Creating animated "blood" inside a glass sphere

Related image: http://www.wallpaperup.com/uploads/wallpapers/2013/01/11/28815/big_thumb_c234b8e8cad3c824ea77578b4deed4e0.jpg

How would one start with creating this effect? I want the red inside of the sphere to move in a similar fashion to bands of silk, with lack of better words.

EDIT: Typo