Question about Female Reproductive Oogenesis

[rom73085]

So I'm trying to grasp Oogenesis and ovulation and I'm using TPR hyperlearning bio book to figure it out.

I understand that Oogonia are produced in the female embryo prior to birth. The oogonia undergo mitosis and form primary oocytes which then is halted a few months after the female infant is born.

Upon puberty, the number of oocytes begin decreasing.

What I'm confused about is this statement:

"The primary oocytes formed in a female embryo are frozen in prophase I for decades, until they re-enter the meiotic cycle."

I don't quite understand because then it goes onto to state that during each menstrual cycle, the primary oocytes once again undergo meiosis, thus becoming a secondary oocyte which goes from the ovary into the fallopian tube and is said to be "ovulated."

This doesn't make sense. Females begin their menstrual cycle as young females. Why does it state that the primary oocytes are frozen in prophase I for decades?

For those of you that own the book, its pg. 332. Thanks!

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[GRod18]

well, the primary oocyte is frozen at meiosis I for decades meaning that throughout the life of a woman, (before menopause) she is able to ovulate these eggs once a month. During ovluation it turns into 2ndary oocyte and polar body. If 2ndary oocyte is fertilized by sperm it will finish meiosis 2 and become the mature ovum. I believe it is arrested in meta phase of meiosis 2 before fertilization. I think menopause happens at different ages for different women, but women can ovulate well into their 40s 50s I believe, hence they are saying that many are arrested for decades meaning that the unovulated eggs are all still arrested as primary oocyte.

 

[enoknight]

Most women continue to ovulate until menopause, which is a few decades (~4 decades, I guess).

Most of the oocytes are in stuck prophase I within 1-2 months of development, waiting for the estrogen surge to trigger LH and FSH surges that arrive during puberty. Of course, not all the oocytes are released at the same time so most of them remain in the ovaries until they are released or until they start to degrade since reproduction is no longer optimal.

 

[rom73085]

Yep - makes sense now. I talked to one of my friends who's a nurse and the way she put it made more sense. Basically, those primary oocytes, only ONE is released for ovulation that undergoes the secondary meiosis. Essentially, it is right to say, the primary oocyte is frozen for decades at meiosis I, but the wording is just awkward.

\thread. Thanks guys!