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RGU Exam 1 > Menstrual Physiology > Flashcards

Menstrual Physiology Flashcards

1
Q

Menstrual cycle length and duration

A
  • Cycle length: 24-35 days
  • Duration: <8 days (Anything else is abnormal)
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2
Q

Luteal phase

A
  • 2nd phase of menstrual cycle that is always fixed at 14 days after ovulation (which occurs in the middle of the cycle)
  • After ovulation, granulosa and theca interna cells lining the wall of the follicle form the corpus luteum cyst (stimulated by LH)
  • The corpuse luteum synthesizes estrogen and large amoutns of progesterone
  • Progesterone stimulates the endometrium to become more glandular/secretory in preparation for implantation of fertilized ovum
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3
Q

Follicular phase

A
  • 1st phase of the menstrual cycle with variable timing
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4
Q

Ovarian perspective of the menstrual cycle

A
  • 1st half: Follicular
  • 2nd half: Luteal
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5
Q

Uterine perspective of the menstrual cycle

A
  • 1st half: Proliferative
  • 2nd half: Secretory
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6
Q

GnRH

A
  • Peptide hormone secreted by hypothalamus
  • Short half-life
  • Follicular phase: q 60-90min
  • Luteal phase: q 3-5hrs
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7
Q

Pituitary hormones alpha subunit identical

A
  • TSH
  • FSH
  • LH
  • hCG
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8
Q

Pituitary hormones Beta subunit differ by 30 AA

A
  • LH and hCG
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9
Q

Corpus luteum

A
  • Cyst that stays behind in the ovary made up of the granulosa cells which upon ovulation switch from making estrogen to progesterone for a limited time
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10
Q

FSH

A
  • Stimulates growth of a cohort of antral follicles and granulosa cell proliferation
  • Upregulate FSH and LH receptors (FSH turns on the LH receptor so the egg can “hear” when the LH comes around)
  • Stimulates aromatase activity in granulosa cells
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11
Q

Aromatase

A
  • Enzyme in granulosa cells of the follicle which convert androstenedione to estradiol (Converts testosterone to estradiol)
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12
Q

LH surge effects

A
  • Oocyte in dominant follicle completes meiosis 1 and releases 1st polar body (egg then arrests in metaphase II)
  • Increase in local secretion of plasminogen activator and cytokines required for ovulation
  • Release of oocyte from the follicle 36 hours after beginning of LH surge
  • Even before oocyte is released, granulosa cells around it begin to switch from producing estrogen to progesterone
  • Progesterone slows LH pulses/ decreases LH pulse freq.
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13
Q

Chance of getting pregnant at peak fertility

A
  • Peak fertility at ~25 years of age is 25%
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14
Q

LH surge trigger

A
  • Mid menstrual cycle when the follicle is ~20mm, estradiol secretion rises and stimulates the anterior pituitary
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15
Q

The ovary as an endocrine organ

A
  • Secretes estrogen and progesterone
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16
Q

What surrounds the oocyte in ovarian follicles

A
  • Somatic cells; granulosa and theca cells
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17
Q

Dominant follicle

A
  • Selected for each month to become a mature egg from a cohort of antral follicles
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18
Q

Follicle/oocyte count at each stage of a females development

A
  • 20 weeks gestation: 7,000,000
  • Birth: 1,000,000
  • Puberty: 300,000
  • Menopause: 0
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19
Q

Egg selection process

A
  • Eggs are selected for ~3 months prior to ovulation by unknown means
20
Q

Primordial follicle

A
  • 1 egg surrounded by 1 layer of granulosa cells (eggs of the future)
  • Arrested in meiosis I
  • Develop into Primary follicles
  • FSH and LH independent growth
21
Q

Primary follicles

A
  • Developed primordial follicles which are larger
  • FSH and LH independent growth
22
Q

Secondary follicle

A
  • Become early antral follicles after having developed from primary follicles
  • Transition phase in follicular development from having FSH and LH independent growth to being responsive to them
23
Q

Early antral follicles

A
  • Developed from secondary follicles to become Graafian or mature follicles
  • Can finally be seen on ultrasound
  • Start to accumulate fluid around the egg
  • FSH and LH responsive growth
24
Q

Graafian follicle

A
  • Mature follicle that has developed from early antral follicles
  • Thick layer of granulosa cells, fluid in middle and a specific set of cells surrounding the egg called cumulus cells
  • What is released upon ovulation along with cumulus cells
  • FSH and LH responsive growth
25
Q

Menstrual Chart

A
26
Q

Follicular growth process

A

Primordial —> Primary —> Secondary —> Early antral —> Graafian

  • Primordial - early antral: 85 days
  • Early antral - graafian: 14 days
  • 3 months to develop the egg that is to be released
27
Q

Cumulus cells

A
  • Egg itself is transcriptionally inactive; cumulus cells provide transcription making RNA for egg for the first 3 days post fertilization (after which the embryo has to turn on its own genome)
28
Q

What stage of meiosis is the oocyte in follicle arrested in?

