It's an interesting idea, but turbosquid is about the only place you're going to find ready-made models with that level of detail, and even then it's not very common. Reason being most software - even the high end software - isn't capable of handling the amount of geometry it would require to fill an entire scene where every model is detailed to that degree, so most 3D modelers only create the details that you will see on the surface and often fill in the small details with material shaders and texture maps whenever possible. There's very little reason to model in details of an object when those details will never be seen in the finished piece so they only serve as resource hogs. Consider also, that without being an engineer or having access to detailed blueprints and references, most 3D modelers don't really know what those hidden details even look like. There are a number of other factors to consider as well, such as the complexity of trying to rig a figure with a full vascular system. It can be done but since it's a specialized kind of project that most people wouldn't see a need for, it's not very common to find. So I think your best bet would be to commission said models, but that could cost you quite a bit. Some of us will model anything a client wants for the right price, as long as it's legal.