Development and fusion of the endocardial cushions.
D000818:Animals; D002642:Chick Embryo; D004699:Endocardium / Q000196:embryology* / Q000648:ultrastructure; D005855:Germ Layers / Q000502:physiology; D006346:Heart Septum / Q000196:embryology; D008855:Microscopy, Electron, Scanning