Sinoatrial node
Sinoatrial node
Definition
WP:Heart states: "The SA node is found in all amniotes but not in more primitive vertebrates. In these animals, the muscles of the heart are relatively continuous and the sinus venosus coordinates the beat which passes in a wave through the remaining chambers. Indeed, since the sinus venosus is incorporated into the right atrium in amniotes, it is likely homologous with the SA node. In teleosts, with their vestigial sinus venosus, the main centre of coordination is, instead, in the atrium.". Note however that ZFA has SA node.
Also known as cardiac pacemaker, Koch's node, node of Keith-Flack, nodus sinuatrialis, SA nodal muscle tissue, SA node, sinoatrial node, sinu-atrial node, sinuatrial nodal muscle tissue, sinuatrial node, sinus node, sinus node of Keith and Flack — per UBERON
The Sinoatrial node is a part of the Cardiovascular.