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Menstruation
(Menstrual Cycle)

What is menstruation?

Menstruation is a woman's monthly bleeding, also called a period. When you menstruate, your body is shedding the lining of the uterus (womb). Menstrual blood flows from the uterus through the small opening in the cervix, and passes out of the body through the vagina. Most menstrual periods last from three to five days.

What is the menstrual cycle?

Menstruation is part of the menstrual cycle, which prepares your body for pregnancy each month. A cycle is counted from the first day of one period to the first day of the next period. The average menstrual cycle is 28 days long. Cycles can range anywhere from 21 to 35 days in adults and from 21 to 45 days in young teens.

Body chemicals called hormones rise and fall during the month to make the menstrual cycle happen.

What happens during the menstrual cycle?

In the first half of the cycle, levels of estrogen (the "female hormone") start to rise and make the lining of the uterus (womb) grow and thicken. At the same time, an egg (ovum) in one of the ovaries starts to mature. At about day 14 of a typical 28-day cycle, the egg leaves the ovary. This is called ovulation.

After the egg has left the ovary it travels through the Fallopian tube to the uterus. Hormone levels rise and help prepare the uterine lining for pregnancy. A woman is most likely to get pregnant during the three days before ovulation or on the day of ovulation. Keep in mind, women with cycles that are shorter or longer than average may ovulate earlier or later than day 14.

If the egg is fertilized by a man's sperm cell and attaches to the uterine wall, the woman becomes pregnant. If the egg is not fertilized, it will break apart. If pregnancy does not occur, hormone levels drop, and the thickened lining of the uterus is shed during the menstrual period.

Picture of the female reproductive system



Next: What is a typical menstrual period like? »

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Menstruation

What is normal vaginal bleeding?

Normal vaginal bleeding is the periodic blood that flows as a discharge from the woman's uterus. Normal vaginal bleeding is also called menorrhea. The process by which menorrhea occurs is called menstruation.

Normal vaginal bleeding occurs as a result of cyclic hormonal changes. The ovaries are the main source of female hormones, which control the development of female body characteristics such as the breasts, body shape, and body hair. The hormones also regulate the menstrual cycle. The ovary, or female gonad, is one of a pair of reproductive glands in women. They are located in the pelvis, one on each side of the uterus. Each ovary is about the size and shape of an almond. The ovaries produce eggs (ova) and female hormones. During each monthly menstrual cycle, an egg is released from one ovary. The egg travels from the ovary through a Fallopian tube to the uterus.

Unless pregnancy ...

Read the Vaginal Bleeding article »











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