mac os x and environement variables / paths

What sequence of configuration files lead me to the environment when I open up a terminal or shell on MAC OS X?

I’m confused by how the operating system PATH environement variable gets set.
I use bash as my shell…

I have:
~/.MacOSX/environment.plist
~/.bash_profile /// seems to have been moved aside by mac ports…
~/.profile
/masterbash_profile
/masterbash.bashrc

Help?