What is the point of a woman having a period?

Female reproduction is a complex process. It takes a lot of time and effort for the body to be fertile, and actually grow a baby from scratch. Anything that takes this much time and energy is going to be felt by your entire body.

Why do we bleed?

Because the uterine lining has to be refreshed. If not, it will be a breeding ground for bacteria. Any time that much blood sits around - even contained - there's a potential for rot and infection. You flush it out and start new every month to keep you healthy and so that you have the best chance at pregnancy the next month. I do mean "flush". All that blood leaving your body also cleanses your vagina. This is important because if you've been having sex, you have the potential to have bacterial infections in there. It's been proven that periods prevent and control bacteria "down yonder".

Cramps?

Your system uses uterine contractions to squeeze out the period blood. Like a fist around a water bottle. Fun, right?

You'll also notice swelling and mood swings. That's because Mother Nature hates us and wants us to suffer. No, just kidding.

Firstly, if you're using birth control then you actually don't menstruate at all any more - the bleeding you get is withdrawal bleeding, and it's a completely different process to menstruation.

We menstruate because our body needs to ready itself for pregnancy - every month uterus lining builds-up in preparation for pregnancy so that the fertilised egg has somewhere to implant within the uterus, if you don't fall pregnant then the uterus lining is no longer needed so it sheds.

Pain isn't a normal part of menstruation, although many women get cramps most women can completely prevent them with simple dietary changes or herbal treatments - for many of us periods feel absolutely fantastic as they come with other changes like increased senses, increased sexual arousal, better moods, creativity, better mental equity, etc. With cramps specifically it's the uterus contracting to force out the uterus lining that's no longer needed, some people (either naturally or due to ill-health) are more sensitive to the hormones responsible for triggering these cramps.

More information:

On The Rag: A Guide To Menstruation - http://www.scarleteen.com/article/body/on_the_rag_...

Two weeks before a girl's period, her tubes release an egg. This egg will be available for fertilization (by sperm, you know) for a couple days I think? During that time a thick layer of skin and blood build up around the uterus- if the girl gets pregnant, the baby will be protected (or something?) by this tissue. If she doesn't get pregnant, then the tissue needs to be shed- hence your period. It hurts because the uterus is squeezing itself to empty itself out.