Folliculogenesis

Question 1

How do Primordial Germ Cells become a Primary Oocyte?

Where are the Primary Oocytes stored?

Answer 1

• Germ cells enter Ovary to become Oogonia - egg precursors that divide by mitosis

• Once mitosis stops, they enter into Meiosis to produce Primary Oocytes (Diploid)
o NO MORE DIVISION OCCURS ONCE IT ENTERS THE 1ST STAGE OF MEIOSIS

• Primary Oocytes remain in the 1st phase of Meiosis until Ovulation or death (40-52yrs)

• Stored in Ovary cortex (outer layer)

Question 2

What’s the Primordial Follicle?

What forms around the Oocyte?

What happens to the Granulosa layer as the follicle grows?

What is the outermost layer of the follicle? What is important about this layer?

Answer 2

• Oocyte surrounded by protective layers and cells
• Surrounding cells condense around Oocyte and differentiate into GRANULOSA cells, which secrete an acellular (no cells) layer, called the Basal Lamina
• Granulosa cells multiply and the Oocyte secretes another acellular layer, called the Zona Pellucida
• Theca cell layer - VASCULARISED for the hormones to reach it

Question 3

Follicle growth:
What occurs?

What do these gaps get filled with? What is the follicle now called?

What is it mainly driven by? What drives early growth?

What occurs in Follicle Initiation?

What occurs in Follicle Recruitment?

Answer 3

• Rapid increase in diameter, and Granulosa cells divide even more to form gaps in its layer
• Filled with follicular fluid to form an Antrum = Antral/Secondary Follicles
• FSH, but early growth is independent of FSH (driven by local factors)
• Group of early follicles leave the resting pool and grow continuously
• They won’t continue growing if they’re not big enough to respond to changes in FSH during the Menstrual cycle

Question 4

Where are the LH receptors found? What does it produce?

Where are the FSH receptors found? What does it produce?

Answer 4

• LH receptors on Theca cells produce Progesterone and Androgens
• FSH receptors on Granulosa cells produce Oestrogen