Use the graph of the lesson, with a cycle of 28 days…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Use the graph of the lesson, with a cycle of days.
- Which hormone has a sharp peak at about day and causes ovulation?
- Which hormone rises most after ovulation and keeps the endometrium ready?
- Which structure makes this hormone?
- Which hormone is made by the growing follicles in the follicular phase?
- What causes the menstruation at the end of the cycle?
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) LH, the LH surge.
Step 2. (b) Progesterone. It peaks in the luteal phase.
Step 3. (c) The corpus luteum.
Step 4. (d) Oestrogen.
Step 5. (e) The corpus luteum degenerates, the progesterone falls and the endometrium breaks down.
Answer: (a) LH; (b) progesterone; (c) corpus luteum; (d) oestrogen; (e) the fall of progesterone.
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