The usual time period of the menstrual cycle is 28–29 days, but this can differ between women and from their one cycle to the next one. The length and time of menstrual cycle is calculated from the very first day when the periods start till the day before the next period comes again.
Girls get their first period (menarche), on average, between the ages of 11 and 14 years.
The menstrual cycle is compounded structure and is controlled by various glands and the hormones that are formed by these glands. A brain structure which we call the hypothalamus effects the close by pituitary gland to form some certain chemicals, which then influence the ovaries to form the sex hormones like oestrogen and progesterone.
The menstrual cycle can be seen as a biofeedback structure, which means every system and gland is greatly affected by the activity of the other glands and structures.
Phases of menstrual cycle
There are four main phases of menstrual cycle:
1-menstruation
2-the follicular phase
3-ovulation
4-the luteal phase.
Menstruation
Menstruation is the eradication of the thickened layering of the uterus out of the body from the vagina. Menstrual fluid have blood in it, cells which are from the layering of the uterus (endometrial cells) and mucus. The normal length of a period is generally between three days and one week.
Follicular phase
The follicular phase begins on the first day when menstruation startsand itends with the ovulation. Influenced by the hypothalamus, follicle stimulating hormone (FSH) is released by the pituitary gland. This hormone stimulates the ovary to form about five to 20 follicles (tiny nodules or cysts), on which the surface beads on.
Each follicle have an immature egg in it. Normally, only one follicle can mature into an egg, whereas the others die. This can happen in a roundabout of 10 of a 28-day cycle.
Ovulation
The deliverance of a mature egg from the surface of the ovary is called ovulation. This normally happens mid-cycle, mostly in two weeks or so before the start of menstruation
During the follicular phase, the developing follicle causes a rise in the level of oestrogen. Thehypothalamus in the brain recognizes these rising levels and releases a chemical called gonadotrophin-releasing hormone (GnRH). This hormone prompts the pituitary gland to produce raised levels of luteinizing hormone (LH) and FSH.
Within two days, ovulation is triggered by the high levels of LH. The egg is funneled into the fallopian tube and toward the uterus by waves of small, hair-like projections. The life span of the typical egg is only around 24 hours. It will die if it doesn’t meet a sperm during this time.
Luteal phase
In course of ovulation, the egg breaks from its follicle, but the ruptured follicle rests on the exterior of the ovary. In the next two weeks, the follicle transforms into a structure known as the corpus luteum. This system begin releasing progesterone, with a little amounts of oestrogen. This blend of hormones maintains the thickened layering of the uterus, waiting for the egg to stick (implant) which is fertilized.
