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Reproduction > Folliculogenesis > Flashcards

Folliculogenesis Flashcards

1
Q

What are the 4 things required for reproduction?

A

→ Differentiation into male or female
→ Sexual maturation

→ Production, storage and release sufficient supply of eggs and sperm
→ correct number of chromosomes in eggs and sperm
→ egg and sperm have to meet

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2
Q

What are cells that will become egg or sperm called?

A

→ Primordial germ cells

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3
Q

When are PGCs first identifiable?

A

→ in the yolk sac 3 weeks after conception

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4
Q

What happens to the PGCs?

A

→ the cells undergo many cycles of mitosis

→ They migrate to the genital ridge

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5
Q

What does the genital ridge become?

A

→ The gonad

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6
Q

What does further differentiation of the PGCs depend on?

A

→ The development of the gonad

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7
Q

What do germ cells become when in the ovary?

A

→ oogonia

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8
Q

What are oogonia?

A

→ Egg precursors

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9
Q

When oogonia enter meiosis what are they known as?

A

→ Primary oocyte

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10
Q

What phase do primary oocytes remain in and until when?

A

→ They remain in the first phase of meiosis until it ovulates or dies

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11
Q

Describe mitosis briefly

A

→ Spindle is formed
→ The chromatids are lined up one behind the other

→ They then separate to opposite poles of the cell
→ The cytoplasm divides and there are two identical cells

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12
Q

Describe meiosis

A

→ Duplication of the chromatids
→ They line up adjacent to each other

→ Chromosome 1 lines up with chromosome 1 from the other parent
→ allows crossing over and biological variation
→ homologous chromosomes separate into two haploid cells
→ separate again to form gametes
→oocytes are arrested in meiosis 1 until LH surge

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13
Q

where are primary oocytes packed?

A

→ Outer layer of the ovary : cortex

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14
Q

What do the cells around the oocyte become in the fetal ovary?

A

→ Condense around the oocyte and differentiate into granulosa cells

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15
Q

What do granulosa cells secrete?

A

→ Acellullar layer called the basal lamina

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16
Q

What does a primordial follicle consist of?

A

→ Oocyte with granulosa cells and a basal lamina

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17
Q

What do germ cells become in the ovary?

A

→ oogonia

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18
Q

What type of cell are oogonia and how do they multiply?

A

→ Diploid

→ Multiply by mitosis

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19
Q

What happens to the follicles at puberty and at menopause?

A

→ Follicles start growing at puberty

→ arrests at menopause

20
Q

What is folliculogenesis defined as?

A

→ Growth and development of follicles from the earliest resting stages as laid down in the fetus through to ovulation

21
Q

What happens as the follicles start to grow?

A

→ Granulosa cells multiply
→ Granulosa cells secrete basal lamina around it

→ oocyte secretes another protective acellular layer called the zona pellucida
→ Theca cells differentiate around the basal lamina

22
Q

What are theca cells and what is their purpose?

A

→ Steroid producing
→ they sustain the growth of the follicle and the oocyte
→condenses from interstitial cells in ovary

23
Q

What drives most of folliculogenesis?

A

→ FSH
→but early growth is independent of FSH i.e. driven by local factors
→Apparent in FSH-deficient patients or those with mutations of FSHr- we still see follicles in early stages

24
Q

What happens to follicles when FSH is suppressed eg on COCP?

A

→ The follicles will continue early growth but they die

25
Q

What happens in the second stage of follicle growth?

A

→ Increases rapidly in diameter
→ Granulosa cell divisions increase but gaps form in the cell layers

→ gaps form an antrum filled with follicular fluid- an exudate of plasma

26
Q

What are the two main phases of follicular growth?

A

→ Absence or presence of the antrum

27
Q

What are follicles with an antrum known as?

A

→ antral or secondary follicles

28
Q

What kind of cells do primordial follicles have and how do they look and grow?

A

→ flattened granulosa cells
→ grow in a slow and controlled manner

→ become cuboidal in shape

29
Q

Describe how primordial follicles physically change to become Graffian follicles

A

→ Granulosa cells
→ FSH causes granulosa cells to proliferate and the zona pellucida forms around the oocyte

→ theca cells are produced around the granulosa cells
→Theca cells condenses around and bring blood vessels with it exudate
→granulosa cell divisions increase and gaps form which are filled with follicular fluid
→these join and form the antrum
→ the egg is then within follicular fluid

30
Q

What are the cells directly surrounding the oocyte called?

A

→ Corona radiata

31
Q

Where are primordial cells arrested in?

A

→ Meiosis I

32
Q

What is follicle initiation?

A

→ When a cohort of follicles leave the resting pool and grow continuously
→starts from resting stage and NOT from antral stage

33
Q

What is follicle recruitment?

A

→ When the follicles are big enough to respond to changes FSH they start growing

34
Q

What do follicles need to continue growing?

A

→ FSH

35
Q

How long does the follicular phase last?

A

→ 14-15 days

36
Q

What is atresia?

A

→ When follicles die

37
Q

What steroids do the granulosa and theca cells produce?

A

→ Theca produces androgens which is stimulated by LH

→ androgens go to granulosa and get converted to estrogen which is stimulated by FSH

38
Q

What is the zona pellucida made of?

A

→composed ofthree glycoproteins: ZP1, ZP2, and ZP3.

→Receptors on the sperm plasma membrane attach to ZP3.

39
Q

What happens to granulosa cells fluid builds up?

A

→push granulosa cells outward and they are known as mural granulosa cells
→Cells around the egg become the cumulus complex

40
Q

Are pre-antral follicles visible on ultrasound?

A

Pre-antral follicles are NOT visible on u/s but are present all the time until menopause

41
Q

How many cycles does it take for a follicle to go from resting stage to ovulation?

A

3 cycles

42
Q

Why are theca cells vascularised?

A

→so follicle is open to influences of surrounding circulation and anything produced by follicle can enter circulation

43
Q

What is the two-cell-two-gonadotropin theory?

A

→luteinizing hormone stimulates thecal cells to produce androgens
→follicle-stimulating hormone stimulates granulosa cells to produce oestrogens from androgens.

44
Q

What is needed for the conversion of cholesterol to androstenedione?

A

LH and LHr found only on theca cells

45
Q

What is needed for the conversion of androstenedione to oestradiol?

A

→aromatase

→FSH found only on granulosa cells

46
Q

When are LHr found on granulosa cells?

A

→when there’s selection of dominant follicle which acquires LHr allowing it to make progesterone and oestrogen via delta4 pathway

Reproduction (12 decks)

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