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Histology and Physiology Reproduction System > Ovaries and Ovarian Cycle > Flashcards

Ovaries and Ovarian Cycle Flashcards

1
Q

what do the ovaries produce?

A

oocytes

sex steroids = estradiol and progesterone

protein hormones = relaxin, inhibin, and activin

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2
Q

gamete numbers at

birth, childhood, reproductive years, and menopause

A

birth = 1 million primordial follicles at prophase I of meiosis

childhood = over half lost through atresia, there are around 400,000 primordial follicles at puberty

reproductive years = ~1,000 lost per cycle through ovulation and atresia

menopause = 1000 primordial follicles

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3
Q

phases of the ovarian cycle

A

follicular = days 1-14

ovulation = day 14 and 15

luteal = days 15-28

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4
Q

when does luteal regression start?

A

day 24

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5
Q

when do variations occur in the ovarian cycle

A

only follicular phase

luteal phase is always constant 14 days

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6
Q

ovarian cycle is under what type of control

A

hormonal

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7
Q

dominant pituitary hormone during follicular phase

A

FSH (stimulated by GnRH)

stimulates progression from primordial follicle –> follicle –> ovulation

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8
Q

dominant pituitary hormone during luteal phase

A

LH (stimulated by GnRH)

stimulates development and degeneration of corpus luteum after ovulation

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9
Q

stages of follicular development

A
  1. primordial
  2. early preantral
  3. late preantral
  4. antral
  5. pre-ovulatory or Graafian follicle
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10
Q

cell types of the follicle

A

oocyte = egg itself

granulosa = cells that surround the oocyte, epithelial in origin

theca = outermost cell layer, more fibroblast in origin

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11
Q

chromosome number follicular stages

A

primordial = primary oocyte (46, 4n), meiosis I

primary = primary oocyte (46, 4n), meiosis I

secondary = primary oocyte (46, 4n), meiosis I
- zona pellucida is present

Graafian = secondary oocyte (23, 2n), metaphase of meiosis II
- zona pellucida present

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12
Q

Histology of the ovary

A

consists of a cortex and medulla

lining the cortex is a single layer of germinal epithelium
–> with many primordial follicles visible deep to it in the cortex

multiple stages of follicular development can be visulaized simulataneous in one image

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13
Q

histology of the primary follicle

A

multilaminar….if only 1 layer of granulosa cells it could be a primordial follicle

no opening or antrum between the oocyte and granulosa cells

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14
Q

histology of the secondary follicle

A

with proliferation of granulosa and theca cells (due to FSH)
…we see polarization of the oocyte towards one side and the formation of a cavity (antrum)

the theca divides into

  1. theca interna (hormone production)
  2. theca externa (structural)

zona pellucida appears

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15
Q

histology of secondary oocyte

A

Cumulus oophorus (CO) = granulosa cells surrounding the oocyte

Corona Radiate = first layer of granulosa cells in the CO that touch the ZP maintained at ovulation

there is communication between the oocyte and corona radiata through the ZP (cell processes of CR cells are sent through the ZP)

zona pellucida = protein rich gel secreted by the oocyte

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16
Q

mature Graafian follicle histology

A

the follicle that is picked for ovulation

similar in appearance to secondary follcile

can extend through the whole thickness of the cortex

the is a endocrine organ!!!!

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17
Q

Follicular atresia

A

vast majority of follicles undergo atresia via apoptosis

begins at fetal life and continues past menopause

can occur to follicles in any stage

histologically –> will see breakdown and death of granulosa cells and the follicle will degenerate

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18
Q

hormonal regulation during majority of follicular phase

general

A

GnRH (hypothalamus)
FSH (pituitary)
estradiol (ovary) –> positive feedback on the hypothalamus GnRH release
inhibin B (ovary, specifically granulosa cells)

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19
Q

luteal phase

progesterone reduces levels of what hormones

A

FSH and LH

due to negative feedback on hypothalamus release of GnRH

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20
Q

LH surge

A

end of follicular phase right before ovulation

before this (FSH > LH)

leads to high occupancy of LH receptors on the theca cells

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21
Q

why is LH surge more than FSH surge right before ovulation?

