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MD3002 post MSA > oogenesis > Flashcards

oogenesis Flashcards

1
Q

what is a follicle composed of

A

one germ cell surrounded by endocrine cells

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2
Q

what determines age at puberty

A 
genetics
nutrition 
geographic location 
exposure to light 
body composition and fat 
exercise
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3
Q

what are the functions of the ovary

A

production of gametes during the fetal period
maturation of the oocyte
ovulation
secretion of oestrogen and progesterone (steroid) and inhibin (peptide)

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4
Q

what is the zona pellucida

A

the thick transparent membrane surrounding an ovum before implantation.

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5
Q

what are granulosa cells

A

cells that surround the ovum

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6
Q

what are theca cells

A

endocrine function

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7
Q

how long are the stages of the ovarian cycle

A

– follicular phase: av 15 d (range 9-23 days)
– ovulatory phase: 1-3 d - culminates with ovula:on
– luteal phase: 13 d - less variable than follicular

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8
Q

how big is a mature follicle

A
  1. 5 cm
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9
Q

when do oogonia develop

A

3 weeks post conception in the embryonic yolk sac

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10
Q

describe development of oogonia

A

start in the yolk sac at 3 weeks
then migrate to the ovarian cortex
then divide by mitosis to produce 7 million oogonia
at 8-10 week divide by meiosis

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11
Q

how many oogonia degenerate

A

2 million around birth

400,000 around puberty

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12
Q

what is the most common cytogenic abnormality

A

aneuploidy (abnormal number of chromosomes)

-down’s syndrome is the most common of these

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13
Q

describe oogenesis at ovulation

A

stimulated by LH
during ovulation meiosis continues from prophase 1 of the primary oocyte until two cells are produced- the secondary oocyte and the polar body
the secondary oocyte begins meiosis but is arrested in metaphase 2

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14
Q

list the differences between oogenesis and spermiogenesis

A
  1. In females, mito:c prolifera:on of oogonia occurs
    prior to birth. In males, spermatogonia proliferate
    only aber puberty.
  2. In females, meio:c divisions of oocyte produces only one
    mature ovum. In males, meio:c divisions of primary
    spermatocyte produces 4 mature spermatozoa
  3. In females, second meio:c division is completed
    only upon fer:liza:on. In males, the products of
    meiosis (sperma:ds) undergo substan:al
    differen:a:on in the maturing process.
  4. finite numbers of ova- no germ cells
  5. ova are immotile
  6. oogenesis is discontinous
  7. oogenesis is not dependent on steroid hormones initially
  8. oogenesis requires normal body temperature
  9. oogenesis begins at birth- spermiogenesis begins at puberty
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15
Q

what is the cumulus oophorus

A

the stalk made out of granulosa cells that attaches the oocyte to the outside of the follicle

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16
Q

describe a primordial follicle

A

single layer of granulosa cells

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17
Q

what are thecal cells formed from

A

differentiation of granulosa cells

18
Q

what hormone can be used to asses follicular ageing

A

anti mullerian hormone

because it is secreted by primordial follicles

19
Q

how many oocytes are lost per cycle

A
  1. independent of hormones
20
Q

how many oocytes are in a female at puberty

21
Q

how many days does it take to reach 3 layers of follicular cells

A

85 (3 cycles)

22
Q

what does FSH do

A

stimulates rapid development of follicles leading to ovulation or atresia

23
Q

describe how the follicle changes when stimulated with FSH

A

zona develops and encloses the oocyte
rapid mitotic division of follicular cells
antrum develops and fills with fluid

24
Q

what does LH do

A

activates the theca interna to synthesis androstenedione, the precursor for estradiol synthesis by granulosa cells

25
summarise follicular growth
initial growth is independent of hormones and takes 85 days | final growth is dependent on FSH and takes 10 -14 days
26
what does the LH surge cause in ovulation
prostaglandin endoperoxidase synthase in granulosa cells - pseudo inflammatory response
27
what is the role of FSH in ovulation
stimulates plasminogen activator from granulosa cells which converts plasminogen to plasmin
28
what do prostaglandins E and F do
release lysosomal enzymes that digest the follicular wall
29
what is stigma
forms on the surface of the follicle, balloons out, forms vesicle and ruptures- oocyte expelled facillitated by intrafollicular pressure and contraction of smooth muscle in theca
30
describe formation of the corpus luteum
• Mature follicle discharges its antral fluid and egg. – Collapses around antrum and undergoes rapid transforma:on. • Granulosa cells enlarge, and form gland-like structure ie CORPUS LUTEUM
31
what does the corpus luteum secrete
oestrogen, progesterone and inhibin
32
what happens to the corpus luteum if no fertilisation
CL degenerates after 10 days by apoptosis
33
what happens during the follicular phase
bleeding stars follicles develop one follicle becomes dominant and matures ovulation marks the end of the follicular phase and the start of the luteal phase
34
what is inhibin
a protein secreted by granulosa and sertoli cells in response to FSH and is responsible for negative feedback control of FSH from the pituitary
35
name the layers of the primordial follicle going from outside to in
theca granulosa zona pellucida oocyte
36
when does the first polar body appear
when the primary oocyte divides by meiosis into the secondary oocyte. this happens each month from puberty to menopause this is stimulated by LH
37
when does the second polar body appear
when the secondary oocyte is fertilised meiosis 2 completes and a polar body and zygote is formed
38
when are primary oocytes formed
at 8 -10 weeks gestation meiosis starts turning oogonia into primary oocytes but arrested at prophase 1, complete around birth found in cortex of ovary
39
how many oogonia are formed
7 million but most degenerate before birth by puberty only 400,000 remain
40
describe a primordial follicle
single layer of granulosa cells secretes AMH
41
describe a primary follicle
single layer of granulosa cells zona pellucida cytoplasmic processes across the zona allowing nutrients and chemicals to cross

MD3002 post MSA (66 decks)

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