Menstrual Cycle

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Menstrual Cycle
Menstrual Cycle. Ovulation

The first menstrual cycle (also menarche) is a sign of a girl turning into a woman. Menstruations (menstrual bleeding) appear in the early adolescence, they indicate that a woman is fertile and ready to bear children. Every month, complex hormonal changes occur in a woman‘s body. The result of these changes is a mature ovum (also called an egg). At the same time, the uterus prepares itself for implantation of the embryo - the beginning of a new life. All of the changes, occurring in a woman during one month, are called the menstrual cycle. Even though one menstrual cycle is considered to last one month, its actual length is 21-35 days (28 days being the average). The first day of the cycle is the day when menstruations start. The menstrual phase of the cycle usually lasts 2-6 days and the average blood loss is 20 to 60 ml.

Ovulation usually happens on the 14th day of the cycle. During ovulation, a mature egg is released from the ovary, into the fallopian tube (salpinx). The egg remains fertile for only 2 days. During that time the woman‘s hormonal system ensures the best conditions for the spermatozoa to reach the egg. To do that, the spermatozoa must pass through the cervix, up along the uterus, to the salpinges, where only one spermatozoid fertilizes the egg. The hormones also make women more attractive to men, as well as the other way around.

If fertilization happens, a zygote is formed, which turns into a blastula and implants into the uterine wall (which is thickened and ready to feed the embryo up to 12 weeks, until the formation of the placenta). The fetus stays in the uterus for 9 months, until birth.

If fertilization does not happen, the level of female hormones drops and approximately 2 weeks after the ovulation, the upper layer of the uterine mucosa starts shedding. Small bits of the mucosa (also the unfertilized egg) mix with some blood from small vessels, as well as the fluid inside the uterus and the mucus of the cervix, and are secreted through the vagina. That defines the start of the menstrual cycle. Even before the menstruations start, the development of other eggs in the ovaries has begun. The hormone synthesis increases and the whole cycle starts all over again.

The normal human menstrual cycle begins when a girl is 12 to 14 years old. A woman remains fertile until menopause. The average age of menopause is 50 years.

Throughout the lifetime a woman experiences about 400 menstrual cycles. Cyclical hormone-controlled changes are only inhibited during pregnancy and lactation. During that time, eggs do not mature in the ovaries and menstruations do not start. Today, the cause of good health in women with multiple children, who have breast-fed them for a long time, is clear. Constant inhibition of cyclic changes protects from ovarian cysts and cancer as well as uterine mucosal cancer, also, excessive menstruations, which might cause anemia and weaken the body. With the discovery of hormonal contraception, this opportunity is widely used by women all over the world, who only have 1-2 children.


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