Female Gamete Formation

Question 1

How many oocytes are present in the 20 week foetus?

Answer 1

5-7 million

Question 2

How many oocytes are present at birth?

Answer 2

1-2 million

Question 3

How many oocytes are present at puberty?

Answer 3

300,000

Question 4

Outline the formation of primary oocytes

Answer 4

Primordial germ cells migrate in to the ovary to form oogonia
The oogonia undergo multiple mitotic divisions to form the primary oocyte
It is surrounded by a single layer of granulosa cells (primary follicle)
Diploid cell

Question 5

At birth, oocytes are arrested at which stage of development?

Answer 5

Prophase 1

Question 6

What is the size of the resting follicle?

Answer 6

0.2mm

Question 7

What is the size of the follicle ready to ovulate?

Answer 7

20mm

Question 8

What changes to the oocyte happen at ovulation?

Answer 8

Completion of meiosis 1 to form the secondary oocyte and first polar body
Oocyte released from Graafian/tertiary follicle

Question 9

What changes happen to the oocyte at fertilisation?

Answer 9

Meiosis 2 is completed on entry of spermatozoa

Meiosis 2 gives rise to the ovum and second polar body

Question 10

Prior to fertilisation, the secondary oocyte is arrested at which stage of development?

Answer 10

Metaphase 2