Main Answer:
If fertilization doesn't occur, the corpus luteum degenerates.
Step-by-step explanation:
After ovulation, the ruptured follicle transforms into the corpus luteum, a temporary endocrine structure that plays a crucial role in preparing the uterine lining for a potential embryo. If fertilization does not take place, the corpus luteum's life span is limited. Without the hCG (human chorionic gonadotropin) signal from a developing embryo, the corpus luteum ceases to receive the necessary support to maintain its structure and function.
The degeneration of the corpus luteum involves a decrease in hormone production, primarily progesterone. Progesterone is essential for maintaining the uterine lining, creating a favorable environment for implantation. As the corpus luteum regresses, progesterone levels decline, triggering the shedding of the uterine lining in the form of menstruation.