Depends on what dictionary you use

I have The American Heritage Medical Dictionary. Some say just muscle tissue formation and some specify at an embryonic level, a lot of the Vet dictionaries use this definition as does Wikipedia.
I know where you are coming from and I don't take offense.
I always come off as extremely argumentative and may seem aggressive in my statements. It's all good though, we are here to learn as am I. If I believe in something I will argue that it is right and if enough logical information is presented I leave the discussion enlightened! This happens a lot and is beneficial!