Step 1: Overview of the Menstrual Cycle.
The menstrual cycle is a monthly process in females that prepares the body for a potential pregnancy. It typically lasts for 28 days, though it can range from 21 to 35 days. The cycle is divided into four main phases:
1. Menstrual Phase: This is when the uterine lining sheds if fertilization has not occurred, resulting in menstruation (period).
2. Follicular Phase: Follicle-stimulating hormone (FSH) stimulates the growth of ovarian follicles, and the endometrium (lining of the uterus) thickens in preparation for implantation.
3. Ovulation: A mature egg is released from the dominant follicle in the ovary. This is triggered by a surge in luteinizing hormone (LH).
4. Luteal Phase: After ovulation, the ruptured follicle forms the corpus luteum, which secretes progesterone to maintain the uterine lining. If no fertilization occurs, the corpus luteum degenerates, leading to a decrease in progesterone and the beginning of menstruation.
Step 2: Diagram of Menstrual Cycle. Step 3: Conclusion.
The menstrual cycle is regulated by hormonal changes and involves the maturation of an egg, the shedding of the uterine lining, and preparation for potential pregnancy.
Final Answer:
\[
\boxed{\text{The menstrual cycle involves four phases: Menstrual, Follicular, Ovulation, and Luteal.}}
\]
