the interfaces between mesenchymal and myocardial tissues in the developing avian heart show a profoundly different character in different regions of the heart : the interface between epicardial mesenchyme and heart wall myocardium is planar , without intermingling of the two cell types , whereas the interface between endocardial cushion mesenchyme and myocardium is diffuse , with extensive invasion of both tissue types across the border to produce intermingling of the two tissues .
C0018787
heart
C0027061
myocardium