The development of a tertiary follicle begins with the formation of a primary follicle from the primordial follicle. The primary follicle then transitions into a secondary follicle, where multiple layers of granulosa cells form around the oocyte. As the follicle continues to mature, it becomes a tertiary follicle, marked by the appearance of the antrum. This antrum is filled with follicular fluid, which provides a nutrient-rich environment for the oocyte.
