What structure is formed after ovulation that plays a crucial role in hormone production during the menstrual cycle?

The structure formed after ovulation that plays a crucial role in hormone production during the menstrual cycle is the corpus luteum. After the release of an egg from the ovary—a process known as ovulation—the remnants of the follicle that housed the egg undergo transformation to form the corpus luteum. This temporary endocrine structure is vital for regulating the menstrual cycle and early stages of pregnancy.

The corpus luteum secretes hormones such as progesterone and estrogen, which are essential for preparing the uterine lining for potential implantation of a fertilized egg. If pregnancy does not occur, the corpus luteum eventually degenerates, leading to a decrease in hormone production and the onset of menstruation. However, if fertilization does happen, the corpus luteum persists and continues to secrete these hormones until the placenta can take over hormone production.

Other structures listed, such as the Graafian follicle and the ovarian follicle, are involved in the earlier stages of the reproductive cycle, specifically during the egg maturation process, and do not produce hormones after ovulation. The amniotic sac, while important during pregnancy, is not formed until after fertilization and does not play a role in hormone production related to the menstrual cycle.