Let’s Talk About Menstruation

    What do you know about your period?  I mean, we’ve all been taught that it happens because of ovulation.  But beyond that, what do you really know about menstruation?

    I faced this question in my physiology class last term.  To my chagrin, I learned I actually knew very little about this monthly visit.  Previous “sex ed” courses never fully explored the hormonal and physical changes that occur.  So, here goes a brief explanation about the fascinatingly complex gift Mother Nature bestows upon us:

  1. A follicle is a group of cells in which the egg is stored.  10-25 follicles are initially chosen to undergo development.

  2. Estrogen levels rise, and the endometrial layer of the uterus thickens.

  3. One dominant follicle, from the previous 10-25, is chosen to be ovulated.  The other follicles and eggs die.

  4. The level of the hormone LH rises drastically, in what is known as the LH surge.  The LH surge causes ovulation to occur, around day 14 of the cycle.

  5. Progesterone levels rise during ovulation.  The glands of the endometrium become filled with glycogen (a storage form of sugar).  The number of blood vessels in the uterus increases.  These changes prepare the uterus for potential implantation of a fertilized egg.

  6. If the egg isn’t fertilized, progesterone and estrogen levels decrease around day 25 of the cycle.

  7. Blood vessels in the uterus constrict, lowering blood flow to the uterus.  Endometrial cells degenerate, which causes bleeding to occur as the endometrium is sloughed off.

  8. The first day of bleeding is counted as the first day of the menstrual cycle.

     Sorry, I know that was a lot of science terminology I just threw at you.  To make up for it, I’ll highlight some important, but less jargon-filled, implications of this cycle.

    First, hormonal birth control does not prolong a woman’s reproductive lifespan.  Although The Pill prevents the ovulation of an egg, it does not save this egg from dying.  With hormonal contraceptives, none of the follicles can mature enough to reach the “dominant” stage.  Therefore, all 10-25 follicles (and the eggs they hold) die.

    Second, counting the number of days in a cycle is not an entirely reliable method of birth control.  Bleeding starts on day 1, and ovulation usually occurs around day 14.  However, cycles vary.  The LH surge ovulation can occur anywhere from day 3 to 27.

    Overall, it’s fascinating to consider the changes the female body naturally goes through.  Our body maintains the intricate fluctuations of estrogen, progesterone, and LH each month.  It automatically prepares our uterus for possible fertilization, and quickly adapts when fertilization doesn’t occur.  Periods are complex, sometimes painful, and well worth demystifying.


Michelle Torby
University of Michigan
English Language and Literature

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