Question 11 of 15intermediate💡 UnderstandLong Answer5 marks

What is menstrual cycle? Which hormones regulate menstrual cycle?

Correct Answer

Menstrual cycle is the reproductive cycle in female primates (monkeys, apes, humans). It begins at puberty with menarche and ends at menopause around age 50. The cycle averages 28/29 days, from one menstruation to the next, and involves ovulation (release of one ovum) in the middle.

The cycle consists of the following phases: (i) Menstrual phase (3-5 days): breakdown of endometrium and blood vessels leads to menstrual flow if fertilisation hasn't occurred. (ii) Follicular phase: primary follicles mature into Graafian follicle; endometrium regenerates. (iii) Ovulatory phase: LH surge around day 14 triggers ovulation. (iv) Luteal phase: corpus luteum forms and secretes progesterone to maintain endometrium; if no fertilisation, corpus luteum degenerates, leading to menstruation.

The hormones regulating the cycle are gonadotropins (LH and FSH), estrogens, and progesterone. FSH and LH increase during follicular phase, stimulating follicular development and estrogen secretion. The LH surge induces ovulation. Progesterone from corpus luteum maintains the endometrium. During pregnancy, the cycle stops.

Exercise: EXERCISES | Q: 17 | (Page 40)
For More Understanding

Explanation

The answer defines the menstrual cycle, its duration, and phases based on the textbook content. It then lists the key hormones (LH, FSH, estrogen, progesterone) and briefly describes their roles, as extracted from the provided context (e.g., LH surge, follicular development, progesterone maintenance). All facts are taken directly from the given text without external addition.

Solution Steps

  1. Step 1: Define menstrual cycle using textbook statements: reproductive cycle in female primates, starts at menarche, ends at menopause, repeats every 28/29 days, involves ovulation.

  2. Step 2: Describe the four phases (menstrual, follicular, ovulatory, luteal) with key events from the context.

  3. Step 3: Identify the hormones that regulate the cycle: gonadotropins (LH, FSH), estrogens, progesterone, and explain their functions as mentioned in the text.

  4. Step 4: Conclude with the effect of pregnancy on the cycle (stops menstruation).

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