Abortion Amendment (updated below - Update II - Update III)

I'm probably having a senior moment, but can someone explain to me how the abortion amendment to the health care reform (HCR) bill works?

What I think I'm not understanding is, if you are a conservative Dem or a GOP member and you don't really want HCR to pass, but if it does pass you want an abortion restriction included in the bill, doesn't that mean that in voting for the amendment you are actually voting for the bill? What application does the amendment, separated from the HCR bill itself, have? The HCR bill and the amendment would seem to go hand in hand. I'm not getting how the Repubs/conserv Dems could have their anti-choice amendment attached to a HCR bill they didn't vote for.

Thanks for your patience.

Update: I think I get this now. Once upon a time I think understood that this is how it worked, that amendment votes were separate from final passage votes, but it just didn't compute for me today. It's pretty effed up that a gang of misanthrops aided and abetted by the majority party, can muck up a bill and then walk away from it without facing any accountability for the final product.

Update II: An Andrew Sullivan reader highlights the abortion-restriction procedures already included in the bill before the amendment was passed, and what added restrictions the amendment demands. It's becoming more and more clear what a poison pill this amendment was.

Update III: Via Digby, Americablog asks an intriguing question of anti-choice congresscritters who receive insurance lobby money.