My daughter is swcah and turning 12 in a couple of days.  She started being interested in all that early too.  She was about 7 I think.  Since everyone was always doing something in her private area she wondered what that was used for anyway and why did she even need to have hers "fixed" as she put it.  She was severely verilized and the urethera was way up high and some other things and not to get into too much there I explained simply what it was for.  I told her when she becomes a woman like me she will use that part of her body to make a baby and then the baby comes out from it, when she is a woman.  The make a baby part was explained that women and men love on each other and their bodies make the baby.  I didnt exactly tell her well you know....  A great book and she still reads it sometimes is by American Girl and its The Body Book.  Great explainations about periods, hygiene, ect.....

I am so glad we are past that and onto our preteen years......HAHAHA...

Good Luck!