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The Epic Interactive Encyclopedia 1998
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Epic Interactive Encyclopedia, The - 1998 Edition (1998)(Epic Marketing).iso
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Menstrual_cycle
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1992-09-03
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The cycle that occurs in female mammals of
reproductive age, in which the body is
prepared for pregnancy. At the beginning of
the cycle, a Graafian (egg) follicle develops
in the ovary, and the inner wall of the
uterus forms a soft spongy lining. The egg is
released from the ovary, and the lining of
the uterus becomes vascularized (filled with
blood vessels). If fertilization does not
occur, the corpus luteum (remains of the
Graafian follicle) degenerates, and the
uterine lining breaks down, and is shed. This
is what causes the loss of blood that marks
menstruation. The cycle then begins again.
Human menstruation takes place from puberty
to menopause, occurring about every 28 days.
The cycle is controlled by a number of
hormones, including oestrogen and
progesterone. If fertilization occurs, the
corpus luteum persists and goes on producing
progesterone.