A
  • First meiotic prophase (DNA has not been cut in half yet)
29
Q

What stage of meiosis is the released egg in?

A
  • Metaphase II
30
Q

Early follicular phase regulation

A
  • Release from neg. feedback effects of estrogen + progesterone —> increase in GnRH pulse frequency in early follicular phase - Increasing GnRH pulse —> 30% increase in serum FSH conc. - FSH release from the pituitary stimulates growth of a cohort of antral follicles - Ovary increasingly hormonally active —> rising serum estradiol and relatively low progesterone
31
Q

Follicular phase regulation

A
  • The follicle produces estrogen in a 2-cell process *Theca interna cells produces androstenedione in response to LH stimulation *FSH stimulates aromatase activity in granulosa cells- stimulating conversion of androstenedione —> estradiol - By late follicular phase, a single dominant follicle has been selected - Estrogen causes the uterine lining to thicken/ proliferate - Estrogen (and inhibin) result in neg. feedback to suppress pituitary FSH - Serum estradiol conc. peaks approx 1 day before ovulation - Once estradiol reaches a threshold estrogen feedback becomes stimulatory and results in LH surge: GnRH pulse frequency increases —> rise in LH
32
Q

How to clinically measure whether a women has ovulated

A
  • LH surge occurs over ~12hr period, most times we cannot catch this to measure So, we measure progesterone levels
33
Q

1st polar body

A
  • Created after the LH surge
34
Q

Cholesterol to Estrogen biosynthesis graph

A
35
Q

Early follicular phase regulation

A
  • Release from neg. feedback effects of estrogen + progesterone —> increase in GnRH pulse frequency in early follicular phase
  • Increasing GnRH pusle —> 30% increase in serum FSH conc.
  • FSH release from the pituitary stimulates growth of a cohort of antral follicles
  • Ovary increasingly hormonally active —> rising serum estradiol and relatively low progesterone
36
Q

Follicular phase regulation

A
  • The follicle produces estrogen in a 2-cell process

*Theca interna cells produce androstenedione in response to LH stimulation

*FSH stimulates aromatase activity in granulosa cells- stimulating conversion of androstenedione —> estradiol

  • By late follicular phase, a single dominant follicle has been selected
  • Estrogen causes the uterine lining to thicken/proliferate
  • Estrogen (and inhibin) result in engative feedback to suppress pituitary FSH and GnRH
  • Serum estradiol conc. peaks approx. 1 day before ovulation
  • Once estradiol reeaches a threshold estrogen feedback becomes stimulatory and results in rise in LH
37
Q

How to measure if a women has ovulated

A
  • LH surge occurs over ~12hr period of time; most times we cannot catch this in a lab setting to measure
  • Since we cant measure LH we must measure progesterone to determine if ovulation has occurred
38
Q

Hormonal chart

A
39
Q

Peak fertilization

A
  • After ovulation the egg survies for 1 day
  • Peak fertility is when a women is having an LH surge and sperm is present in the fallopian tube (where fertilization occurs)
  • Fertilization must occur within 24hrs of ovulation or ovum degenerates
  • 5 days later the egg reaches the uterus and has 18hrs to implant
40
Q

Length of time from egg (ovum) release to reaching uterus

A
  • 3-4 days
41
Q

If fertilization does not occur

A
  • Corpus luteum degenerates after ~14hrs
  • Estrogen and progesterone levels fall
  • Withdrawal of progesterone causes secretory endometrium to slough
  • As estradiol falls, FSH levels slowly rise again in absence of negative feedback —> menstruation
42
Q

Inhibin-B regulatory effects

A
  • decreases FSH (follicular phase)
43
Q

Inhibin-A regulatory effect

A
  • Decreases FSH (luteal phase)
44
Q

Activin regulatory effects

A
  • Increases FSH
45
Q

Progesterone regulatory effects

A
  • Decreases FSH, LH
46
Q

Inhibin

A
  • Inhibits FSH secretion and FSH actions
  • Blocks FSH synthesis and secretion in pituitary
  • Decreases pituitary GnRH receptors
  • Increases LH receptors on theca cells
47
Q

Activin

A
  • Functions locally in pituitary and ovary to augment FSH actions
  • Increases FSH receptors and GnRH receptors
  • In ovary increases FSH stimulation of aromatase and increases androgen production

RGU Exam 1 (14 decks)

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