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GIGU Final > Menstrual Cycle and Ovulation > Flashcards

Menstrual Cycle and Ovulation Flashcards

1
Q

the menstrual cycle can be broken down into 2 different cycles. What are they?

A

ovarian cycle and the endometrial cycle

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2
Q

what are the phases of the ovarian cycles?

A

follicular phase and the luteal phase

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3
Q

what are the phases of the endometrial phase?

A

menses, proliferative phase, and secretory phase

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4
Q

what is the primary hormone involved in the follicular phase?

A

estrogen

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5
Q

what is the primary hormone involved in the luteal phase?

A

progesterone

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6
Q

what stage of meiosis are the primordial germ cells in arrest at?

A

prophase I

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7
Q

what keeps the primordial germ cells in meiotic arrest?

A

elevated levels of cAMP

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8
Q

how long do the primordial germ cells stay in meiotic arrest in prophase I?

A

until the LH surge

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9
Q

where does the second meiotic arrest occur?

A

metaphase II

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10
Q

how does the second meiotic arrest in metaphase II occur?

A

elevated levels of MAPK proteins

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11
Q

when is there resumption of meiosis II?

A

only at fertilization

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12
Q

what is the functional unit of the ovary?

A

ovarian follicle

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13
Q

what happens in the follicle of the ovary?

A

gametes develop and mature

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14
Q

what is the primordial follicle surrounded by?

A

a single layer of pregranulosa cells

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15
Q

what does the primordial follicle represent?

A

the ovarian reserve

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16
Q

within the primordial follicle what type of oocyte would you find?

A

primary oocyte

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17
Q

what is the primary follicle surrounded by?

A

a single layer of granulosa cells- cuboidal shape

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18
Q

Besides the shape of the granulosa cells surrounding the primary follicle, what is another key feature of the primary follicle?

A

there is early production of secreted glycoprotein (ZP1-4)

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19
Q

within the primary follicle what type of oocyte would you find?

A

primary oocyte

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20
Q

what is the secondary follicle surrounded by?

A

3-6 layers of cuboidal granulosa cells

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21
Q

besides the multiple layers of granulosa cells surrounding the secondary follicle, what is another key feature of the secondary follicle?

A

there are now secretions of paracrine factors to induce local stromal cells to differentiate into thecal cells

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22
Q

the progression to a secondary follicle involves increased what?

A

vascularization

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23
Q

what do the secondary follicles release to increase vascularization?

A

angiogenic factors- induce the development of 1-2 arterioles

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24
Q

what does the induction of the development of 1-2 arterioles generate?

A

a vascular wreath

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25
Q

what are the preantral follicles dependent on for oocyte growth?

A

paracrine factors (the granulosa cells express FSH receptors)

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26
Q

when does the antrum begin developing?

A

during the secondary follicle stage

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27
Q

what is the term for when the oocyte is suspended in fluid surrounded by a dense mass of granulosa cells?

A

cumulus oophorus

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28
Q

what happens during the antral phase of follicular development?

A

there is a 100-fold increase in granulosa cells

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29
Q

what are the two distinct populations of granulosa cells that appear during the antral phase?

A

mural granulosa (stratum granulosum) and cumulus cells

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30
Q

when does growth of the follicle become responsive to gonadotropins?

A

at the antral follicle stage (late secondary stage)

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31
Q

what happens when LH interacts with its receptors on the theca interna cells?

A

they synthesize androgens

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32
Q

what do theca interna cells synthesize the androgens from?

A

acetate and cholesterol

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33
Q

what happens when the granulosa cells interact with FSH?

A

they will convert the androgens that are produced by the theca cells into estrogen

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34
Q

what is the reaction that converts androgens into estrogen?

A

aromatization

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35
Q

when does the oocyte become competent to complete meiosis I at ovulation?

A

at the antral stage

36
Q

what do the mural granulosa cells produce?

A

low levels of estrogen and inhibin B

37
Q

midcycle, what does the dominant follicle become?

A

a large preovulatory follicle (graffian follicle)

38
Q

what is the periovulatory period?

A

the time from onset of the LH surge to ovulation (32-36 hours)

39
Q

what occurs during the periovulatory period?

A

structural changes and changes in the steroidogenic function of the theca and mural granulosa

40
Q

what does the LH surge induce?

A

differentiation (luteinization) of granulosa cells to granulosa lutein cells

41
Q

what do the granulosa cells express at the time of the LH surge?

A

LH receptors

42
Q

during the luteinization, what are the granulosa cells inhibiting?

A

aromatase expression

43
Q

what does less aromatase expression result in?

A

a rapid decline in the androgens being converted into estradiol; this rapid decline reduces positive feedback on LH secretion

44
Q

what effect does the increased vascularization have on the granulosa cells during luteinization?

A

it increases the cholesterol availability for progesterone production

45
Q

How does the follicle wall, tunica albuginea, and surface epithelium breakdown?

A

through the release of cytokines and hydrolytic enzymes from theca and granulosa cells

46
Q

what is the antral cavity filled with during the luteal phase? and what is it called now (the transient stage between the follicle and the corpus luteum)

A

blood/ cell debris- called the corpus hemorrhagicum

47
Q

once the corpus hemorrhagicum is removed by macrophages, what is the antral cavity filled with?

