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4/ RED > Ovarian Function > Flashcards

Ovarian Function Flashcards

1
Q

Describe the formation of the female reproductive system pre 7 weeks

A

Development is indifferent before 7 weeks - same as males
PGCs give rise to the gametes
Appear around week 3 in the epithelium of the yolk sac
Weeks 3-7:
- proliferate by mitosis
- migrate by amoeboid movement to region of dorsal wall that will form the gonads (genital ridges)
- migration is guided by chemotaxis

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2
Q

What determines development post 7 weeks?

A

no SRY gene –> female gonads develop

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3
Q

Describe the formation of the ovary

A
  • same influences of cells as seen in males
  • sex cord cells do not penetrate deeply, closer around oogonia (PGC) –> primordial follicles –> granulosa
  • mesonephric cells - vasculature/thecal cells
  • there is no endocrine activity during ovarian development in the female foetus
  • further developement is dependent on the presence of normal germ cells
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4
Q

What happens to ovaries in turners syndrome?

A

XO karyotype
normal oocyte developement reuiqres both X chromosomes –> oocyte death
- normal ovary development requires normal germ cells –> ovarian dysgenesis

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5
Q

How are adult ovaries different? x2

A

produce oocytes

produce hormones

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6
Q

What is the sequence of oogenesis in terms of cell names?

A 
primordial germ cell
oogonium
primary oocyte
secondary oocyte
mature/tertiary oocyte
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7
Q

What is the timing of entry into meiosis in males and females?
What is this controlled by?

A

males = meiosis is initiated post puberty
females = oogonia enter mouses during fatal period -controlled by Stimulated by retinpic act 7 gene (Stra8) retinoic acid
Cytochrome P450 mediated metabolism of RA
IN FEMALES
- during foetal period retinoic acid builds up, activates Stra8 and initiates meiosis
IN MALES
- meiosis isn’t until after puberty so cytochrome P450 metabolises retinioic acid so not enough to activate Stra8 gene

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8
Q

Oogenesis is not continuous.

Describe the two mieotic blocks

A

Primary oocyte is arrested at Prophase I (in utero)
Secondary oocyte is arrested at Metaphase II (puberty)
Meiosis completed post-fertilisation

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9
Q

Females are born with a finite number of oocytes, why?

A

all oogonia enter meiosis before birth - no ovarian stem cells

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10
Q

Female germ cells undergo clonal expansion then reduction (atresia?
When are there the most?

A

Proliferation up to 6 months after conception
Then apoptosis from then til menopause
Also ovulation depletes stores

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11
Q

Meiotic devisions are assymetrical

Describe how

A

Each meiotic division leads to production of a polar body

  • both are relativity small and contain little cytoplasm
  • excess genetic material being discarded by the egg
  • 1st polar body is released just before ovulation
  • presence of 2nd polar body signifies fertilisation and the complete of 2nd meiotic division
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12
Q

What are the two somatic cells in the follicles?

A

granulosa and theca

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13
Q

What are the stages of follicular development?

A

primordial follicle
primary follicle
secondary follicle
graafian follicle

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14
Q

Describe the primordial follicle

A

Primary occyte surrounded by single layer of flattened granulosa (foetus)
From puberty, a few primordial follicles begin to grow each death
- oocyte begins to grow and synthesises proteins needed for oocyte maturation and first few days of development post-fertilisation
- independent of menstrual cycle

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15
Q

Describe the primary follicle

A
  • granulosa cells become cuboidal; theca and zona pellucida become visible
  • independent of menstrual cycle
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16
Q

Describe the formation of the zona pellucida

A

Glycoprotein layer
granulosa cell-processes traverse through into the oocyte
ZP is important for sperm binding, induction of acrosome reaction and protection of the early embryo

17
Q

Describe the secondary follicle

A
  • granulosa proliferate; theca forms two distinct layers - internal and externa (5-15 follicles per cycle)
  • dependent on menstrual cycle
18
Q

Describe the tertiary follicle

A
  • Granulosa secrete follicular fluid
  • oocyte surrounded by laser of corona radiate and on stalk of cumulus cells; only 1 dominant follicle/cycle
  • dependent on menstrual cycle
19
Q

Describe/Draw the fluctuations in hormones during the menstrual cycle

A 
FSH = rises then falls during preovualtory phase, peaks at ovulation then decreases post ovulation 
LH = low until peak at ovulation 
Oestrogen = rises pre ovulation, peaks just before LH peak, then decreases post ovulation 
Progesterone = low until post ovulation where is reins then falls (menses)
20
Q

Describe extra-ovarian hormonal action (HPGaxis)

A

From puberty
- hypothalamus =pulsatile GnRH
Anterior pituitary
- FSH - acts on ovary FSHR, stimulates development of follicles
- LH - acts on ovary - LHCGR, stimulates follicle maturation, ovulation and development of corpus luteum

21
Q

Describe the functions of the ovarian hormones
Progesterone
Oestrogen
Cytokines

A

Oestrogens
- growth of body and sex organs at puberty
- development of secondary sexual characteristic
- Reproduction: follicle maturation, preparation of endometrium for pregnancy - proliferation
- Thinning of cervical mucus
Progesterone
-produced by corpus lutes
- acts on uterus - completes perparation and maintains endometrium for pregnancy
Numerous Cytokines

22
Q

What is the two cell hypothesis for oestrogen production?What is the role of LH and FSH

A

Testoterone is produced by theca cells and diffuses to granulosa where it is converted to oestrogen by aromatase

  • LH increases cholesterol uptake by the theca
  • FSH increases aromatase activity
23
Q

What occurs in the follicular/proliferative phase of the menstrual cycle

A
  • hypothalamus secrete GnRH
  • a. pituitary secretes FSH
  • up to 15 follicles are ‘rescued’
  • granulosa and theca cells develop in growing follicle
  • produce oestrogen (thickens endometrium/thins cervical mucus)
  • oestrogen suppresses FSH production
  • granulosa in dominante follicle expresses LHCG receptor
  • high levels of oestrogen at mid cycle causes LH surge from a. pituiary
24
Q

Describe what occurs during ovulation

A
  • Resumption and completion of Meiosis I
  • Secondary oocyte entered meiosis II arresting at metaphase
  • increase in follicular fluid and number of granulosa
  • cumulus oophorus loosens
  • follicle wall weakens - MMPs, plasminogen, collagenase, gelatinase
  • ovulation - oocyte, ZP, cumulus
  • cumulus-oocyte complex picked up by timbre of uterine tube
  • 30-36 hours
25
Q

Describe what happens during the luteal/secretory phase

A
  • corpus luteum formed
  • granulation - large lutein cells - progesterone and oestrogen
  • theca - many disperse to stromal tissue - small lutein cells - progesterone and androgens - LHCGR
  • endometrium becomes secretory
  • negative feedback - progesterone and oestrogen, LH/FSH levels low
26
Q

Describe what happens during pregnancy

A
  • trophoblast cells of embryo produce hCG - binds LHCGR on lutein cells maintains the corpus luteum
  • produces progesteron and oestrogen to support pregnancy
  • oestrogen/progesterone suppresses ovulation
  • 6/40 weeks - placenta takes over and the corpus lute degenerates –> corpus albicans
27
Q

What is luteolysis?

A
  • around 12 days - if there is not hCG production from an embryo, the corpus luteum degenerates forming the corpus albicans
  • progesterone and oestrogen levels fall, removing negative feedback and the cycle recommences

4/ RED (19 decks)

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