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MD3002 Physiology > Menstraul Cycle ans its jormonal control > Flashcards

Menstraul Cycle ans its jormonal control Flashcards

1
Q

How long is the menstraul cycle?

A

Mean 28 days (+/- 3.95) for about 40 years

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2
Q

When does menopause occur?

A

45 - 55 (average 51 years) and marks the end of natural fertility

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3
Q

What is Premature ovarian failure?

A

Menopause can occur in women under the age of 40 (idiopathic, autoimmune disorders, genetic disorders such as fragile X, chemotherapy, radiation)
- Symptoms can be treated with oestrogen replacement (hormone replacement therapy - HRT)

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4
Q

When does ovulation occur in the menstraul cycle?

A

14 days

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5
Q

What is the phase called before ovulation?

A

Follicular phase

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6
Q

What is the phase called after ovulation?

A

Luteal phase

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7
Q

At what point in the menstraul cycle does 1 follicle become dominant?

A

Day 7 - the dominant follicle then matures from day 7 to 14/ovulation

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8
Q

When in the menstraul cycle does the corpus luteum degenerate?

A

Day 25 - 28

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9
Q

What are the uterine phases and when do they occur?

A
  • Menstraul: day 1 - 5
  • Proliferative: day 5 - 13
  • Secretory: day 13 - 28
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10
Q

What are the anterior pituitary gonadotropins?

A
  • LH

- FSH

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11
Q

What are the gonadal sex hormones?

A
  • Oestrogen

- Progesterone

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12
Q

What is in higher concentration in the plasma LH or FSH?

A

LH

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13
Q

Describe how FSH concentrations vary throughout the menstraul cycle?

A

Increases in early part of follicular phase, then steadily decreases throughout remainder of cycle EXCEPT small midcycle peak

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14
Q

Describe how LH concentrations vary throughout the menstraul cycle?

A

Constant during most of follicular phase, then large midcycle increase (LH surge) peaking ~18h before ovulation. Then rapid decrease with further slow decline during the luteal phase

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15
Q

Describe how oestrogen concentrations vary throughout the menstraul cycle?

A

Low and stable for 1st week, increases rapidly in 2nd weeks, starts to decline before LH peak. Then second increase due to corpus luteum in last few days of cycle.

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16
Q

Describe how progesterone concentrations vary throughout the menstraul cycle?

A

Low level due to ovary release during follicular phase with small increase just before ovulation. Soon after ovulation, large increase due to CL release, then similar pattern to oestrogen

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17
Q

Describe how inhibin concentrations vary throughout the menstraul cycle?

A

Similar pattern to oestrogen ie increases in late follicular phase, remains high during luteal phase, decreases as corpus luteum degenerates

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18
Q

How does oestrogen affect the concentrations of FSH and LH?

A
  • In low plasma concentrations, causes the anterior pituitary to secrete less FSH and LH in response to GnRH and also may inhibit the hypothalamic neurons that secrete GnRH
  • When oestrogen increases dramatically it causes anterior pituitary cells to secrete more LH and FSH in response to GnRH. Oestrogen can also stimulate the hypothalamic neurons that secrete GnRH
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19
Q

How does inhibin affect FSH?

A

Inhibin acts on the pituitary to inhibit the secretion of FSH
(-ve feeback inhibition of FSH secretion throughout the cycle)

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20
Q

What inhibits the hypothalamic neurons that secrete GnRH?

A
  • High plasma concentrations of progestone, in the presence of oestrogen
  • Results in -ve feedback inhibition of FSH and LH secretion and prevention of LH surges during the luteal phase and pregnancy
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21
Q

What does FSH stimuate?

A
  • In the first week of the follicular phase it stimulates the growth of medium sized follicles
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22
Q

What cells express FSH receptors?

A
  • Granulosa cells of the ovary during the follicular phase of the menstraul cycle
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23
Q

What are granulosa cells homologous to in men?

A

Sertoli cells of the testis

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24
Q

When does LH rise dramatically and what is it stimulated by?

A

12 hours before ovulation

- Stimulated by an increasing rate of secretion of oestrodiol-17B

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25
Q

What does LH stimulate by the corpus luteum?

A

Steroid hormone biosynthesis during the secretory phase

26
Q

What does LH do?

A

Stimulates Theca cells to synthesize androgens

27
Q

What is the main androgen produced?

A

Androstenedione

28
Q

What stimulates granulosa cells to convert androgens to estrogen?

A

FSH

29
Q

What is androstenedione converted to in granulosa cells?

A

Oestrodiol 17B

30
Q

What is the LH and FSH surge caused by?

A

MId-cycle shift of oestrogen from -ve to +ve feedback

- Caused by upregulation of receptors (eg GnRH in anterior pituitary) when oestrogen levels are increased

31
Q

What does the dominant follicle secrete?

A

Large amounts of oestrogen

- Acts on anterior pituitary (and possibly hypothalamus) to cause LH surge

32
Q

What does increased plasma LH stimulate?

A

Triggers ovulation and formation of corpus luteum

33
Q

What cells mediate the action of LH?

A

Granulosa cells

34
Q

What are the functions of the granulosa cells?

A
  • Nourish oocyte
  • Secrete chemical messangers that influence the oocyte and theca cells
  • Secrete antral fluid
  • Are the site of action for oestrogen and FSH in the control of the follcle development during early and middle follicular phases
  • Express aromatase, which converts androgen (from theca cells) to oestrogen
  • Secrete inhibin, which inhibits FSH secretion via an action on the pituitary
  • Are the site of action for LH induction of changes in the oocyte and follicle culminating in ovulation and formation of the corpus luteum
35
Q

WHat happens to LH and FSH levels in the luteal phase?

