atrioventricular cushion morphology trait atrioventricular cushion orientation trait Any measurable or observable characteristic related to the location or arrangement in relation to each other and the developing heart of the mounds of embryonic connective tissue that bulge into the embryonic atrioventricular canal; these mounds eventually fuse to form the valves between the right and left atrioventricular orifices. Trait.ontology VT:0007038 endocardial cushion orientation trait