part_of part of part of has part has part has_part composed primarily of musculature of body cardiac muscle tissue myocardium http://upload.wikimedia.org/wikipedia/commons/6/6e/Glanzstreifen.jpg TODO - check 'Myocardum proper' in FMA. We superclass the more generic class for now. FMA has is_a muscle layer - should we add this? ZFA and BTO both have is_a 'cardiac muscle' (tissue?). But in U we also follow FMA and have cardiac muscle tissue of myocardium (there is also Fibrocollagenous connective tissue of myocardium), which would be identical (see issue-10). Note that GO also treats left/right ventricular cardiac muscle tissue synonymous with ventricular myocardium myocardial conducting system of heart heart layer layer of muscle tissue