Final answer:
A female reaches puberty with approximately 300,000 to 400,000 primordial follicles, declining from one to two million present at birth due to atresia. The follicles mature through a process called folliculogenesis, regulated by hormones, and about 400 to 500 will ovulate throughout the reproductive years.
Step-by-step explanation:
By the time a female reaches puberty, she has approximately 300,000 to 400,000 primordial follicles. These primordial follicles are present since birth when a female infant has one to two million oocytes within the ovarian follicles. This number declines due to a process called atresia, where follicles die off at various stages of development. During reproductive years, following puberty, only about 400 to 500 of these follicles will go through the full maturation process leading to ovulation, while the others will undergo atresia. The transition of a primordial follicle to a primary follicle and then to further stages is a part of folliculogenesis, a complex development process tightly regulated by hormones such as GnRH, LH, and FSH. Each month, a cohort of these follicles is recruited, with typically only one reaching full maturity and being released as an oocyte during ovulation, which occurs approximately every 28 days.