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Week 1 SEM 4 > Folliculogenesis > Flashcards

Folliculogenesis Flashcards

1
Q

What needs to be achieved to reproduce?

A

differentiation into male and female in embryo stage
sexual maturation (puberty)
good production, storage and release of egg/sperm
right chromosome number

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2
Q

What are the primordial germ cells the origin of (what do the PGC’s become)?

A

egg and sperm

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3
Q

3 weeks after conception, where is the primordial germ cell seen?

A

in the yolk sac of the foetus

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4
Q

What do the primordial germ cells do in the yolk sac of the foetus?

A

divide by mitosis to increase its number

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5
Q

After mitosis of the primordial germ cells, where do they go?

A

from yolk sac to genital ridge

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6
Q

What does the genital ridge form?

A

gonads

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7
Q

What is the word for primordial germ cells?

A

bipotential- they can become egg or sperm

when they reach the genital ridge form, then they can become egg or sperm accrording to the gonad formed

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8
Q

When the germ cells enter an ovary, what do they become?

A
  1. they become oocyte
  2. primordial germ cells colonize the area
  3. divide by mitosis
  4. then becomes oogonia (diploid)
  5. oogonia colonizes the ovary
  6. oogonia makes mitosis stop and meiosis begin
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9
Q

What is an oogonia?

A

egg precursor
have 46 chromosomes
multiply by mitosis- 7,00,000 formed

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10
Q

What does the oogonia do?

A

colonizes the ovary

mitosis stops and meiosis begins

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11
Q

At what stage does the oogonia arrest and what are they known as?

A

when oogonia enters first stage of meiosis, it arrests

known as primary oocytes

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12
Q

Till when does the primary oocyte remain arrested?

A

arrested in meiosis I (anaphase) till ovulation

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13
Q

Women have defined fertility/ true ovarian reserve. What does this mean?

A

=Women are born with all the eggs they will ever have

=eggs are laid down in foetal life

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14
Q

Why are mitotic divisions important?

A

The number of mitotic divisions will define how many eggs are laid down in the female ovary

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15
Q

At menopause, how many eggs will the female have left?

A

1,000

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16
Q

What happens in oogenesis?

A
  1. oogonia replication by mitosis
  2. forms primary oocytes
  3. when reach ovary, mitosis stops and meiosis begins
  4. arrest in first stage
  5. during LH surge and ovulation, meiosis I completes.
  6. meiosis arrests again at second stage (MEIOSIS II)
  7. after egg fertilises, meiosis II finishes
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17
Q

When is meiosis I complete?

A

ovulation

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18
Q

When is meiosis II complete?

A

after the egg fertilises

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19
Q

Before mitosis, how many chromatids are there per chromosome?

A

1
After replication there are 2 chromatids per chromosome
after mitosis, one chromatid per chromosome

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20
Q

What are spindles formed from?

A

centrioles

21
Q

Where are primary oocytes packed in the ovary?

A

outer layer of the ovary (cortex)

22
Q

What is a primordial follicle?

A

the oocyte needs to be protected
so is surrounded by protective layers and cells
the follicle comprises of granulosa cells
these granulosa cells secrete an acellular layer (no cells) around the oocyte called the basal lamina

23
Q

What do the granulosa cells do to protect the primordial follicle?

A

these granulosa cells secrete an acellular layer (no cells) around the oocyte called the basal lamina

24
Q

What is folliculogenesis?

A

growth and development of follicles at puberty from the earliest resting stages as laid down in the foetus through to ovulation

25
Q

What happens as the follicles start to grow?

A

granulosa cells multiply
shape become cuboidal
oocyte also grows in size

26
Q

What is the zona pelucida?

A

oocytes secrete a protective acellular layer

REMAINS attached to oocyte after ovulation

27
Q

What is the zona pelucida made of?

A

proteins ZP1, 2, 3

28
Q

What are theca cells?

A

once the follicle grows, there is another layer of cells differentiate around basal lamina

29
Q

What is the order of protection outside the oocyte?

A

OOCYTE, ZONA PELUCIDA, GRANULOSA CELLS, BASEMENT LAMINA, THECA CELLS

30
Q

What happens to the growth of the follicles if on the contraceptive pill?

A

the follicles continue to grow but die later bc later growth is dependent on FSH

31
Q

What happens when follicles start to grow?

A

diameter increase
granulosa cell division
gaps form in granulosa cell layer (consist of fluid spaces forming antrum)

32
Q

What are the fluid spaces in the granulosa called and filled with?

A

antrum

follicular fluid

33
Q

What are the 2 stages of follicle growth?

A

pre antral follicle growth

antral follicle growth

34
Q

What happens when the antrum continues to grow?

A

continues to grow
pushes some of the cell to the edge of the follicle
granulosa cells on the edge known as mural granulosa cells

35
Q

Where are the cumulus granulosa cells?

A

the ones surrounding the egg

36
Q

When the egg ovulates, what leaves the ovary and what is left?

A

cumulus oocyte complex leaves (CUMULUS GRANULOSA CELLS AND THE EGG)
WHAT IS LEFT= mural granulosa, theca cells and basal lamina

37
Q

To develop an antral follicle, what does it need to be under the influence of?

A

FSH

38
Q

How long does the initiation, recruitment, and selection of the follicle take?

A

90 days to occur

39
Q

What kind of blood supply does a follicle have?

A

avascular until theca cells form

40
Q

What steroid does the theca cell produce?

A

progestogens and androgens derived from cholesterol and is under the influence of LH

41
Q

What receptors do theca cells have?

A

LH

42
Q

How does oestrogen influence granulosa cells?

A

to drive granulosa cell proliferation

43
Q

What is aromatase influenced by?

A

FSH

44
Q

What receptors do granulosa cells have?

A

FSH

they acquire LH receptors in the dominant follicle

45
Q

What is the 2 cell, 2 gonadotrophin theory?

A
  1. Initially theca cells produce progestogens and androgens in response to LH
  2. androgens are converted into oestrogen in the granulosa cells in response to FSH
  3. dominant follicle acquires LH receptors and starts responding to LH and produces progestogens in the later stages
46
Q

What is the graafian follicle?

A

The single selected follicle will then grow very massively into the Graafian follicle.

47
Q

What happens in the 2 cell, 2 gonadotrophin theory?

A
  1. LH binds to LH receptors and stimulates androgen and progesterone production FROM CHOLESTROL
  2. Androgens enter the circulation and either go into circulation (deep) or go into granulosa cells
  3. In granulosa cells= convert to oestrodiol by aromatase
  4. Aromatase is stimulated by FSH binding to its receptor
48
Q

What is aromatase stimulated by?

A

FSH binding to receptor

49
Q

Explain the different LH and FSH receptors and where they go?

A

FSH receptors on granulosa cells (androgen to oestrodiol)

LH receptors on theca cells (cholestrol to androgens)= NEVER HAS FSH receptors

THE FOLLICLE which becomes destined ovulating follicle (dominant) acquires LH receptors on granulosa cells

Week 1 SEM 4 (7 decks)

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