Menstrual Cycle

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Menstrual Cycle
2013-01-28 11:36:35
Bio 220

Chapter 46
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  1. What is an important factor in this cycle?
  2. What happens at the beginning of the cycle? 
    After that occurs?
    • a.       Beginning of cycle: menses
    • b.      After menses is complete, estrogen levels are building up
  3. What does estrogen cause?
    •                                                                           i.      causes proliferation of the endometrium (glandular epithelium) when menses is finished
    • 1.      causing increase in height of the lining
  4. What occurs at mid-cycle?
    a.       levels start decreasing because its done it’s job because it has started the proliferation of the endometrium, but it can’t make the endometrium reach its height
  5. What is progesterone's job?
    • 1.      Completes proliferation of endometrium to its maximum height and maintains this height of the endometrium
    • a.       Keeps it up there
  6. If not pregnant:
    •                                                                           i.      Toward end of cycle, LH goes away, which was maintaining the corpus luteum, keeping it producing progesterone
    • 1.      Without LH, corpus luteum dies and progesterone levels drop, causing the progesterone levels to cause menses of the endometrium
  7. If pregnant:
    •                                                                           i.      LH still disappears because high estrogen levels cause it to turn it off; but it has no effect because HCG maintains the corpus luteum and keeps it secreting progesterone during the first trimester
    • 1.      After the first trimester, HCG disappear but progesterone levels don’t decrease because the placenta is producing progesterone