There are countries who specialized in breeding arabians, and that is reflected in their unique characteristics, Polish lines with Raffles, They have state run studs, and they have rounder, larger boned type of arabs.
Egyptian, which are very refined, usually like grey hounds, thin, long and some what narrow chested.
Spanish, which are some what undistictive, but I have heard some what more like Andulusians in looks but typy like a typical arab.
Russian, which are tall, and with good legs, not so round, and not as nice of heads. BUT nice minded horses.
Crabbet lines, which are either american or english, some what stockier, and "old fashioned" looking...
There are a LOT of mixing now adays... such as the refined heads of the egyptians on the body type of the polish...
The original arab breeding goes back more than 2500 years, the TB wasn't really created until the 1700's or there abouts.
The Byerley Turk, the Goldophin arabian, and the Darley arabian are the original "eastern or oriental blood" of the TB...
http://www.diamondcrestinc.com/FoundationSires.html