what is periods ?why does it occur ?
453444
From http://en.wikipedia.org/wiki/Menstrual_cycle\n\nOnly human beings and the great apes experience a true menstrual cycle. Most placental mammals experience estrus instead. The menstrual cycle is under the control of the reproductive hormone system and is necessary for reproduction. In women, menstrual cycles occur typically on a monthly basis between puberty and menopause.\n\nDuring the menstrual cycle, the sexually mature female body releases one egg (or occasionally two, which might result in dizygotic, or non-identical, twins) at the time of ovulation. The lining of the uterus, the endometrium, builds up in a synchronised fashion. After ovulation, this lining changes to prepare for potential implantation of the fertilized egg to establish a pregnancy. If fertilization and pregnancy do not ensue, the uterus sheds the lining and a new menstrual cycle begins. The process of the shedding of the lining is called menstruation. Menstruation manifests itself to the outer world in the form of the menses (also menstruum): essentially part of the endometrium and blood products that pass out of the body through the vagina. Although this is commonly referred to as blood, it differs in composition from venous blood.\n\nCommon usage refers to menstruation and menses as a period. This bleeding serves as a sign that a woman has not become pregnant. (However, this cannot be taken as certainty, as sometimes there is some bleeding in early pregnancy.) During the reproductive years, failure to menstruate may provide the first indication to a woman that she may have become pregnant. A woman might say that her "period is late" when an expected menstruation has not started and she might have become pregnant.\n\nMenstruation forms a normal part of a natural cyclic process occurring in healthy women between puberty and the end of the reproductive years. The onset of menstruation, known as menarche, occurs at an average age of 12, but can occur any time between the ages of 8 and 16.[1] However, the condition precocious puberty has caused menstruation to occur in girls as young as 8 months old. The last period, menopause, usually occurs between the ages of 45 and 55. Deviations from this pattern deserve medical attention. Amenorrhea refers to a prolonged absence of menses during the reproductive years of a woman for reasons other than pregnancy. For example, women with very low body fat, such as athletes, may cease to menstruate. The presence of menstruation does not prove that ovulation took place; women who do not ovulate may have menstrual cycles. Those anovulatory cycles tend to take place less regularly and show greater variation in cycle length. In addition, the absence of menstruation also does not prove that ovulation did not take place, because hormone disruptions in non-pregnant women can suppress bleeding on occasion.\n\nWomen show considerable variation in the lengths of their menstrual cycles, and the length of the menstrual cycle differs in different animals.\n\nWhile cycle length may vary, 28 days is generally taken as representative of the average ovulatory cycle in women. Convention uses the onset of menstrual bleeding to mark the beginning of the cycle, so the first day of bleeding is called "Cycle Day one".\n\nOne can divide the menstrual cycle into four phases:\n\nMenstruation\nEumenorrhea denotes normal, regular menstruation that lasts for a few days (usually 3 to 5 days, but anywhere from 2 to 7 days is considered normal.[2] The average blood loss during menstruation is 35 millilitres with 10-80 mL considered normal;[3] many women also notice shed endometrium lining that appears as tissue mixed with the blood. An enzyme called plasmin — contained in the endometrium — inhibits the blood from clotting. Because of this blood loss, women have higher dietary requirements for iron than do males to prevent iron deficiency. Many women experience uterine cramps, also referred to as dysmenorrhea, during this time
589482
Stress can TOTALly mess your period up as can unhealthy eating, smoking, excess drinking, drugs....be careful to get enough sleep and take in healthy things to your body.\n\nTry some stress reducing exercises,too.\n\nBut all this should be AFTER regular exams and a pap smear to rule out anything else.\n:)\n\nDO NOT get onto birth control to regulate periods if you don't know the cause! That is simply dangerous and can cover-up and underlying problem. A friend of mine did that and almost died because she actually had a cyst on an ovary that exploded and made her very ill.