A

Suppressed

36
Q

What happen in the luteal phase if no implantation?

A
  • hCG does not appear in blood
  • CL dies
  • Progesterone and oestrogen decrease
  • Menstruation occurs and next MC begins
37
Q

What organ is the source of the timing of the menstraul cycle?

A

Ovaries

38
Q

What happens if progesterone remians high?

A
  • Levels of LH and FSH will be suppressed and ovulation will not occur
  • Occurs in pregnancy, human chorionic gonadotropin produced by placenta maintains corpus luteum which continues to secrete progesterone
39
Q

What hormone is exploited therapeutically in oral contraceptive pills?

A

Oestrogen

- Suppresses LH and FSH and prevents ovulation

40
Q

What happens in the menstraul phase?

A

Epithelail lining of uterus (endometrium) degenerates

41
Q

What happens during the proliferative phase?

A
  • Menstraul flow ceases
  • Under influence of oestrogen, endometrium thickens
  • Growth of unerlying smooth muscle (myometrium) also occurs
  • Synthesis of receptors for progesterone in endometrial cells also occus
  • Is part of ovarian folicular phase
  • Lasts for ~10 days until ovulation
42
Q

What happens during the secretory phase?

A
  • Begins soon after ovulation
  • Endometrium increases secretory activity under influence of progestone
  • Endometrial glands become coiled, filled with glycogen, blood vessels become more numerous, enzymes accumulate in glands and connective tissue, all to make endometrium a hospital environment for implantation and nourishment of developing embryo
  • Coincides with ovarian luteal phase
  • Spiral arteries develop alongside complex, hackshae shaped glands
  • Secretion in the glands is rich in glycoprotein sugars and amino acids
  • Enlargement of myometrial cells but depressed overall excitability
43
Q

When is the ischaemic phase (if included)?

A

At the end of the secretory phase

44
Q

What happens during the ischaemic phase / end of secretory phase?

A
  • Loss of steroid support
  • Constriction of spiral arteries
  • Ischaemia and collapse of endometrium
  • Seperation of basal and functional layers
  • Functional layer is shed as menstraul bleeding increase in neutrophils
45
Q

How many cycles are there for the average healthy woman?

A

450

46
Q

Why is there no clotting of menstraul blood?

A

Endogenous fibrinolytic activity

47
Q

What is the normal amount of blood produced during mensruation?

A

30 - 80 mls

48
Q

What is dysmenorrhoea?

A
  • Painful contractions

- 15% seek analgesia

49
Q

What are the effects of oestrogen?

A
  • Stimulates growth of ovary and follicles (local effects)
  • Stimulates growth of smooth muscle and proliferation of epithelial linings of reproductive tract
  • Stimulates external genitalia growth, particularly during puberty
  • Stimulates breast growth, particularly ducts and fat deposition during puberty
  • Stimulates female body configuration during puberty: narrow shoulders, broad hips, , female fat distribution (deposition on hips and breasts)
  • Fluid secretion from lipid - producing skin glands
  • Bone growth and cessation
  • Vascular effects
  • Feedback effects on hypothalamus and ant pituitary
  • Stimulates prolactin secretion but inhibits prolactin’s milk-inducing action on the breasts
  • Protects against atherosclerosis by effects on plasma cholesterol, blood vessels and blood clotting
50
Q

What are the effects of progesterone?

A
  • Converts the oestrogen-promed endometrium to an actively secreting tissue suitable for implantation of an embryo
  • Induces thick, sticky cervical mucus
  • Decreases contractions of fallopian tubes and endometrium
  • Decreases proliferation of vaginal epithelial cells
  • Stimulates breast growth, particularly glandular tissue
  • Inhibits feedback effects on hypothalamus and ant pituitary
  • Increases body temperature
51
Q

What is oligomenorrhoea?

A

Infrequent light periods

52
Q

What is metorrhagia?

A

Irregular bleeding

53
Q

What is dysmenorrhoea?

A
  • Painful periods
  • Main cause is overproduction of prostaglandins produced by endometrium in response to decrease in plasma oestrogen and progesterone
54
Q

What is polymenorrhoea?

A

Frequent periods

55
Q

What is amenorrhoea?

A

No periods

56
Q

What is premenstrual syndrome and premenstrual dysphoric disorder?

A
  • PMS - 75% of women who experience symptoms which affect their everyday quality of life
  • PMDD - 3-8% More serios can be temporarily disabling (eg anxiety, mood swings, tiredness, depression, headaches, abdo pain)
57
Q

What is thought to be the cause of some of the symptoms associated with PMDD and PMS?

A

Falling levels of progesterone at the end of the cycle - progesterone is thought to have an anxiolytic effect

58
Q

What are the primary causes of amenorrhoea?

A
  • Anatomical/congenital abnormality e.g underdevelopment or absence of uterus/vagina
  • Genetic e.g. Turner’s syndrome
59
Q

What are the secondary causes of amenorrhoea?

A
  • Pregnancy
  • Lactation
  • Exercise/nutrition
  • Menopause
  • Polycystic ovarian syndrome
  • Iatrogenic (surgery, medication)
60
Q

What is included in the female athlete triad?

A
  • Exercise
  • Nutrition
  • Amenorrhoea
61
Q

What is Lactational amenorrhea?

A

the temporary postnatal infertility that occurs when a woman is amenorrheic (not menstruating) and fully breastfeeding

MD3002 Physiology (24 decks)

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