The Menstrual Cycle
Menstruation is defined as the discharge of blood and tissue from the lining of a woman's uterus every month. Many women refer to this as getting their menstrual period, or "period."
Menstruation has been known to begin as early as the age of 8 years or as late as 16 years, but most often starts at around the age of 11 or 12 years. There are four stages of puberty. Menstruation is the fourth and final stage. In general, though not always in this exact order, there will first be a growth spurt, followed by the growth of hair under the arms and around the pubis (pubic hair), breast development, and then 2 to 2 1/2 years later, menstruation.
Some 6 months prior to the first menstrual period, a girl may notice an increased discharge of clear mucus from her vagina. This is normal.
The first menstrual period is called the menarche. The menarche will not occur until every part of a girl's reproductive system has matured and is functional. The menarche can be quite mild in nature. In some cases there may be only a few drops of blood or perhaps a bit of spotting.
Many girls have a regular menstrual cycle, every month, right from the beginning. Other girls may skip a month or have two menstrual periods within the same month. All of these scenarios are normal for the early months of menstruation. It may take quite some time for the menstrual period to become a regular monthly event.
Once menstruation has begun, a girl has entered her fertile years and is now capable of conceiving and bearing a child. As a girl matures, her brain signals her body to produce hormones which serve as a trigger for the menstrual cycle. Part of this cycle is the monthly menstrual period.
The average length of the menstrual cycle is from 28-30 days. The counting of the cycle begins from the first day of one period until the first day of the next. It is normal for a cycle to last as few as 21 days and as long as 35 days.
Five days into the cycle, the lining of the uterus, or endometrium, starts to thicken. This is the body's way of preparing to carry a developing fetus (baby growing inside the mother's uterus), should the woman become pregnant.
At about 14 days into the cycle, an egg is released from one of the ovaries. This is known as ovulation. The egg moves into the closer of the two fallopian tubes that are connected to the uterus. There the egg awaits fertilization by a man's sperm. If the egg is fertilized, it moves into the uterus, attaches to the lining, and starts to develop as a fetus.
At around 28 days into the cycle, if the egg has not been fertilized, the endometrium is shed as a mix of blood and tissue and is jelly-like, thick, and dark red. This is called menstrual blood. The menstrual blood flows from the uterus (womb), down to the cervix (opening of the uterus), into the vagina, and out of the body. This bleeding is the menstrual period and lasts from 3-5 days. The menstrual period may last up to 7 days. Then the cycle begins anew.