MENSTRUAL CYCLE

 

Have you ever wondered what the connection is between your body's menstrual cycle and the cycle of the moon?  Many years before electricity, women's bodies were influenced by the amount of moonlight we saw. Just as sunlight and moonlight affect plants and animals, our hormones are triggered by levels of moonlight. Today, with artificial light everywhere, night and day, our cycles can no longer correspond with the moon.

The menstrual cycle is regulated by the Luteinizing hormone and the follicle-stimulating hormone, which are produced by the pituitary gland, promote ovulation and stimulate the ovaries to produce estrogen and progesterone. Menstruation is the shedding of the lining of the uterus called the Endometrium, which is accompanied by bleeding. Menstruation occurs if the Ovum is not fertilized by sperm and the Corpus Luteum which is a ruptured follicle, disintegrates. The endometrium begins to slough off due to lack of blood since progesterone and estrogen levels drop in the last week of your menstrual cycle. The menstrual cycle begins with the first day of bleeding, which is counted as day 1. The cycle ends just before the next menstrual period. Menstrual cycles normally range from about 25 to 36 days. Menstrual bleeding lasts 3 to 7 days, averaging 5 days. Blood loss during a cycle usually ranges from ½ to 2½ ounces.

There are three phases the menstrual cycle goes through. First the cycle begins with menstrual bleeding, which marks the first day of the follicular phase. The follicle-stimulating hormone (FSH) level increase, stimulating the development of follicles. As the FSH level decreases, only one dominant follicle continues to develop and begins to produce estrogen.  The second phase is the Ovulatory phase which begins when the Luteinizing hormone (LH) increases and stimulates the dominant follicle to release an egg. This phase usually lasts between 16 and 32 hours and ends when the egg is released. Then 12 to 24 hours after the egg is released, the LH can be detected by measuring the level of this hormone in urine. This measurement will be performed with an Ovulation Prediction Kit (OPK). Lastly after ovulation, the Luteal phase begins which only lasts about 14 days. The ruptured follicle closes after releasing the egg and forms the corpus luteum which in turn produces progesterone. The progesterone causes the endometrium to thicken in order to nourish a potential fetus. If the egg is not fertilized, the corpus luteum degenerates after 14 days, and a new menstrual cycle begins.

References:

Hogan, M.A. (2007). Comprehensive Review For NCLEX-RN. Upper Saddle River, NJ. Pearson Prentice Hall

Rosenblatt, MD, P. (2007). The Merck Manuals Online Medical Library. Retrieved from http://www.merck.com/mmhe/sec22/ch241/ch241e.html

(2010). Menstrual Cycles: What Really Happens in 28 Days? Retrieved from http://www.fwhc.org/health/moon.htm

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