Abstract: Primordial follicles have been formed before birth in mammals, and the reserve in follicle pool no longer increase after birth. With the activation of the primordial follicles, the follicles which were originally dormant gradually enter the growth stage, and gradually evolve from primary follicles and secondary follicles to antral follicles. Ovulation occurs in the dominant follicles with the stimulation of gonadotropins. Oocyte-derived and exogenous factors which regulate the maturation of oocytes, the proliferation and differentiation of the cells and granulosa cells through paracrine, autocrine, and endocrine ways. Besides, the communication between oocytes and granulosa cells through gaps junction allows synchronous development of all compartments of the follicle to maintain the follicle integrity. The thorough research on the mechanism of follicle activation and folliculogenesis will be beneficial to the solution of oocyte-related infertility in the field of reproductive medicine.

Key words: Ovarian follicle；, Oocytes；, Oogonia；, Signal transduction；, Meiosis