A

granulosa cells produce inhibin B

which inhibits FSH production from gonadotrophs

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22
Q

why do we want to inhibit FSH at the end of follicular phase?

A

because it largely stimulates follicular development and you don’t need to stimulate another follicle development immediately before ovulation

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23
Q

loss of androgen receptors lead to what? after the LH surge

A

rapid decrease in estradiol production

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24
Q

what nuclei make GnRH in hypothalamus

A

arcuate and preoptic

release into primary capillary plexus in the median eminence

pulsatile secretion leads to onset of puberty

ovarian steroid hormones feedback to hypothalamus to regulate pulsatile release

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25
Q

GnRH in late follicular phase

A

pulse frequency increases

due to positive feedback of estradiol

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26
Q

GnRH in luteal phase

A

pulse frequency decreases

negative feedback of progesterone

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27
Q

other non-sex steroid hormones that regulate GnRH release

A

inhibit = dopamine, endorphins, melatonin, CRF

stimulate = NE

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28
Q

structure between FSH and LH

A

both alpha and beta subunits

beta subunits differ

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29
Q

relative amounts of FSH LH in

childhood

adult, reproductive

menopause

A

childhood = FSH>LH

reproductive = cycles of LH and FSH

menopause = surge in FSH and LH, FSH > LH again

30
Q

why surge in LH and FSH post menopause

A

decreased progesterone in menopause

so loss of negative feedback

31
Q

measurement of GnRH

A

too small amounts to measure directly

so measure by measuring levels of LH

male = 8-10 pulses/day with each pulse only a few minutes

female = dependent on time of cycle
–> pulsatile secretion of GnRH is required….continuous GnRH does not maintain LH/FSH

32
Q

FSH target during follicular phase

A

granulosa cells of primary follicile (not primordial stimulation since that occurs spontaneously)

33
Q

LH target during follicular phase

A

theca interna (early)

granulosa (late)

34
Q

FSH effect during early follicular phase

A

stimulates mitosis

induces FSH receptors and gap junctions

induces aromatase to produce estradiol

stimulates inhibin B synthesis in granulosa cells
–> this stimulates androgen production by theca interna and decreases FSH secretion

35
Q

LH effect during early follicular phase

A

targets theca interna

stimulates steroid (androgen) production

36
Q

FSH effect during late follicular phase

A

with elevated estrogen levels

induces LH receptors on granulosa cells –> low progesterone production

37
Q

LH effect during late follicular phase

A

targets granulosa cells to start luteinization and progesterone synthesis

LH surge = high occupancy of LH receptors on theca cells blocks androgen precurosors needed for estradiol synthesis

38
Q

Steroidogenesis of ovary

A

second function of ovary besides making oocytes

theca interna = LH stimulates androgen production
granulosa = FSH stimulates inhibib B and androgen synthesis

FSH stimulates aromatase…which converts androgens from theca interna to estradiol

