Menstrual cycle Grade 12 Life Sciences Notes with Activities Questions and Answers

Menstrual cycle Grade 12 Life Sciences Notes with Activities Questions and Answers The menstrual cycle is a natural process that occurs in females of reproductive age. It involves a series of physiological changes in the female reproductive system, primarily in the ovaries and the uterus. Understanding the menstrual cycle is crucial for understanding reproduction and fertility.

Notes

Day 1–7

• Ovaries: New follicles develop and secrete oestrogen
• Uterus: Lining breaks down and is released (menstruation)

Day 8–13

Ovaries: Mature Graafian follicle develops:

• The Graafian follicle moves to edge of the ovary
• It secretes oestrogen

Uterus: Oestrogen stimulates the endometrium to become thicker and develop more blood vessels and glands

Day 14

Ovaries: Graafian follicle bursts to release an egg cell. The process is called ovulation

Day 15–22

• Ovaries: The Graafian follicle becomes a corpus luteum that secretes progesterone
• Uterus: Progesterone stimulates the endometrium to become even thicker and to develop more blood vessels and glands, ready to receive the embryo if an egg cell is fertilised

Day 23–28

Ovaries: If fertilisation does not take place:

• The corpus luteum shrinks and stops secreting progesterone

If fertilisation takes place:

• The corpus luteum remains active in the ovary and continues to secrete progesterone
• No more follicles develop in the ovaries
• No menstruation takes place

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Question and Answers Activities:

Find short and long questions for Grade 12 Life Sciences, which will help you to prepare for the exams, tests, practical tasks, and assignments.

Questions

1. Name the hormones A and B.
2. Give reasons for your answers in question 1.
3. What event occurs on day 14?
4. Name the other two hormones involved in this cycle.
5. Did fertilisation occur during the cycle shown in Figure 4.6?
6. Explain your answer in question 5.

Answers

Answers to activity 3

1. A – Oestrogen B – Progesterone
2. A: The Graafian follicle secretes oestrogen /Oestrogen reaches
   1. its maximum level before ovulation.
   2. B: The corpus luteum produces progesterone /Progesterone reaches its maximum level after ovulation.

3. Ovulation
4. LH and FSH
5. No
6. Progesterone levels decrease, towards the end of the cycle.

Phases of the Menstrual Cycle:

1. Menstrual Phase:
   • Duration: Typically lasts around 3 to 7 days.
   • Description: The uterus sheds its inner lining (endometrium), resulting in menstrual bleeding.
   • Hormonal Changes: Levels of estrogen and progesterone are low.
   • Activities:
     • Discuss the importance of menstrual hygiene.
     • Explore various menstrual products available and their pros and cons.
2. Follicular Phase:
   • Duration: Variable, usually around 7 to 10 days.
   • Description: Follicles in the ovaries develop and mature under the influence of follicle-stimulating hormone (FSH).
   • Hormonal Changes: FSH stimulates the growth of follicles, leading to increased estrogen production.
   • Activities:
     • Construct a diagram illustrating follicular development.
     • Research and present the role of FSH in the menstrual cycle.
3. Ovulation:
   • Duration: Typically occurs around day 14 of a 28-day cycle.
   • Description: A mature follicle releases an egg (ovum) into the fallopian tube.
   • Hormonal Changes: Surge in luteinizing hormone (LH) triggers ovulation.
   • Activities:
     • Simulate the process of ovulation using models or diagrams.
     • Discuss the signs and symptoms of ovulation.
4. Luteal Phase:
   • Duration: Approximately 14 days.
   • Description: The ruptured follicle transforms into a structure called the corpus luteum, which secretes progesterone.
   • Hormonal Changes: Progesterone levels rise, preparing the uterus for potential implantation of a fertilized egg.
   • Activities:
     • Research and present the functions of progesterone in the menstrual cycle.
     • Discuss the role of the corpus luteum in hormone production.

Regulation of the Menstrual Cycle:

• The menstrual cycle is regulated by a complex interplay of hormones produced by the hypothalamus, pituitary gland, ovaries, and uterus.
• Key hormones involved include FSH, LH, estrogen, and progesterone.
• Feedback mechanisms help maintain hormonal balance throughout the cycle.

Impact of the Menstrual Cycle:

• The menstrual cycle plays a crucial role in reproduction and fertility.
• It also affects various aspects of a woman’s health, including mood, energy levels, and physical symptoms.

Conclusion: Understanding the menstrual cycle is essential for both males and females, as it provides insight into reproductive biology and health. By studying the menstrual cycle, we gain a deeper appreciation for the complexities of the human body and the miracle of life.

Questions and Answers:

1. What is the primary purpose of the menstrual cycle?
   • Answer: The primary purpose of the menstrual cycle is to prepare the female reproductive system for potential pregnancy by regulating ovulation, maintaining the uterine lining, and ensuring hormonal balance.
2. How does the menstrual cycle differ from woman to woman?
   • Answer: The menstrual cycle can vary in duration and intensity from woman to woman. Factors such as age, hormonal balance, stress, and overall health can influence the length and regularity of the cycle.
3. Describe the role of hormones in the menstrual cycle.
   • Answer: Hormones such as FSH, LH, estrogen, and progesterone play critical roles in regulating the menstrual cycle. FSH stimulates follicle development, LH triggers ovulation, estrogen prepares the uterus for implantation, and progesterone maintains the uterine lining.
4. What are some common symptoms experienced during the menstrual cycle?
   • Answer: Common symptoms of the menstrual cycle include menstrual cramps, bloating, mood swings, fatigue, and breast tenderness. These symptoms can vary in severity and may be influenced by hormonal fluctuations.
5. How can individuals manage menstrual discomfort and maintain menstrual hygiene?
   • Answer: Individuals can manage menstrual discomfort through various methods such as pain relievers, heat therapy, exercise, and relaxation techniques. Maintaining menstrual hygiene involves using sanitary products, changing them regularly, and practicing good personal hygiene habits.

These notes provide a comprehensive overview of the menstrual cycle, including its phases, regulation, impact, and common questions and answers. Further exploration through activities and discussions can deepen students’ understanding of this important aspect of human biology.