Final answer:
After puberty, some primordial follicles respond to a recruitment signal and develop into primary follicles. Granulosa cells become active, the follicles increase in size and add new layers of tissue. However, most follicles do not reach ovulation and undergo atresia.
Step-by-step explanation:
After puberty, a few primordial follicles respond to a recruitment signal each day and join a pool of immature growing follicles called primary follicles. The granulosa cells in the primary follicles become active and transition from a flat shape to a rounded shape as they divide and increase in size. The follicles then increase in diameter, adding a new outer layer of connective tissue, blood vessels, and theca cells, which work with granulosa cells to produce estrogens.