Approximately every twenty eight days women of child bearing age drop an egg in the hopes that it will be fertilized by the male spermatozoa. This process is under hormonal control. If the egg is fertilized by the male, she becomes pregnant. If the egg is not fertilized, her menstrual period begins.
When a female has her menstrual cycle, her body is ridding itself of the shed uterine lining. The uterus in the female prepares itself for implantation of the fertilized egg. When this doesn't occur, the uterine lining is shed as the menstrual cycle. Contained in the discharge of the menstrual cycle are blood cells, and the remnants of the uterine lining.
Beginning at puberty and continuing until menopause, the menstrual cycle occurs each month. This cycle is approximately 28 days, although it may be slightly longer or shorter in some women. During this monthly cycle, the uterine lining, under the influence of hormones thickens. In the event an ovum(egg cell) is fertilized in the oviduct, this egg will eventually travel to the uterus and implant in the uterine lining and continue to develop until birth. However, if the egg that month is not fertilized, it will disintegrate. The uterine lining which is no longer needed, will break down and be shed. This is called menstruation. After menstruation, the cycle will repeat the following month and every month thereafter during a woman's reproductive years. The only time the menstrual cycle ceases during this time frame, would be when a woman is pregnant.
When a woman menstruates, the lining of the uterus is being shed and this is why there is bleeding. The reason that this happens is because she did not become pregnant during the menstrual cycle. In other words, a fertilized egg was not implanted in the uterus.
Certain hormones that are responsible for keeping women healthy are regulated during the menstrual cycle as well. An example is estrogen, which helps bones to be strong and healthy.
The cycle starts on day 1 of the first period and starts over again on day 1 of the next period. An average menstrual cycle lasts for 28 days, although this varies.
The purpose of the menstrual period (if you mean just the part when a woman is actually menstruating) is to get rid of the lining of the uterus in the event that no child is conceived during that particular cycle.
Each month, a woman's body prepares her uterus to receive a fertilized egg. The uterus must build up a lining in which the embryo would rest and from which it would get its first nutrition if it were to be fertilized. If no egg is fertilized (if the woman does not become pregnant) there is no need for the lining of the uterus and it must be expelled.
Please follow the link for a more detailed discussion of this topic. The discussion includes a more detailed description of what happens during the rest of the menstrual cycle.
About once a month, a tiny egg leaves one of the ovaries — a process called ovulation — and travels down one of the fallopian tubes toward the uterus. In the days before ovulation, the hormone estrogen stimulates the uterus to build up its lining with extra blood and tissue, making the walls of the uterus thick and cushioned. This happens to prepare the uterus for pregnancy: If the egg is fertilized by a sperm cell, it travels to the uterus and attaches to the cushiony wall of the uterus, where it slowly develops into a baby.
If the egg isn't fertilized, though — which is the case during most of a woman's monthly cycles — it doesn't attach to the wall of the uterus. When this happens, the uterus sheds the extra tissue lining. The blood, tissue, and unfertilized egg leave the uterus, going through the vagina on the way out of the body. This is a menstrual period. This cycle happens almost every month for several more decades (except, of course, when a female is pregnant) until a woman reaches menopause and no longer releases eggs from her ovaries.
Just as some girls begin puberty earlier or later than others, the same applies to periods. Some girls may start menstruating as early as age 10, but others may not get their first period until they are 15 years old.
The amount of time between a girl's periods is called her menstrual cycle (the cycle is counted from the start of one period to the start of the next). Some girls will find that their menstrual cycle lasts 28 days, whereas others might have a 24-day cycle, a 30-day cycle, or even longer. Following menarche, menstrual cycles last 21-45 days. After a couple of years, cycles shorten to an adult length of 21-34 days.
Irregular periods are common in girls who are just beginning to menstruate. It may take the body a while to sort out all the changes going on, so a girl may have a 28-day cycle for 2 months, then miss a month, for example. Usually, after a year or two, the menstrual cycle will become more regular. Some women continue to have irregular periods into adulthood, though.
Menstruation (a period) is a major stage of puberty in girls; it's one of the many physical signs that a girl is turning into a woman. And like a lot of the other changes associated with puberty, menstruation can be confusing. Some girls can't wait to start their periods, whereas others may feel afraid or anxious. Many girls don't have a complete understanding of a woman's reproductive system or what actually happens during the menstrual cycle, making the process seem even more mysterious.
When girls begin to go through puberty (usually starting between the ages of 8 and 13), their bodies and minds change in many ways. The hormones in their bodies stimulate new physical development, such as growth and breast development. About 2 to 2½ years after a girl's breasts begin to develop, she usually gets her first menstrual period.
About 6 months or so before getting her first period, a girl might notice an increased amount of clear vaginal discharge. This discharge is common. There's no need for a girl to worry about discharge unless it has a strong odor or causes itchiness.
The start of periods is known as menarche. Menarche doesn't happen until all the parts of a girl's reproductive system have matured and are working together.
Menstrual period is the period during which menstruation takes place.
Menstruation as a periodical occurrence bodies of all women of child bearing age which occurs about once a month, varying between 24 to 32 days. During menstruation women loose blood and cells that build up in the lining of a their uterus. Thickening of the lining of uterus prepares it for pregnancy. When Pregnancy does not takes place for within a certain period, the the lining breaks down, and blood and cells are discharged through the vagina. This process of menstruation, that is flushing out of blood and cells from the uterus lasts from three to seven days. This period is called the menstrual period or menses.