Anatomical heart sculpted in ZBrush. I made this accurate to the best of my ability but obviously the interior is hollow unlike a professional medical heart model.
I originally sculpted this at life size, but scaled it down by about 25% to save money on material costs. The pictures you see are the Frosted Ultra Detail via Shapeways (http://shpws.me/IF2n), which gives it a nice transparency affect. I'm not sure how this would come out a FDM printer but I'd love to see someone give it a shot!
I made this via Shapeways in the Frosted Ultra Detail material. No guarantees about how an FDM printer might deal with this. The thinnest wall is .8mm I believe.