Folliculogenesis

Question 1

Where do germ cells enter into?

Answer 1

Enter the gonads

Question 2

What are cells called that will become eggs or sperm?

Answer 2

These are called primordial germ cells

Question 3

When are primordial germ cells first identifiable?

Answer 3

First identifiable in the yolk sac of the developing foetus at 3 weeks after conception

Question 4

What do primordial germ cells undergo and migrate to where?

Answer 4

PGC undergo many cycles of mitosis and migrate to the genital ridge in the foetus

Question 5

What becomes the gonad?

Answer 5

The genital ridge becomes the gonad

Question 6

What does further differentiation of the PGC depend on?

Answer 6

Depends on the development of the gonad

Question 7

What do primordial germ cells become when they enter the ovary and how?

Answer 7

If PGCs enter the ovary, they become oocytes.

1. Germ cells become oogonia when in the ovary
2. Oogonia are egg-precursors, diploid and multiply by mitosis
3. Once mitosis stops and they enter into meiosis, they’re known as primary oocytes

Question 8

How does duplication of chromatids occur?

Answer 8

• Chromosomes replicate during s-phase of the cell cycle
• Chromatids remain attached at the centromere
• Each copy known as a chromatid

Question 9

Mitosis and Meiosis steps

Answer 9

LOOK OVER IN DETAIL IN OWN TIME

Question 10

Where are primary oocytes packed into?

Answer 10

Primary oocytes are packed into the outer layer of the ovary:the cortex

Question 11

How do we go from primary oocyte to primordial follicles?

Answer 11

-Primary oocytes are in the vulnerable 1st meiotic phase for many years
-Therefore each one becomes surrounded by
protective layers and protective cells
-In the foetal ovary, the surrounding cells condensate around the oocyte and differentiate into the granulosa cells
-The granulosa cells then secrete an acellular layer
called the basal lamina
-This whole structure is called the primordial follicle

Question 12

What is folliculogenesis?

Answer 12

It is the growth of the follicle

Question 13

What is folliculogenesis defined as?

Answer 13

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

Question 14

Comment on the growth of follicles after puberty?

Answer 14

Most of the follicles in the ovary are not growing after puberty, after puberty only a few grow

Question 15

What happens a s the follicles start to grow?

Answer 15

As the follicles start to grow, the granulosa cells multiply and the oocyte secretes another protective acellular layer called the zona pellucida which stays attached after ovulation

Question 16

What else grows once growth of the follicles start?

Answer 16

Once growth of the follicles has started, a second layer of cells then differentiate around the basal lamina:the theca

Question 17

What drives most of folliculogenesis and early follicle growth ?

Answer 17

FSH drives most of folliculogenesis but early growth is independent of FSH and is driven by local factors

Question 18

What happens when FSH is suppressed in follicle growth?

Answer 18

When FSH is suppressed, the follicles will still continue early growth but then die

Question 19

What happens as follicles start to grow and what do they consist of?

Answer 19

As follicles start to grow, it increases rapidly in diameter and granulosa cell division increase, but gaps begin to form in the granulosa cell layers
-These gaps consist of fluid filled space which form an antrum and are filled with follicular fluid

Question 20

What are follicles known as before an antrum and what do they have?

Answer 20

Before the antrum, they’re known as pre antral follicles and just have a layer of granulosa cells with theca

Question 21

What are follicles known as after the formation of the antrum?

Answer 21

After the formation of an antrum, they’re known as secondary follicles

Question 22

What happens to the oocyte as the follicle grows?

Answer 22

As the follicle grow, the oocyte is displaced to one side

Question 23

What is follicle initiation?

Answer 23

It is where a cohort of early follicles leave the resting pool and grow continuously

Question 24

What is follicle recruitment?

Answer 24

When follicles see FSH at the the right time and are recruited by the menstrual cycle for continuous growth

Question 25

What is the follicular phase of the menstrual cycle?

Answer 25

It is the phase just after the formation of the antryma and just before ovulation

Question 26

What do ovarian follicles produce and what is this called

Answer 26

Produce steroids

and is called the 2 cell 2 gonadotropin theory

Question 27

What is the 2 cell 2 gonadotropin theory?

Answer 27

-LH binds to LH receptor on theca cell and produces the androgen
-These androgens go into circulation but also cross the granulosa membrane and are converted into oestrogen
-Oestrogen will drive granulosa cells in the follicle and
go out in circulation
-FSH binds to FSH receptor and catalyses the conversion of androgens in to oestrogens