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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

A

300,000

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
Q

summarise follicular growth

A

initial growth is independent of hormones and takes 85 days

final growth is dependent on FSH and takes 10 -14 days

26
Q

what does the LH surge cause in ovulation

A

prostaglandin endoperoxidase synthase in granulosa cells - pseudo inflammatory response

27
Q

what is the role of FSH in ovulation

A

stimulates plasminogen activator from granulosa cells which converts plasminogen to plasmin

28
Q

what do prostaglandins E and F do

A

release lysosomal enzymes that digest the follicular wall

29
Q

what is stigma

A

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
Q

describe formation of the corpus luteum

A

• 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
Q

what does the corpus luteum secrete

A

oestrogen, progesterone and inhibin

32
Q

what happens to the corpus luteum if no fertilisation

A

CL degenerates after 10 days by apoptosis

33
Q

what happens during the follicular phase

A

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
Q

what is inhibin

A

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
Q

name the layers of the primordial follicle going from outside to in

A

theca
granulosa
zona pellucida
oocyte

36
Q

when does the first polar body appear

A

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
Q

when does the second polar body appear

A

when the secondary oocyte is fertilised meiosis 2 completes and a polar body and zygote is formed

38
Q

when are primary oocytes formed

A

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
Q

how many oogonia are formed

A

7 million but most degenerate before birth

by puberty only 400,000 remain

40
Q

describe a primordial follicle

A

single layer of granulosa cells

secretes AMH

41
Q

describe a primary follicle

A

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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