Final answer:
The primary oocytes resume meiosis and complete the first meiotic division on a monthly basis.
Step-by-step explanation:
The primary oocytes resume meiosis where they left off and complete the first meiotic division on a monthly basis, for about the next 30 to 45 years. This occurs just before ovulation, when a surge of luteinizing hormone triggers the resumption of meiosis in the primary oocyte, leading to the formation of the secondary oocyte and a smaller cell called the first polar body.
The secondary oocyte eventually leaves the ovary during ovulation, while the first polar body may or may not complete meiosis and eventually disintegrates. Only one of the cells produced through oogenesis survives to become an egg.