Answering why it is important to know about the complete menstrual cycle is a much more subjective question than the first question. For people with periods, I think it is important to know about the full cycle because I think it is simply valuable to know and understand how and why a repeating body function occurs. For anybody else, I think it is important to know about because I personally think understanding the human body is an essential part of anyone's education.

A typical menstrual cycle lasts 28 days; however, there is variability in the length of the cycle. Some women's cycles are slightly shorter or longer, or even not always exactly regular. Starting with the first day of menstruation, the blood and tissue lining of the uterus breaks down over a period of 4 to 8 days. During this bleeding period hormone levels across the board are low.

Starting around day 5, a single follicle begins preparation for release. It grows, and estrogen levels begin to rise. The increased levels of estrogen cause the lining of the uterus to grow and thicken in preparation of receiving an egg.

Estrogen levels continue to rise until about day 14. At that point, there is a massive spike in FSH (follicle stimulating hormone) and LH (leutinizing hormone). This causes the mature follicle to burst and release an egg.

Following ovulation, the luteal phase begins, and the egg travels down the oviducts toward the uterus. Estrogen, FSH, and LH levels fall off and progesterone levels drastically increase. The progesterone helps maintain the uterine walls; however, if fertilization doesn't occur, the progesterone levels will fall off starting around day 24. The loss of progesterone will eventually cause the lining of the uterus to fall away, and the cycle starts over.