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GIGU > The Menstrual Cycle and Ovulation > Flashcards

The Menstrual Cycle and Ovulation Flashcards

1
Q

What do thecal cells lack that allows them to produce androstenedione?

A

Similar to Leydig cells, but lack 17B (prevents testosterone from forming androstenedione in Leydig cells)

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2
Q

What are granulosa cells similar to in males?

A

nurse Sertoli cells

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3
Q

Why are cumulus cells released with the oocyte during ovulation?

A

Critical for oviduct to grab onto the oocyte

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4
Q

What causes meiotic arrest in prophase I of oocytes?

A

stuck in prophase 1 of meiosis 1 d/t:
–>elevated cAMP levels

**have proteins to finish meiosis but cAMP maintains arrest until LH surge

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5
Q

What stimulates completion of meiosis I in oocytes?

A

LH surge

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6
Q

How long can an oocyte stay in the first meiotic arrest?

A

50 years

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7
Q

When does meiosis I finish?

A

a few hours before ovulation

  • ->expels 1st polar body
  • ->produces MAPK to arrest at metaphase II
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8
Q

What causes the second meiotic arrest in oocytes?

A

stuck in metaphase II d/t:

–>elevated levels of MAPK proteins

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9
Q

When does meiosis II resume and complete?

A

at fertilization only

  • ->rapidly degrades MAPK to finish
  • ->expels 2nd polar body
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10
Q

What is the functional unit of the ovary?

A

ovarian follicle

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11
Q

What is the primordial follicle?

A

primary oocyte arrested in prophase I
–>surrounded by single layer of pregranulosa cells

**only release paracrine factors, not steroid hormones

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12
Q

What represents the ovarian reserve?

A

primordial follicles

–>most undergo atresia

–>only 400-500 develop and ovulate over lifetime

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13
Q

Describe the primary follicle

A

central primary oocyte surrounded by single layer of cuboidal granulosa cells

–>increase in size d/t increase in growth of primary oocyte

–>produce ZP 1-4 as zona pellucida forms

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14
Q

Describe the secondary follicle

A

primary oocyte surrounded by 3-6 layers of granulosa cells

–>paracrine secretion induces stromal cells to form thecal cells

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15
Q

Describe the orientation of thecal cells in the secondary follicle

A

theca interna: highly vascular

theca externa: fibrous capsule-like

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16
Q

Describe changes that cause primary follicle to become secondary follicle

A
  • Follicles move closer to inner medulla of ovary (where vasculature is) and release angiogenic factors
  • ->develop 1-2 arterioles to generate vascular wreath around follicle

*Zona pellucida develops

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17
Q

What receptors do granulosa cells express?

A

FSH receptors

–>paracrine factors for oocyte growth

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18
Q

Do granulosa cells produce ovarian hormones in preantral follicles?

A

NO

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19
Q

What are thecal cells analogous to?

A

Leydig cells

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20
Q

What receptors do thecal cells express?

A

LH receptors

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21
Q

What is the major product from thecal cells?

A

androstenedione

–>minimal during preantral follicular period

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22
Q

What marks the beginning of the antral phase of follicular development?

A

appearance of antrum (space filled with fluid around oocyte)

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23
Q

What does increase in follicular size during the antral phase depend on?

A
  • increase in antral size
  • volume of follicular fluid
  • prolif of granulosa cells
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24
Q

What is the dense mass of granulosa cells that surrounds the oocyte suspended in fluid?

A

cumulus oophorus

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25
Q

What are the 2 distinct populations of granulosa cells in the antral phase/

A
  • mural granulosa (stratum)
  • –>outer wall of follicle, highly steroidogenic
  • cumulus cells (corona radiata)
  • –>maintain gap and adhesion jxns with oocyte
  • –>released during ovulation with oocyte
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26
Q

What subset of granulosa cells make up the outer wall of the follicle and are highly steroidogenic?

A

mural granulosa

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27
Q

What gonadotropins are antral follicles responsive to during the antral phase?

A

FSH and LH

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28
Q

What do theca interna cells do in response to LH during antral phase?

A

synthesize androgens from acetate and cholesterol
–>major: androstenedione

–>limited estrogen synthesis

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29
Q

What do granulosa cells do in response to FSH during antral phase?

A

convert androgens from thecal cells
–>aromatization of androgens to ESTROGEN

–>induce expression of LH receptors in late follicular phase

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30
Q

When does oocyte growth slow?

A

rapid in early stages of antral follicles

slows in larger follicles

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31
Q

What follicular stage does oocyte complete meiosis I at ovulation?

A

antral stage

–>oocyte secrete cell cycle components

–>larger antral follicles still maintain meiotic arrest (via elevated cAMP) until LH surge

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32
Q

What are the 3 phases of the ovarian follicle cycle?

A

1: follicular phase
- –>preantral and antral sub-phases
2: ovulatory phase
3: luteal phase

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33
Q

How does sensitivity to FSH aid in selection of the dominant follicle?

