Netilat Yadayim

Question

I was wondering about the concept behind washing before bread. Clearly, the purpose cannot be to remomve tuma, because simply washing with water isn't sufficient! If it's to simply clean your hands, then why the emphasis on the number of times and method of washing and not a requirement to use soap!!? The bracha does not refer to any type of washing but to "raising the hands"! I remember seeing a gemara (but don't remember where) that hands are considering askaniyot and therefore "dirty"?! So where is the origin of the beracha of netilat yadayim and why do we have to wash our hands and make that bracha before bread?