Final answer:
A tertiary follicle differs from a primary follicle by having a fully formed fluid-filled cavity named the antrum, which is essential for its development into a mature follicle ready for ovulation.
Step-by-step explanation:
A tertiary follicle is different from a primary follicle in that it has a cavity known as the antrum. This fluid-filled chamber is a hallmark of a mature tertiary follicle. Follicular development progresses from a primordial follicle to the primary follicle stage, where granulosa cells proliferate and form multiple layers. As the secondary follicle develops, the primary oocyte secretes the zona pellucida. The granulosa cells start to accumulate follicular fluid, which gradually coalesces into the antrum. As the tertiary follicle continues to grow, it is prepared for the potential ovulation of its secondary oocyte, which is surrounded by granulosa cells.During this process, the primary oocyte is shielded by the zona pellucida and the corona radiata, a layer of granulosa cells. After the release of the oocyte, if fertilization does not occur, the remaining structure in the ovary develops into the corpus luteum, which eventually degenerates if pregnancy does not ensue.