Q.Describe the process of oogenesis, including its hormonal control.

[!TLDR]

Oogonia become primary oocytes arrested in prophase I before birth; each post-pubertal cycle, one completes meiosis I (unequally) into a secondary oocyte arrested at metaphase II, released at ovulation, with meiosis II completed only on fertilisation; driven by GnRH, FSH and the LH surge. …

During foetal life, oogonia multiply mitotically and, by around the fifth month, all have entered meiosis I and enlarged into primary oocytes, each arresting in prophase I within a primordial follicle -- a state that persists from before birth until that particular follicle is recruited for growth after puberty. In each post-pubertal cycle, the primary oocyte of the maturing Graafian follicle resumes and completes meiosis I only shortly before ovulation, under the trigger of the mid-cycle LH surge, dividing unequally into a secondary oocyte (retaining nearly all the cytoplasm) and a small, non-functional first polar body. The secondary oocyte immediately enters meiosis II but again arrests, this time at metaphase II, and it is this arrested cell, still within its corona radiata and zona pellucida, that is released at ovulation. Meiosis II is completed -- again unequally, giving a mature ovum and a second polar body -- only if the secondary oocyte is fertilised; otherwise it degenerates. As with spermatogenesis, the proc …

Trace the two meiotic arrests explicitly -- prophase I (before birth, released just before ovulation) and metaphase II (at ovulation, released only on fertilisation) -- since this is what most disting …

Assuming meiosis I is completed before birth along with the arrest -- the primary oocyte arrests IN PROPHASE I, i.e. before completing the first division, and only actual …