A

FSH declines due to mural granulosa cells producing low levels of estrogen and inhibin B

  • ->largest follicle with most FSH receptors survives (becomes dominant)
  • ->other follicles undergo atresia
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34
Q

Describe how a dominant follicle is chosen

A

Each monthly cycle, several large antral follicles are recruited to begin development

–>all undergo atresia except 1 d/t FSH decline

–>dominant follicle (usually largest with lots of FSH receptors) chosen in early follicular phase

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35
Q

What does the midcycle dominant follicle become?

A

Graffian follicle (large preovulatory follicle)

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36
Q

What is the periovulatory period?

A

onset of LH surge to ovulation

–>32-36 hours

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37
Q

What is the fxn of the periovulatory period?

A

Prepare for ovulation:

  • ->changes in steroidogenic fxn of theca and mural granulosa
  • **prepare cell for luteinization
  • **formation of corpus luteum
  • ** increased production of progesterone
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38
Q

During the LH surge, what cells express LH receptors?

A

both thecal and mural granulosa cells

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39
Q

What reduces the positive feedback on LH secretion during the LH surge?

A

surge shifts steroidogenic activity so there is a transient inhibition of aromatase

  • ->reduces positive feedback on LH
  • ->switches production of estradiol to progesterone
40
Q

When is there an increase in progesterone production?

A

after LH surge/ovulation

41
Q

What is the consequence of increased vascularization of granulosa during LH surge?

A

increased cholesterol availability for progesterone production

42
Q

LH surge induces oocytes to?

A

progress to metaphase II

–>releases inhibition of the first meiotic arrest

43
Q

How does the LH surge affect structural changes in the follicle?

A

LH surge + release of cytokines and hydrolytic enzymes

–> breakdown of follice, wall, tunica albuginea, surface epithelium

–>allows cumulus-oocyte complex to detach so it’s free in the antrum

–>basal lamina of mural granulosa degradation to allow increased blood supply to corpus luteum (remainder of follicle without oocyte)

44
Q

What is the corpus luteum?

A

the remainder of the follicle after the cumulus-oocyte complex has been emitted

45
Q

What happens to the corpus luteum/follicle after the oocyte complex has been released?

A

antral cavity fills with RBC and debris
–>removed via macrophages

Granulosa lutein cells collapse into cavity

  • ->filled with cholesterol esters (progesterone), thecal cells, WBC
  • ->yellow in color d/t lutein pigment
46
Q

How long is the corpus luteum programmed to survive for?

A

14 days

47
Q

What happens when the corpus luteum is rescued by hCG?

A

will survive for remainder of pregnancy, main source of progesterone until placenta can take over

48
Q

What happens to the corpus luteum after 14 days and no hCG/pregnancy?

A

forms a collagen scar-like body called the corpus albicans

–>regresses to inner medulla of ovary, absorbed

49
Q

Why is progesterone from the corpus luteum important in early pregnancy?

A

transforms uterine lining into adhesive and supportive structure–> implantation

50
Q

Describe estrogen increase/decrease following LH surge

A

Transient decrease following LH surge

Then rebounds and peaks in midluteal phase

51
Q

What reduces LH to basal levels during pregnancy?

A

progesterone
estrogen
–compensation via hCG

52
Q

What secretes inhibin A? What is its function?

A

Lutein cells

suppress FSH in pregnancy so not continuously ovulating when pregnant

53
Q

Describe follicular atresia

A

Predominant process in ovary
–>occurs any time during development

*apoptosis of oocytes and granulosa cells

***thecal cells persist to repopulate cellular stroma of ovary

54
Q

What are collectively known as interstitial gland of ovary?

A

Thecal cells with LH receptors

55
Q

Describe the HP-ovarian axis

A

GnRH–> FSH and LH via gonadotrophs

FSH and LH + ovary to synthesize estrogens and progestins

56
Q

Do ovarian steroids exert negative or positive feedback on the HPO axis?

A

both

57
Q

Describe follicular response to GnRH

A

Early phase: gonadotrophs in pituitary not very responsive to GnRH
–>only small rise in LH

Late phase: very sensitive to GnRH–> larger release of LH

58
Q

What does LH act on after ovulation?

A

Corpus luteum

59
Q

What acts on the developing follicle before ovulation?

A

FSH and LH

  • ->both required for estrogen production
  • –>theca and granulosa cells can’t finish production independently
60
Q

What receptors do theca cells have?

A

LH

61
Q

What receptors do granulosa cells have?

A

FSH

some LH

62
Q

What cell products inhibins?

A

granulosa cells of follicle
–>activated by FSH and during LH surge

**inhibits FSH production in anterior pituitary

63
Q

What produces activins?

