Figure 3. Stages of ovarian follicular development.

Folliculogenesis requires a coordinated progression of growth of ovarian follicles. The process begins with the germ cells which are recruited to a pool of primordial follicles. The primordial follicles progress to primary and then secondary follicles. At the secondary follicle stage, theca cells are present. The early antral follicle stage is defined by the presence of antrum. The peri-ovulatory follicle stage is also known as the dominant follicle and is ready for ovulation. this stage, cumulus and mural granulosa cells are present. Once the oocyte is ovulated, the remaining granulosa cells become the corpus luteum. This cycle of folliculogenesis occurs for every single oocyte ovulated.