What is menstrual cycle? Which hormones regulate menstrual cycle?
Explanation If an ovum remains unfertilized in the ovary of a female, the lining of the uterus is shed. This process is called menstruation. The cycle of events starting from one menstruation till the next one is called the menstrual cycle. The first day of bleeding is called the first day of the menstrual cycle. A single menstrual cycle lasts for a period of 28-30 days. The menstrual phase lasts for about 1-4 days during which the menstruation occurs. The follicular phase ranges from the 5th to the 13th day in which the follicle attains maturity and the endometrium develops. During the ovulation phase, which occurs on the 14th day, the ovary releases an ovum or egg. The luteal phase lasts from the 15th day to the 28th day during which the follicle changes into the corpus luteum and the endometrium develops to prepare for the ovum. Final Answer During the follicular phase, secretion of gonadotropins like luteinizing hormone (LH) and follicular stimulating hormone (FSH) increases. This stimulates the development of the Graafian follicle. On the 14th day, the level of both LH and FSH is at its peak. The LH surge induces the rupture of the Graafian follicle. During the luteal phase, the Graafian follicle behaves as the corpus luteum and secretes high amounts of progesterone to maintain the endometrial wall. In the absence of fertilization, the corpus luteum undergoes degeneration and the endometrium begins to disintegrate. This initiates the start of a new menstrual cycle.
