The onset of menstruation indicates that a woman is ready to bear children. Menstruation is a biological routine most women experience regularly; yet it's a mystery, and in some societies, the subject is taboo. This article is intended to clear up this mystery.

Menstruating women might have periods (cycles) of differing durations in the course of a lifetime.

Your menstrual cycle can be divided into four menstrual phases or stages:

(i)The menstrual phase -- Day 1 - 5
The menstruation flow is normal for the first 3 - 5 days. In some cases, this phase can range from 2 to 7 days. The bleeding in this phase is not just all menstruation blood; some of its is uterus lining the body doesn't need, and discards.

(ii)The follicular phase -- Day 6 - 14

During this period, cells grow inside little cavities (follicles) and eventually become eggs. It is one of these eggs and a male's sperm that combine to make a baby.

Menstruation hormones (Follicle Stimulating Hormone - FSH and Luteinizing Hormone - LH) are released into the bloodstream. The ovaries are where a woman produces eggs. The purpose of the first hormone (FSH) is to stimulate the ovaries to produce eggs. And the purpose of the second (LH) is to signal the ovaries to release an egg.

(iii)The ovulation phase -- Midpoint (Day 14)
During this phase, which is about the 14th day of your menstrual cycle, there is a sudden increase in the level of the second hormone (LH). This is the cue for the sac (follicle) containing the most mature egg to release it, for its journey down the fallopian tube. It is during this phase that a woman is most likely to become pregnant.

(iv)The luteal phase -- Day 15 - 27
Around 20 eggs develop and the most mature egg gets released. While the eggs are developing, the sacs produce estrogen. And just before the most mature egg gets released, progesterone is also secreted in addition to estrogen.

Estrogen increases the flow of blood to the uterus during the menstrual cycle period, and helps thicken its lining. Progesterone helps produce substances that will nourish a fertilized egg implanted in the lining.

If fertilization takes place, the ruptured sac, after the egg has broken through (Corpus luteum), continues to produce progesterone, aimed at nourishing the growth of the embryo. Progesterone blocks the release of further eggs, till the pregnancy is terminated.

Estrogen, while regulating progesterone, begins a major process of fetal maturation. Without estrogen, the lungs, liver and other organs and tissues cannot mature.

If fertilization does not take place, estrogen and progesterone levels drop. Without these hormones, the lining of the uterus breaks up and is released through the vagina, to mark the onset of the menstrual cycle period.

Once the uterine lining is shed, your menstrual cycle begins anew.