I get why the rim of the cup should not go past your cervix b/c otherwise it's like pouring coffee down the side of a mug, but I'm not sure I get the "around" the cervix (O) metaphor. If I am imagining this metaphor (or my physiology) wrong, please enlighten me! As I imagine it, a cervical cap (which I used to use, many many years ago) goes "around" the cervix, like a hat being worn atop the cervix--the rim of the cervical cap actually is "around" the entire cervix. I understand that some women may wear their cups in this way (or partially in this way), depending on the particular woman and the shape of the cup, but I thought that the cervix is more like a mound sticking down off the "roof" of the vagina (more or less), isn't it? I can reach the half of my cervix that faces the vaginal opening, but the other half is too far in--the tip of my cervical "mound" doesn't point directly toward the vaginal opening, but more toward the lower vaginal wall. I gather that some ladies' cervices (cervixes?) point toward one side, or might point more toward or away from the vaginal opening than my own, so maybe that's why I'm having trouble imagining this. When my cup is in, its base points generally down toward the entrance to the vagina--actually, the base of the cup rests against the upper wall of my vagina, just above my urethra, which means that the rim of my cup isn't "around" my cervix at all. At least I don't think it is. I imagine the rim of the cup sealing against my vaginal walls, all the way around, and one part of the rim rests against the edge of my cervical "mound" that is closest to the opening of my vagina, which is what stops it (a) from leaking and (b) from going up any farther inside.
I watched that youtube video of Melissa's, where she uses a long slender wine glass with a little cervix-bump in it to illustrate cervical position and inserting and removing a cup (this one: http://www.youtube.com/watch?v=3NDol9HZftQ -- thanks, Melissa!). So the metaphor in my mind is like a tunnel with a mound (giant ant-hill?) on the ceiling, taking up maybe half(?) the tunnel's diameter, and the cup goes in with the base pointed more or less toward the tunnel's entrance and the rim sealing against the tunnel walls, and when the edge of the cup's rim hits the mound's edge that is closest to the entrance of the tunnel, that's as far in as the cup can go. If the cup goes up too high (i.e., part-way up the ant-hill, or even past the top of the ant-hill), then it is obviously not going to seal against the tunnel walls anymore and will leak (the "pouring coffee down the side of the mug" concept).
So is the way I imagine my cup to be working the same thing as "around" the cervix? I'm confused. Maybe it is, and it's just a difference in terminology, or maybe some women's cervixes point more directly toward the vaginal opening than mine so they really are wearing it "around" the cervix, but having used a cervical cap and also a cup, the (O) concept isn't making sense to me. Help?