A

granulosa cells

***stimulate FSH from anterior pituitary

64
Q

Describe negative feedback of HPO axis via ovarian steroids

A

Estrogens and progestins

–>reduce LH and FSH release

**progestins only negative at high concentrations

**estrogens negative at any concentration

65
Q

Describe positive feedback of HPO axis via ovarian steroids

A

@ end of follicular phase
–>estradiol at certain level for 2 days causes HP axis to reverse sensitivity to estrogens

–>switch to positive feedback promotes LH SURGE

**progesterone late follicular phase also positive to help LH surge

66
Q

Describe negative feedback by inhibits on HPO axis

A

inhibit FSH secretion

67
Q

Describe positive feedback by activins on HPO axis

A

INDEPENDENT of GnRH

stimulate FSH release and ovarian synthesis of estrogens

68
Q

Is GnRH required to help activins stimulate FSH release?

A

NO

69
Q

What happens to FSH and LH as luteal phase of menstrual cycle begins?

A

rapidly decrease

–>negative feedback by estradiol, progesterone and inhibin (increase)

also causes ovarian steroid levels to drop

70
Q

What is the relationship of LH and FSH to ovarian steroids during the start of the luteal phase?

A

FSH and LH drop

Estradiol, progesterone and inhibin increase

71
Q

What leads to decreased ovarian steroids in late luteal phase?

A

demise of corpus luteum

72
Q

What happens to GnRH during menses?

A

HP axis returns to follicular-phase pattern

–>gradual increase in pulsatile GnRH

73
Q

What is the major product of the follicle during the follicular phase?

A

estradiol

–>aromatase, 17-20 and 17a absent

74
Q

What is required for estradiol synthesis in follicle cells?

A

theca cells

granulosa cells

75
Q

What is required for estradiol synthesis in corpus luteum?

A

theca-lutein cells

granulosa-lutein cells

76
Q

When are estrogens produced?

A

Follicular phase via follicles

Luteal phase via corpus luteum

77
Q

What are the major products of the corpus lutem during the luteal phase?

A

progestins

–>estradiol still substantial

78
Q

What does estrogen to to basal body temperature during the follicular phase of the menstrual cycle?

A

high levels of estrogen lower BBT

79
Q

What hormone raises BBT?

A

Progesterone released by corpus luteum post-ovulation

–>day after ovulation

80
Q

What does a drop in BBT coincide with?

A

no pregnancy and next menstruation cycle

–>d/t disintegration of corpus luteum

81
Q

Describe the menstrual phase of the endometrial cycle

A

degeneration–>bleeding
–>defined as day 1 of menstrual cycle

**d/t degeneration of corpus luteum (no preg–> decreased estrogen and progesterone)

82
Q

What is considered day 1 of menstrual cycle?

A

first day of bleeding/endometrial degeneration

83
Q

Describe the proliferative phase of endometrial cycle

A

restored after day 5 of cycle

–>prolif of basal stromal cells in zona basalis

–>” of epithelial cells from uterus

–>stroma gives rise to CT components of endometrium

–> +++ by estrogen fri developing follicles

84
Q

Describe estrogen levels in proliferative phase of endometrial cycle

A

rise early in follicular phase and peak just before ovulation

–> causes stromal components of endometrium to become highly developed

–> induces synthesis of progestin receptors in endometrial tissue

85
Q

Describe the secretory phase of the endometrial cycle

A

Final phase that c/t luteal phase of ovarian cycle

  • increase vasc of endometrium
  • endometrial glands are engorged with secretions

PROGESTERONE:
–>promotes diff of stromal cells into predecidual cells–> decidua of pregnancy

OR

–> helps menstruation in absence of pregnancy

86
Q

Describe the pathophysiology of PCOS

A
  • most common cause of infertility
  • adolescence
  • unexplained hyperandrogenism, anovulation, polycystic ovary
  • abnml steroidogenesis of ovary, folliculogenesis
87
Q

Describe hormone levels in PCOS

A

Elevated LH

Low FSH

Elevated testosterone

Increased DHEA d/t enlarged polycystic ovaries

***high androgens promote atresia of developing follicles, disrupt feedback

88
Q

What are presentations of PCOS females?

A 
obese
young
hirsutism
reproductive age
oligomenorrhea
infertility
89
Q

What is the most common cause of congenital hypogonasism?

A

Turner syndrome

–>complete absence of second X chromosome

90
Q

Describe Turner syndrome

A

missing x chromosome
——>45 X
primary hypogonadism

female int/ext genitalia

ovarian failure

elevated serum FSH

91
Q

What are common sx of Turner syndrome?

A 
short stature
delayed puberty
infertility
webbed neck
lymphedema of 
      hands/feet
learning disabilities
skeletal abnml
92
Q

Describe menopause

A

12 months after LMP
–>average 51 yrs

Reduction of estrogen and low levels of inhibin
–>no negative feedback of LH and FSH

High FSH and LH

93
Q

What are sx of menopause?

A 
irregular periods
vaginal dryness
hot flashes
night sweats
sleeping problems
mood changes
weight gain
slow metabolism
thinning hair
dry skin
lost of breast fullness
94
Q

What are tmts for the sx of menopause?

A
  • estrogen therapy
  • vaginal estrogen
  • low-dose antidepressants
  • Gabapentin for hot flashes
95
Q

What exert negative feedback to reduce LH and FSH?

A

estrogen

progestins

GIGU (37 decks)

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