156927
Yes. Any ill health, physical, emotional or psychological stress can cause menstrual irregularities.
407636
Rags, that's why periods are called "being on the rag".  They also made something like a sumo wrestler's outfit that you strap onto your waist and attaches to the rag that you wear, you have to remember people also didn't have underwear like we do now back in the day.
13778
A period is the amount of time it takes for an oscillating (repeating) function or phenomena to complete one cycle of behavior.  This might be the amount of time it takes a wheel to make a full revolution, or the distance between two identical points on the graph (peaks or troughs) for a trigonometric function, such as sine or cosine.
1073124
It is most likely that you are pregnant, of which you should see your doctor for a blood test, as this is the most accurate way of testing.  Other reasons for period abnormalities include stress, hormonal imbalance, thyroid, weight gain/loss, polyp, cyst, amongst other reasons.  Please see your doctor for an exam and testing.
67532
You should seek professional help if it happens often. If it is just a one time case, no need to worry. Girls who starts having menstruation may need some time to reach a regular cylcle. Women who almost come to menopause stage also have irregular cycles. Many people have irregular menstrual cycles, it is hormonal and as long as no other things wrong with their bodies, they shouldn't worry too much. Excessive worry may cause health problems.
810756
The menses is a sloughing off of the uterine walls that are ready for a fertilised egg to imbed in the uterus. Once this occurs the menstrual cycle ceases. If the sloughing off were to happen it would be a miscarriage.
19215
Have you had a menstrual period before?\nIf this is the first time ever, then get a pad - ask an older female friend/confidant to explain this in person.\n\nIf you've had periods before, and this is an irregular occurence, then you absolutely should see a doctor.
672442
It has nothing to do with your period. I assume you are still young. At your age your period will not be completely regular yet. For a lot of woman their period will never be completely regular. Don't worry about it.
584376
It is perfectly normal to have irregular periods.  If you have alot of stress it happens, or if you exercise too much, or don't eat properly, or you can be perfectly healthy and its genetic.  Ask your mom if she was that way.  It is slightly possible it is problem like cysts so you should definately talk to your doctor.  She'll be able to figure out if it is a problem or if it is natural for you.  If it really bothers you, you can go on the Pill, which will make your periods lighter and as regular as clockwork (I literally get mine at 9am on the Wednesday they are due!)  So, there's nothing much to worry about since you are young, but talk to your doctor and go on the Pill if it bothers you alot.
719905
Periodic???\n\nTake Periodic as a dictionary word. This reflects a cyclic repetition.\n\nIn case of elements periodic means repetition of properties after a complete cycle.\n\nMendeleev and other scientists found that there is a repetition of properties of elements after eight elements so initially a period of eight elements was formed.\nTransition elements were inserted on a later stage.\n\nThe horizontal columns are called periods because they represent the cycle of PERIODICITY OF PROPERTIES OF ELEMENTS.\n\nGroups are called groups because they contain elements of similar properties; as obtained because of periodicity.
400658
One word, hormones.  They come during periods, before periods, during pregnancy, menopause, after a birth of a child...always.  It is part of the joy, and curse, of a woman!  ;)
409982
Are you talking about your period?  If so, this is most likely due to the stress you were going through.  Stress does all sorts of things to the body, and it can definitely mess with a woman's cycle.  If your cycles don't return to normal, though, you should see a gynocologist to make sure there is nothing else causing it to be irregular.
270137
hormone fluctuations...  plus they don't have to worry about getting pregnant since ovulation  happens  after the period, and you have to be ovulating to get pregnant.
498060
Heavy periods.  You should see your doctor for a diagnosis and treatment.
168722
Migraine symptoms in women can be triggered by changes in estrogen that occur during menarche, menstruation and menopause.1 The term "menstrual migraine" specifically refers to a migraine that occurs near the start of the menstrual cycle, in response to falling levels of estrogen. Oral contraception, hormone replacement therapy, and pregnancy can all affect migraine patterns