Menstruation is one of the most important parts of the menstrual cycle. So, from school textbooks of biology it is known that the duration of the menstrual cycle is 28 days. However, it really is too generalized figure, since most often it is 26-35 days. The duration of each loop is counted from the first day of menstruation until the last day before the beginning of the next. It is also important to note that when it starts the girls for the first time is evidence that their body is prepared for reproduction. Most often this occurs before 14 years of age, but in some cases it is and in 17.

Many believe menstruation is only necessary in order to rid your body of excess blood, or to purify the body. However, in reality the process is more complex. So, in essence, menstruation is the rejection of the female body thickened layer on the mucous membrane of the uterus, which is accompanied by bleeding.

Inside the uterine cavity is covered in a layer of the endometrium, which is influenced by the different periods of the menstrual cycle. Thus, in the first half of the cycle under the influence of hormone called estrogen, developing follicle. At this time the endometrium is in the process of active growth, to prepare for acceptance of a fertilized egg. When the follicle Matures, it ruptures, releasing the egg which then moves to the fallopian tube. This process is called ovulation.

After ovulation becomes active another hormone – progesterone. Under its influence, the endometrium of the uterus ceases to grow, and things start to change secretory nature. In this cycle if conception has not occurred after 12 to 14 days, the progesterone level falls sharply, which exfoliate the upper layers of the mucous membrane of the uterus, thins the blood vessels and starts bleeding, with impurities of secretory secretions of the uterus. Its main function is to clean the uterus from the endometrial layer, which was ready to take the egg, but then started to flake off and also give the opportunity to develop a new education.