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ICSE Question Bank
2016Q5(b)(iii)The Reproductive System
ReasoningHard1 mark
5(b)

Give scientific reasons for the following statements:

When an ovum gets fertilized, menstrual cycle stops temporarily in a woman.

Topic: Menstruation stops after fertilisation

Previous-year question practice database

Answer

Exam answer

Because the CORPUS LUTEUM PERSISTS and continues to secrete PROGESTERONE. Progesterone maintains the thickened, vascularised ENDOMETRIUM in a state suitable for the embryo, which implants in it. Since the lining is not broken down, menstruation does not occur.

Explanation

The answer must name the CORPUS LUTEUM and PROGESTERONE — those are the two ideas being tested.

THE CONTRAST makes it clear, and giving both halves is what earns the mark: if the ovum IS fertilised — the corpus luteum PERSISTS, progesterone stays HIGH, the lining is MAINTAINED, no menstruation if it is NOT fertilised — the corpus luteum DEGENERATES, progesterone FALLS, the lining can no longer be maintained and is SHED as menstruation

So the fate of one small structure decides whether a pregnancy continues or a period begins.

Later in pregnancy the PLACENTA takes over the secretion of progesterone.

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