Hi,
I wish I could provide the answer you are expecting, but there is no one program (in my opinion) that is more suited to medical animations. I've used LightWave for over 12 years and am most familiar with it, though I have had some little experience with Max and Maya (alot of my colleagues use Maya). And really it has very little to do with the 3D tool you are using as all of these are capable of producing great medical animations with the right person at the helm.
Unfortunately, you have your work cut out for you, as really good medical animations are probably a bit of a reach for someone with no experience with 3D animation. I've done a number of ones similar to yours (though mine were breathing, diaphraghm, rib cage, trachea & esophageal, etc) and before I started I talked to a studio out of Australia who were very friendly, and have done seemingly good work from what I have seen - but given my experience and their prices, I decided not to farm it out to them. They are here:
http://www.medical-animations.com/
I would suggest you talk to them if you have the budget as I believe, unless you have a solid foundation in modelling, rigging, animation & particle systems - not to mention texturing for those cool cutaways and see-through looks associated with some of the best medical animations, it's going to be tough to pull-off and have it look any good.
Alot of the issues really tend to be with sourcing really good (and easy to work with - i.e. clean geometry, nice texturemapped names etc) 3D models of the body parts and organs - sure you could model them yourself, but for ultra-realism and scale it would probably be best to get the organ models from people who have real medical scans who have converted those datasets to nice models for the 3D package you are using.
You can buy the models from some places online - they tend to be expensive, so it may be cheaper to farm out the work instead. But, if you don't have the budget to do it the realistic ("right") way, then I'd suggest simplifying the animations to almost 2.5D diagrams of simple shapes with simple pre-scripted animations of arrow movements, valves pumping etc. Otherwise, you'll spend way too much time trying to rig something generic, model something very complex and organic and hours texturing them to get just the right look - not counting the time it would take to do cool cutaways and transparencies etc.
For your needs, and the fact that depending on your background, the time it would take a 3D novice to upskill enough to pull off the kind of animations you are talking about would be more than significant. That's why if you can deal with limited 2D or very simplistic 3D representations of the effect you are talking about for your educational movies, then it would be far easier to do that.
As far as your answer regarding LW vs Maya etc. I have used both (more LW than Maya obviously) and I like it and find it the more intuitive, but it really doesn't matter, they are both mature products and have the abilities to do what you ask. It really boils down to it being the painter and not the brush / the author's words and not the pen... :)
hope that helps a bit,
Sam
