can't update from itunes 7.6 to itunes 8

Hey, this is probably a simple enough problem to solve, but I can't update my itunes on my mac. Right now it's itunes 7.6. I want to get itunes 8, but every time I ask it to update, it reroutes me to the software update application which, in turn, doesn't show itunes on the list of possible updates. I'm not ignoring any updates, so what gives? All help is very much appreciated.