Hi,
I also saw King Kramers fantastic tutorial. As for you flowing through blood vessels idea…
Why not do it the same way Kramer did.
1: Create a cylinder in you 3d app.
2: modify/bend/stretch it into a long `distorted` cylinder/tube
3: colour it like the inside of the vein/atery and add a bump map for texture.
4: add lighting inside it at various places
5: place a camera inside it and keyframe its pos/POV
6: then just animate it along the inside of the cylinder and save the renders.
The result would be a journey down a vein/artery.
Add the blood cells etc either after or during and there you go.