Think about what would happen in each case…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Think about what would happen in each case.
- A drug stops the surge of LH on day .
- The corpus luteum is removed on day of a cycle without pregnancy.
- The ovum is fertilised and implants. Does the menstrual cycle go on?
Need a reminder? The key ideaShow
The average menstrual cycle lasts about days. The menstrual phase lasts to days. Ovulation takes place about days before the next menstruation, so in a cycle of days the day of ovulation is . The LH surge causes ovulation. The corpus luteum makes progesterone, which keeps the endometrium ready. If there is no fertilisation, the corpus luteum degenerates and menstruation begins.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) The Graafian follicle would not burst, so there would be no ovulation in that cycle.
Step 2. (b) The progesterone would fall, the endometrium would break down early, and menstruation would begin sooner.
Step 3. (c) No. In pregnancy all the events of the cycle stop, and there is no menstruation.
Answer: (a) no ovulation; (b) early menstruation; (c) the cycle stops.
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