Question about folliculogenesis

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Danny L

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So this NS passage mentions that folliculogenesis lasts for 5 menstrual cycles. Is that just saying that the duration is 5 menstrual cycles, or is that saying 5 menstrual cycles take place before folliculogenesis happens.

I thought the process was: menstruation->folliculogenesis and ovulation->repeat

Thanks

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I believe it is saying that the duration of folliculogenesis for an individual follicle is 5 cycles. Follicles go through many stages so the time between the two they are choosing as the start and end point is 5 cycles.

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Hi Danny L,

It sounds like you're asking about Passage 3 in the Bio/Biochem section of our Full Length #2, which is indeed a very challenging passage.

So, the short answer to your question is that if a passage tells you that folliculogenesis takes 5 menstrual cycles in mice, just run with it :). The duration of folliculogenesis in mice certainly is not within the bounds of what the MCAT expects you to know off the top of your head, so this is a place where you want to work with what they give you in the passage.

However, your question about the content is excellent, and deserves a fuller answer. You're absolutely right that when we think about the timing of the menstrual cycle, the maturation of a follicle is a step that happens after menstruation. Stepping back, when studying the menstrual cycle, it's a good idea to be careful to distinguish between the ovarian and the uterine cycles -- folliculogenesis happens in the ovaries, whereas menstruation (the shedding of the uterine lining) takes place in the uterus -- because doing so will help clarify the underlying logic of the process, but you're basically right. The issue here is that the follicular phase of the menstrual cycle involves the final maturation of a follicle, not the entire process of folliculogenesis. The whole process of folliculogenesis takes several menstrual cycles in humans. The exact details go beyond what you're likely to be required to know for the MCAT, but Wikipedia gives a figure of 375 days (=13 menstrual cycles), this online textbook on obstetrics and gynecology gives a figure of at least 300 days, and this review article suggests that the antral phase is on the order of 160 days. So the basic idea is that at any given time in the ovary, you have follicles in all states of maturation, and that the follicular phase of the menstrual cycle coincides with the final maturation of a follicle, not the whole process starting from scratch.

Therefore, in the context of this passage, what the authors are saying is that mice are a good model organism to study folliculogenesis in because it takes less time (5 cycles) than in humans.

Hope this helps, and best of luck!
 
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