How Your Menstrual Life Cycles Continue to Function
If you don't become pregnant (either by choice or for other reasons), your corpus luteum is preprogrammed to produce progesterone and estrogen for just fourteen days, after which time it begins to disintegrate. As it does, estrogen and progesterone levels drop sharply. Since without high levels of these hormones your spongy uterine lining cannot exist, it begins to disintegrate as well.
The Menstrual Cycle
The purpose of the menstrual cycle is to prepare the uterus, or womb, for possible pregnancy. During the cycle, the special endometrial tissue lining the inside of the uterus undergoes certain specific changes. It grows and thickens. Blood vessels and glands develop to provide a nourishing environment for the fertilized egg. The female sex hormones — estrogen and progesterone, secreted by the ovaries - are responsible for these changes. About the sixth day of the cycle, just after menstruation has ceased, the endometrium is no more than half a centimeter thick. Increasing levels of estrogen then induce the endometrium to grow so rapidly that, by the fourteenth day, it may be as much as ten times thicker than it was the week before.
The usual menstrual cycle is approximately four weeks long. Ovulation takes place in the middle of the cycle, on about day 14. The ovarian follicle breaks open to release the egg or ovum that has been developing in the ovary.
If the egg is fertilized, it completes its journey through the fallopian tube, passes into the uterine cavity, and attaches to the thickened endometrium on about day 22. Menstrual periods then cease until after delivery.
If the egg is not fertilized, estrogen and progesterone levels decline and the thickened endometrial tissue breaks down. Menstruation takes place as blood and endometrial tissue are discharged through the vagina. This completes one cycle; the reproductive organs are then ready for another cycle stimulated by the brain.
Why You Get a Menstrual Period
To help cleanse your system of this now needless tissue, your body begins to produce a series of biochemicals called prostaglandins. They help stimulate powerful uterine contractions that pull the excess tissue from the walls of your uterus and expel it from your body. It is the combination of this tissue and the blood from the tiny vessels that rupture during the extracting process that forms the basis of your monthly menstrual flow.
Although this process should cause only minimal discomfort, some of my patients report pain ranging from mild to severe accompanying every menstrual period. Why does this happen? It was recently discovered that when, for various reasons, a woman produces extremely high levels of prostaglandins, her uterus can contract so violently during the shedding process that painful cramping occurs just prior to every period.
With or without pain, however, from the moment your menstrual flow begins, the entire hormonal network is reactivated, and your body begins to prepare for another twenty-eight-day cycle — and a new chance to get pregnant.
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