sinoatrial node morphology trait sinoatrial node molecular composition trait 2024-04-15T13:00:50Z Any measurable or observable characteristic related to the proportions of proteins, minerals, nutrients, gases, or other substances in the small mass of modified cardiac muscle fibers located at the junction of the superior vena cava and the right atrium that is the source of contraction impulses for the heart. SA node molecular composition trait Trait.ontology VT:0011112 caripark pacemaker molecular composition trait