Hi Mar,

Once the oogonium undergoes mitosis, it becomes a primary oocyte, and then it starts meiosis I and stops at prophase I. Is the hormone FSH responsible for the "reactivation" of meiosis I to form the secondary oocyte?

For this question, I am unsure, and I've consulted a couple of human reproductive textbooks on this - they all seem to treat the processes stimulated by FSH (estrogen production, development of ovarian follicles) seperately from the restarting meiosis I.

This leads me to suspect that the mechanism by which FSH and this meiotic restarting are related is unclear (if they are related at all).

However, it is mentioned that FSH promotes growth of multiple follicles, and usually only one develops into a mature follicel.

I would guess it's more in a loosely related way in that FSH provides the oocyte with the opportunity to restart, and it's kind of up to the cell stochastically on its own, or there is some intermediate messenger - after all, you can have fraternal twins, which shows you can stochastically have 2 eggs form from meiosis at the same time.


And also, once LH stimulates the release of the secondary oocyte from the ovary, does meiosis II restart (after it stoped at metaphase II) once the sperm has entered it? Or does it complete meiosis II before the sperm fertilizes it?

Meiosis II is only resumed after metaphase II only when fertilized by a sperm.

Great questions!

Katt