What happens to all the female germ cells?


Here’s a little semi-interactive drawing I put together that shows what happens to the germ cells over the course of a female’s life, from fetal life until menopause.

Scroll down to see how the number (and stage of development) of germ cells changes as a woman ages.

Pay particular attention to what happens during the ages in red ovals:
1. Hover over a red oval and see if you can answer the question that pops up.
2. Click the red oval to see the answer.

When you’re done, scroll way down to the bottom to check out the takeaway points.


    Here are the main takeaway points.

    1. By the time baby is born, all her oogonia are gone!
    They’ve all transformed into primary oocytes (which are stuck in prophase I).

    2. Almost all of these primary oocytes will remain halted at prophase forever.
    Only a few (around 50) are selected for maturation at the beginning of each menstrual cycle.

    3. Most of the 50 primary oocytes selected each month end up dying – only one makes it to ovulation.
    All 50 primary oocytes in the chosen group start the process of follicular maturation – but along the way, most of them die. Only one actually makes it to the Graafian follicle stage. When LH surges, that lonely primary oocyte (in its Graafian follicle) completes meiosis I, and becomes a secondary oocyte, which is then ovulated.

    4. Every year, starting at birth, the population of primary oocytes dwindles.
    At birth, there are around 2 million primary oocytes – but by puberty, there are only around 400,000 left. At that point, a measly 50 primary oocytes are given a shot at maturation each month. The rest just sit there, wondering if they’ll be chosen next time. Meanwhile, they keep dying off – and by menopause, there are no primary oocytes left.