A

granulosa lutein cells, cholesterol esters, theca cells, blood vessels, and white blood cells

48
Q

how long does the corpus luteum remain?

A

around 2 weeks

49
Q

what is the scar-like body that develops from the corpus luteum and what is it primarily composed of?

A

corpus albicans- primarily collagen

50
Q

what is the corpus luteum sensitive to?

A

HCG (similar in structure to LH)

51
Q

what happens if fertilization happens and the trophoblast begins secreting hCG?

A

the corpus luteum will continue producing progesterone

52
Q

what is the role of the progesterone produced by the corpus luteum during pregnancy?

A

it transforms the uterine lining into an adhesive and supportive structure

53
Q

why is the reduction of LH and secretion of inhibin by lutein cells (suppression of FSH) important if there is pregnancy?

A

it prevents the production of other follicles if there is pregnancy (so that there is not additional energy going into follicular development during pregnancy)

54
Q

how does atresia occur?

A

apoptosis (due to the decline of FSH)

55
Q

what happens to the thecal cells of follicles that have been apoptosed?

A

thecal cells persist and repopulate the cellular stroma of the ovary (known as the interstitial gland of the ovary)

56
Q

what do LH and FSH stimulate the ovary to do?

A

synthesize and secrete estrogens and progestins

57
Q

early in the follicular phase, what is the sensitivity like of the gonadotrophs to GnRH?

A

early in the follicular phase, gonadotrphs are not very GnRH sensitive; each burst of GnRH elicits only a small rise in LH

58
Q

later in the follicular phase, what is the sensitivity like of the gonadotrphs to GnRH?

A

later in the follicular phase, gonadotrophs in the anterior pituitary become much more sensitive to GnRH in the portal blood; each burst of GnRH triggers a much larger release of LH

59
Q

what enhances the sensitivity of the gonadotrophs to GnRH?

A

the high levels of estradiol that are typical of the late follicular phase

60
Q

theca cells have what type of receptors?

A

LH receptors

61
Q

granulosa cells have what type of receptors?

A

both LH and FSH

62
Q

what is required for estrogen production?

A

both LH and FSH are required

63
Q

after ovulation, what does LH act on?

A

the cells of the corpus luteum

64
Q

what is inhibin produced by in females?

A

the granulosa cells of the follicle

65
Q

what stimulates the granulosa cells to produce inhibins?

A

FSH; just before ovulation, after the granulosa cells acquire LH receptors, LH stimulates the production of inhibin by granuosa cells

66
Q

what is the action of inhibins in females?

A

it inhibits FSH production by gonadotrophs (this negative feedback loop is really necessary for selecting that dominate follicle)

67
Q

what is the role of activins?

A

they are produced in the same tissues as the inhibins but they stimulate FSH release from the pituitary cells

68
Q

what is the net effect of the estrogens and progestins feeding back to the hypothalamus and the pituitary>

A

to reduce LH and FSH release

69
Q

after the estradiol levels reach a certain threshold what happens to the HP axis?

A

it reverses its sensitivity to estrogens, it now exerts a positive feedback–> promotes the LH surge

70
Q

what is involved in the induction of the LH surge?

A

positive feedback of estrogens, progestins, and activins on the HP axis

71
Q

what happens to the LH and FSH levels as the luteal phase of the menstrual cycle begins?

A

they rapidly decrease

72
Q

what does the fall off of gonadotropin levels as the luteal phase of the menstrual cycle begins reflect?

A

negative feedback by estradiol, progesterone, and inhibin

73
Q

during the luteal phase, the rise in concentration of estradiol, progesterone, and inhibin causes what?

A

the continued decrease of gonadotropin levels midway through the luteal phase

74
Q

during the late luteal phase, the gradual demise of the corpus luteum leads to what?

A

decreases in the levels of progesterone, estradiol, and inhibin

75
Q

during the follicular phase, what is the major product of the follicle?

A

estradiol

76
Q

during the luteal phase, what are the major products of the corpus luteum?

A

progestins, although estradiol synthesis is still substantial

77
Q

what effect on the basal body temperature do the higher levels of estrogen present during the pre-ovulatory (follicular) phase of the menstrual cycle have?

A

they lower BBT

78
Q

what effect does the higher levels of progesterone released by the corpus luteum after ovulation have on basal body temperature?

A

they raise BBT

79
Q

when can the rise in BBT most commonly be seen?

A

the day after ovulation

80
Q

if the oocyte was not fertilized and pregnancy did not occur in the previous cycle, what causes the demise of the corpus luteum?

A

a sudden diminution in estrogen and progesterone secretion

81
Q

what is the proliferation and differentiation of the endometrium during the proliferative phase stimulated by?

A

estrogen (which is secreted by the developing follicles)

82
Q

what causes the induction of the synthesis of progestin receptors in the endometrial tissue?

A

estrogen

83
Q

what promotes the differentiation of the stromal cells into predecidual cells?

A

progesterone

84
Q

when is the average age of menopause?

A

51.4 years of age

85
Q

what is menopause caused by?

A

there is a reduction in estrogen, so there are low levels of inhibin; there is no negative feedback of LH and FSH, therefore there are high levels of LH and FSH seen with menopause

GIGU Final (15 decks)

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