Final answer:
The Graafian follicle turns into the corpus luteum following ovulation. It secretes progesterone, which supports potential pregnancy, and if fertilization doesn't occur, it degenerates, triggering menstruation.
Step-by-step explanation:
After ovulation, the Graafian follicle, which previously housed the ovulated egg, becomes the corpus luteum. This is a process known as luteinization, stimulated by a surge in the luteinizing hormone (LH).
The corpus luteum is a temporary endocrine structure that secretes large amounts of the hormone progesterone, which is essential for establishing and maintaining a potential pregnancy. Progesterone also exerts negative feedback on the hypothalamus and pituitary, preventing the maturation of new dominant follicles during this time.
Furthermore, as part of the luteal phase of the menstrual cycle, if the secondary oocyte released during ovulation is not fertilized, the corpus luteum will eventually degenerate, leading to a decrease in progesterone levels and the beginning of menstruation.