big picture LH and FSH stimulate estradiol

positive feedback of estradiol creates LH surge

39
Q

major hormones of luteal phase

A

LH
progesterone
inhibin A
hCG

40
Q

stages of corpus luteum

A

corpus luteum of cycle

corpus luteum of menstruation

corpus albicans

corpus luteum of pregnancy

41
Q

LH effect on corpus luteum in luteal phase

A

maintains it…

forms from luteinization of granulosa and theca cells

42
Q

what hormone does the corpus luteum make

A

progesterone

provides negative feedback

43
Q

low FSH in luteal phase effect on granulosa cells

A

make inhibib A which further reduces FSH

44
Q

corupus luteum of the cycle

A

takes up the whole ovary

producing androgens

the major endocrine organ now

45
Q

why does LH drop in luteal phase

A

negaitve feedback of progesterone

corupus luteum is essentially signaling its own death

46
Q

nonfunctional corpus albicans

A

after corpus luteum starts to undergo apoptosis

47
Q

corupus luteum of pregnancy

A

hCG from the blastocyst acts like LH

maintaining the corpus luteum throughout the 1st trimester

producing hormones

48
Q

FSH effect on theca cells during luteal phase

A

NO effect

49
Q

LH effect on theca cells during luteal phase

A

early = increase steroidgenic enzymes and androgens

late = decrease androgens due to high occupancy of LH receptors

50
Q

inhibin B effect on theca cells during luteal phase

A

increase androgens

51
Q

FSH effect on granulosa cells during luteal phase

A

early = increase proliferation, FSH receptors, gap junctions, aromatase, inhibin B, estradiol

late = increase LH receptors

52
Q

LH effect on granulosa cells during luteal phase

A

late = increase luteinization progesterone

53
Q

inhibin B effect on granulosa cells during luteal phase

A

NO effect

54
Q

FSH effect on theca lutein cells during luteal phase

A

NO effect

55
Q

inhibin B effect on theca lutein cells during luteal phase

A

NO effect

56
Q

LH effect on theca lutein cells during luteal phase

A

increase LDL uptake

increase androgens

57
Q

FSH effect on granulosa lutein cells during luteal phaes

A

increase inhibin A

58
Q

LH effect on granulosa lutein cells during luteal phase

A

increase LDL uptake

increase progesterone and estradiol

59
Q

inhibin B effect on granulosa lutein cells during luteal phase

A

NO effect

60
Q

7 steps that can summarize the ovarian cycle

A
  1. after GnRH stimulates FSH and LH production –> FSH stimulates aromatase and estrogen production
  2. FSH increases inhibin B, increasing estrogen production further and providing negative feeback on FSH producing cells
  3. LH stimulates steroid synthesis from theca interna
  4. LH increase progesteron production and luteinization in granulosa cells (late)
  5. low FSH levels stimulate granulosa lutein cells to secrete inhibin A, reducing LH and FSH
  6. progesterone from corpus luteum provides negaitve feedback, decreasing GnRH
  7. low LH –> cell death –> corpus albicans
61
Q

ovarian cysts

A

fluid filled cavities that originate from unruptures Graafian follicles

62
Q

Polycystic ovarian syndrome

A

elevated androgens and LH but reduced FSH

result = bilateral ovarian enlargement with multiple follicular cysts

63
Q

ovarian tumor

A

origin can surface epithelium, oocytes, follicular cells, or stromal cells

64
Q

menopause

A

faiilure of ovarian follicles to develop

reduced estrogen/progesterone, and inhibin B (loss of negative feedback on hypo and pit)

estrogen deficiency = bone loss, hot flashes, increased coronary artery disease

increase FSH and LH

65
Q

oviduct

A

provides proper environment for fertilization

regions = fimbria, infundibulum, ampulla, ishtmus, intramural part

66
Q

components of oviduct wall

A

mucosa = simple ciliated columnar with secretory (peg) cells interspersed

peg cells = provide nutrients to secondary oocyte, spermatozza, and preimplantation embryo

lamina propria = highly vascular

muscularis = poorly defined layers, inner circular, and outer long

serosa = highly vascular, loose CT

67
Q

amulla vs. isthmus of oviduct

A

isthmus has more muscle and less lumen/folding

fertilization occurs in ampulla

68
Q

estradiol effect on oviduct

A

increases cilia and ciliary beat

stimulates secretory activity

increases vascularity of lamina propria

increases vascularity and contractility of muscularis

69
Q

progesterone effect on oviduct

A

max ciliary beat, stimulates secretory activity

decreases contractions of muscularis

70
Q

events at the time of fertiliztion in oviduct

A
  1. zona pellucida has receptors for sperm , starts the acrosome reaction
  2. cortical reaction prevents polyspermaia
  3. sperm entering nuclues intiates completion of meiosis 2 to form mature ovum and second polar body
  4. nuclei of ovum and sperm fuse –> zygote

Histology and Physiology Reproduction System (12 decks)

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