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MCAT Biology

Discussion in 'MCAT Discussions' started by Jonkst, Aug 14, 2002.

  1. Jonkst

    Jonkst Senior Member

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    Quick question about a Biology topic:
    Can anyone explain the menstrual cycle stuff. I have yet to find a source that explains it well.

    I have a feeling I'm going to get some interesting responses to this one...
     
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  3. rCubed

    rCubed taiko master

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    hmmm...let me take a stab at it

    first of all, remember...estrogen will stimulate gonadotropin releasing hormone (GnRH) which will stimulate LH and FSH

    however, estrogen and progesterone together inhibit GnRH which in turn inhibits LH and FSH


    ok, step by step:

    I. Follicular phase: FSH and LH are both being secreted, this is just after the woman has completed menstration. FSH and LH at this point develop ovarian follicles which in turn secrete estrogen, which will stimulate GnRH, which will stimulate even more LH and FSH

    II Ovulation: Now we have alot more LH which stimulate ovulation, or release of the egg from the ovary....

    III Luteal phase: now there's still all that LH and it acts on the follicle to develop it into the corpus luteum. the corpus luteum secretes estrogen and progesterone. both of these together will not only cause the endometrium to develop and vascularize, they'll make the LH and FSH secretions stop

    IV Menstration: this occurs only if there is no fertalization. the corpus luteum degenerates, thus no more progesterone and estrogen..so no more thick uterine lining, so menstration occurs. and since the corpus luteum just degenerated, and theres no more estrogen and progesterone together, LH and FSH can be secreted again



    hope that sort of helps, its a really short overview
     
  4. Jonkst

    Jonkst Senior Member

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    Thanks rCubed. I appreciate it. Simple is fine; all I need for the MCAT anyway. "thus no more progesterone and estrogen" was all I needed to clear it up.

    Good luck to ya'
     
  5. limit

    limit Molesting my inner-child

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    Why do you females have to be so complex?? :p
     
  6. rCubed

    rCubed taiko master

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    so the curve is in our favor:D
     

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