulated)

29
Q

Cell cycles at ovulation

A

Meiosis I is completed
Meiosis II begins but not completed yet

30
Q

Where does the mature oocyte go after ovulation?

A

Gets ejected from mature Graafian follicle at ovary, travels through capsule of ovary into fallopian tube (caught by fimbriae)

31
Q

What occurs in the luteal phase?

A

LH stimulates remaining follicle to develop into corpus luteum

32
Q

What does the corpus luteum do?

A

Secretes oestrogen and progesterone in large amounts - exerts -ve feedback on LH

Inhibin secreted - FSH remains low

Prepares endometrium for implantation

33
Q

Lifespan of corpus luteum

A

14 days +/- 2

34
Q

What happens in the waiting phase?

A

If fertilisation occurs - hCG is produced and maintains corpus luteum (in the ovary, was previously Graafian follicle)

If not, hormones plummet and corpus luteum degenerates into corpus albicans

35
Q

What controls what happens to the lining of the uterus?

A

Hormones made by the ovary - corpus luteum (oestrogen and progesterone)

36
Q

What effect does oestrogen have on the uterus epithelia?

A

Proliferative epithelium

37
Q

What effect does oestrogen + progesterone have on the uterus epithelia?

A

Secretory epithelium

38
Q

Layers of uterus

A

Perimetrium (outer layer)
Myometrium
Endometrium (inner)

39
Q

Layers of endometrium

A

Epithelium and stroma

Functional layer
Basal layer

40
Q

What do the functional and basal layers of endometrium do?

A

Functional - responsive to hormones, sheds in menstruation

Basal - develops into next new functional layer

41
Q

Endometrial changes in early proliferative

A

Sparse glands, straight (see page 18 on lecture for pics)

42
Q

Endometrial changes in late proliferative phase

A

Thicker functional layer, coiled glands

43
Q

Endometrial changes seen in secretory phase

A

Endometrial thickness at max
Very coiled glands
Coiled arteries (spiralled)

44
Q

What occurs at the end of the menstrual cycle if not fertilisation occurs?

A

Corpus luteum –> corpus albicans

Dramatic fall in oestrogen, progesterone and inhibin = loss of negative feedback and FSH rises

45
Q

What triggers menstruation?

A

Decrease in progesterone
–> new cycle begins

46
Q

What happens if fertilisation occurs?

A

Syncytiotrophoblast (will become placenta) produces hCG (human chorionic gonadotrophin)

This extends lifespan of corpus luteum before the placenta forms and takes over

47
Q

How can we test for ovulation?

A

Measure progesterone level at day 21 (7 days before period when they are levels are likely to be at their highest)

Measure temp - body temp increases if progesterone released

48
Q

Role of oestrogen

A

Follicular phase - nice hormone
- thickens endometrium
- growth and motility of myometrium
- thin alkaline cervical mucus (allow sperm in)
- changes in skin, hair and metabolism

49
Q

Role of progesterone

A

Luteal phase - not nice hormone
- further thickening of endometrium
- thickening of myometrium and reduction of motility
- thick, acidic cervical mucus (NO SPERM ALLOWED)
- development of breast tissue
- increased body temp
- metabolic and electrolyte changes

50
Q

What can cause disruptions to menstrual cycle?

A

Physiology - pregnancy, lactation
Emotional stress
Body weight

51
Q

What does high amounts of LH cause (LH surged caused by high oestrogen)?

A

Graafian follicle membrane becomes thinner
Follicle ruptures releasing secondary oocyte

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