Final answer:
The menstrual cycle consists of a preovulatory phase, which prepares the uterus for possible pregnancy, and a postovulatory phase, when the uterus is ready to receive a fertilized egg. The preovulatory phase includes menstruation and the proliferative phase, while the postovulatory phase entails the secretory phase dominated by the luteal phase. If no LH surge occurs, ovulation and the subsequent luteal phase events are inhibited.
Step-by-step explanation:
Overview of the Menstrual Cycle
During the menstrual cycle, the uterus undergoes various changes in the preovulatory and postovulatory phases. The preovulatory phase, or follicular phase, starts on the first day of menstruation and continues until ovulation. This phase is characterized by the shedding of the endometrial tissue, which generally occurs from days 1 to 5. Following this, the proliferative phase begins, during which the endometrium rebuilds in anticipation of a possible pregnancy, peaking at ovulation around day 14.
After ovulation, the postovulatory phase, or luteal phase, commences, which runs approximately from day 15 to day 28. During this phase, the ruptured follicle transforms into the corpus luteum, which releases progesterone and estrogen. These hormones facilitate the regeneration of the uterine lining, preparing the uterus to accept a potential fertilized egg. If fertilization does not occur, the corpus luteum degenerates, resulting in a decrease in hormone levels and the onset of menstruation.
If an LH surge did not occur, ovulation would not take place, and the follicle would not transform into a corpus luteum, disrupting the cycle.