part of part of heart endothelium cardiovascular system endothelium heart endothelium An endothelium that is part of a heart [Automatically generated definition]. BTO:0004293 UBERON:0008307 this class includes any endothelia that are part of the heart. This might include the endocardial epithelia, as well as endothelia of vessels that are considered strictly part of the heart (e.g. outflow tract). As a grouping class, this may lack utility, and pending review this class may be obsoleted. For annotation consider a more specific class. cardiac endothelium