part of develops from ends during starts during heart epicardium xenopus_anatomy XAO:0000316 The inner layer of the pericardium that is in contact with the surface of the heart. During cardiac development, it is the source of multipotent mesenchymal cells, which give rise to endothelial and smooth muscle cells in coronary vessels and also, possibly, to cardiomyocytes. UBERON:0002348 heart epicardium heart primordium death tissue epicardial precursor cell NF stage 27