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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
GnRH in late follicular phase
pulse frequency increases due to positive feedback of estradiol
26
GnRH in luteal phase
pulse frequency decreases negative feedback of progesterone
27
other non-sex steroid hormones that regulate GnRH release
inhibit = dopamine, endorphins, melatonin, CRF stimulate = NE
28
structure between FSH and LH
both alpha and beta subunits beta subunits differ
29
relative amounts of FSH LH in childhood adult, reproductive menopause
childhood = FSH>LH reproductive = cycles of LH and FSH menopause = surge in FSH and LH, FSH > LH again
30
why surge in LH and FSH post menopause
decreased progesterone in menopause so loss of negative feedback
31
measurement of GnRH
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
FSH target during follicular phase
granulosa cells of primary follicile (not primordial stimulation since that occurs spontaneously)
33
LH target during follicular phase
theca interna (early) granulosa (late)
34
FSH effect during early follicular phase
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
LH effect during early follicular phase
targets theca interna stimulates steroid (androgen) production
36
FSH effect during late follicular phase
with elevated estrogen levels induces LH receptors on granulosa cells --> low progesterone production
37
LH effect during late follicular phase
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
Steroidogenesis of ovary
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
major hormones of luteal phase
LH progesterone inhibin A hCG
40
stages of corpus luteum
corpus luteum of cycle corpus luteum of menstruation corpus albicans corpus luteum of pregnancy
41
LH effect on corpus luteum in luteal phase
maintains it... forms from luteinization of granulosa and theca cells
42
what hormone does the corpus luteum make
progesterone provides negative feedback
43
low FSH in luteal phase effect on granulosa cells
make inhibib A which further reduces FSH
44
corupus luteum of the cycle
takes up the whole ovary producing androgens the major endocrine organ now
45
why does LH drop in luteal phase
negaitve feedback of progesterone corupus luteum is essentially signaling its own death
46
nonfunctional corpus albicans
after corpus luteum starts to undergo apoptosis
47
corupus luteum of pregnancy
hCG from the blastocyst acts like LH maintaining the corpus luteum throughout the 1st trimester producing hormones
48
FSH effect on theca cells during luteal phase
NO effect
49
LH effect on theca cells during luteal phase
early = increase steroidgenic enzymes and androgens late = decrease androgens due to high occupancy of LH receptors
50
inhibin B effect on theca cells during luteal phase
increase androgens
51
FSH effect on granulosa cells during luteal phase
early = increase proliferation, FSH receptors, gap junctions, aromatase, inhibin B, estradiol late = increase LH receptors
52
LH effect on granulosa cells during luteal phase
late = increase luteinization progesterone
53
inhibin B effect on granulosa cells during luteal phase
NO effect
54
FSH effect on theca lutein cells during luteal phase
NO effect
55
inhibin B effect on theca lutein cells during luteal phase
NO effect
56
LH effect on theca lutein cells during luteal phase
increase LDL uptake increase androgens
57
FSH effect on granulosa lutein cells during luteal phaes
increase inhibin A
58
LH effect on granulosa lutein cells during luteal phase
increase LDL uptake increase progesterone and estradiol
59
inhibin B effect on granulosa lutein cells during luteal phase
NO effect
60
7 steps that can summarize the ovarian cycle
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
ovarian cysts
fluid filled cavities that originate from unruptures Graafian follicles
62
Polycystic ovarian syndrome
elevated androgens and LH but reduced FSH result = bilateral ovarian enlargement with multiple follicular cysts
63
ovarian tumor
origin can surface epithelium, oocytes, follicular cells, or stromal cells
64
menopause
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
oviduct
provides proper environment for fertilization regions = fimbria, infundibulum, ampulla, ishtmus, intramural part
66
components of oviduct wall
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
amulla vs. isthmus of oviduct
isthmus has more muscle and less lumen/folding fertilization occurs in ampulla
68
estradiol effect on oviduct
increases cilia and ciliary beat stimulates secretory activity increases vascularity of lamina propria increases vascularity and contractility of muscularis
69
progesterone effect on oviduct
max ciliary beat, stimulates secretory activity decreases contractions of muscularis
70
events at the time of fertiliztion in oviduct
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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