Anatomy of the sinus node, AV node and os cordis of the beef heart

Abstract The bovine sinus node is in a location similar to that in the human and canine hearts, but it contains no central large artery whereas the sinus node in the other two species is distinctly organized about such an artery. This suggests the bovine sinus node may function as a more primitive structure. The arterial supply of the bovine sinus node originates from the proximal left circumflex artery. The AV node and bundle are similar in all three species in location and internal anatomy. The human and bovine AV node and bundle are supplied by a single artery entering from the posterior wall of the heart, while the dog has an equally large branch to this region from the septal artery. The os cordis is a large constant bone lying near the junction of the interatrial and interventricular septa of the beef heart and extending anteriorly into the AV valve rings, especially the right. The AV node lies parallel to the os cordis on its right atrial side and the AV bundle courses beneath the bone. Possible functions of the os cordis are considered.