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Endocrinology > Ovarian function > Flashcards

Ovarian function Flashcards

1
Q

when does the PGCs first become visible?

A
  • first become visible after 3 weeks in the epithelium of yolk sac
  • expand by mitosis and migrate to the genital rides during weeks 3-7
  • remain indifferent until week 6-7
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2
Q

what occurs during week 7?

A
  • > absence of SRY expression female gonads develop
  • further dev is dependent on normal germ cells (XX)
  • not dependent on endocrine activity
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3
Q

what is the prime function of the ovaries ?

A
  • production of oocytes

- produce hormones which regulate the whole process

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4
Q

what are primordial germ cells?

A
  • earliest form of recognisable germinal cell
  • capable of infinite mitosis
  • migrate to genital ridge –> week 6/7 embryo development
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5
Q

briefly outline the life of the human egg

A

PGC (migration to genital ridge)–> oogonium (during embryogenesis) –> primary oocyte arrested at prophase 1 –> ovulation–> secondary oocyte arrested at metaphase 2 (+ polar body) –> fertilisation –> 1 haploid ovum + 3 polar bodies

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6
Q

list the 2 types of somatic follicular cells

A
  • granulose cells -> epithelia, these produce oestrogens and progestagens
  • theca cells (stromal) produce androgens and progestogens
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7
Q

what is a primordial follicle ?

A
  • a primary oocyte surrounded by a single layer of flattened granulosa cells
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8
Q

when does folliculogenesis occur ?

A
  • during puberty

- growth of the oocyte and production of proteins needed for maturation and development post fertilisation

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9
Q

what is atresia?

A
  • degeneration and resorption of follicles before they have reached maturity
  • very few oocytes and follicles survive ovulation
  • majority eliminated before birth
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10
Q

what are the signs of apoptosis in Graafian follicles `?

A
  • Pyknosis and fragmentation of chromosomes and also wrinkling of nuclear envelope of oocyte
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11
Q

what happens to the pre-antral follicle?

A
  • granulosa become cuboidal

- the theca and ZP start to become visible

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12
Q

what is the role of the zona pellucida ?

A
  • contains many holes to allow for communication with granulosa cells
  • is a glycoprotein layer composed of 4 main ZP proteins
  • ## granulosa cell processes traverse ZP and contact the oocyte –> essential for egg nutrition
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13
Q

why are the cumulus cells important?

A
  • involved in protection of the early embryo
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14
Q

what happens at the secondary follicle ?

A
  • G cells proliferate and become 3/6 layers deep secreting follicular fluid in the process
  • theca forms 2 distinct layers (Interna + externa)
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15
Q

what happens at the tertiary follicle ?

A
  • G cells continually secrete follicular fluid
  • oocyte surrounded by granulosa cells attached by cumulus oophorus
  • 1 dominant follicle secreted per menstrual cycle
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16
Q

list the order of stages that occur during folliculogenesis

A

primordial follicle growth–> primary(pre-antral) –> secondary (early antral) –> tertiary (pre- ovulatory)

17
Q

what is the action of FSH on the ovaries?

A
  • stimulates development of follicles

- secretion of estradiol and ovulation

18
Q

what is the action of LH on the ovaries?

A
  • stimulates follicle maturation and dev of corpus luteum

- secretion of estradiol and ovulation

19
Q

what is the role of 17b estradiol during puberty and menstrual cycle ?

A
  • growth of body + sex organs (p)
  • development of secondary sexual characteristics (P)
  • follicle maturation (M)
  • preparation/ thickening of endometrium for pregnancy (M)
  • thinning of cervical mucus (M)
20
Q

what roles does progesterone elicit ?

A
  • at the uterus it completes the preparation of endometrium for Pregnancy
  • at the breasts it stimulates development of mammary glands
21
Q

what occurs during the follicular phase?

A
  • follicular maturation
  • endometrial proliferation
  • oocyte release
22
Q

what occurs during the luteal phase ?

A
  • involves corpus lute

- endometrium is now prepared for blastocyst implantation

23
Q

what stage signifies no pregnancy ?

A

menses

24
Q

the menstrual cycle is?

A
  • oocyte maturation followed by endometrial growth
  • follicular phase then the luteal phase
  • cyclical process with different levels of hormone production signifying each stage
25
Q

what is the 2 cell hypothesis ?

A
  • occurs during follicular phase (neg feedback)
    • LH stimulates theca cells to produce androgens –> these androgens enter the neighbouring granulosa cells
      FSH stimulates granulosa cells (via aromatase) to convert androgen to oestrogen (oestradiol) –> helps thicken the endometrium and thins cervical mucus
26
Q

what occurs during the pre-ovulatory phase?

A
  • stimulation of ovulation
  • switching to +ve feedback by FSH/LH
    • Dominant follicle has the highest FSH receptor density
    • Granulosa cells in the dominant follicle express LH receptors
    • High levels of oestrogen at mid cycle stimulate the hypothalamus to release GnRH –> +ve feedback
    • Causes a surge in LH and FSH spike from the AG
27
Q

when do you see a surge in LH and FSH levels?

A

during the pre-ovulatory phase of the menstrual cycle

28
Q

what happens during the ovulation process ?

A
  • changes in the follicle
  • one dominant follicle secreted by ovaries
    • Increase in the number of granulosa cells and the accumulation of follicular fluid
    • Cumulus oophorus loosens
    • Follicle wall weakens
    • Proteases are produced
    • Increased osmotic pressure
    • Stigma forms —> all attribute to the process of ovulation
      LH and FSH levels fal
29
Q

what occurs during the luteal phase (post ovulatory)?

A
  • formation of the corpus lute um stimulated by large surge in LH
  • fibrin clot forms in ruptured follicle
30
Q

what Is the role of LH in the luteal phase?

A

LH helps maintain the corpus luteum

LH and FSH stimulate progesterone and oestrogen production

Increased progesterone and oestrogen maintain the endometrium

This limits the dev of a new follice

31
Q

what is luteolysis?

A
  • 12 days post ovulation
  • occurs if there is no hCG secreted by an implanting blastocyst -> corpus luteum degenerates forming the corpus albicans
32
Q

what happens to estrogen and progesterone levels during luteolysis?

A
  • levels fall removing the negative feedback on APG so the cycle can recommence -> cyclical process
33
Q

what happens if pregnancy occurs?

A
  • developing embryo produces hCG –> acts like LH to maintain the corpus luteum
34
Q

what occurs at 6-7 weeks?

A

the placenta takes over production of progesterone

Endocrinology (17 decks)

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