The sheep heart: Coronary and conduction system anatomy with special reference to the presence of an os cordis

Abstract

Abstract Each of the major coronary arteries of 25 fresh sheep hearts was injected with a different colored barium gelatin mass. Histologic sections were made of the AV node and His bundle in nine hearts. The blood supply to this region was traced radiographically, photographically and histologically. X‐rays of the upper ventricular septum were taken before and after coronary injection to demonstrate an os cordis. The sinus node is always supplied by a branch of the right coronary artery. The crux of the heart, and subsequently the AV node, is always supplied by the circumflex artery. The unbranched His bundle, unusually long in sheep, receives a dual blood supply from both the anterior septal branches and the AV node artery. The proximal part of the left and right bundle branches is supplied by the anterior septal branches in the majority of hearts. Intercoronary anastomoses are present in the majority of hearts, particularly in the upper ventricular septum. An os cordis, deep in the atrial septum and directly adjacent to the AV node, was found in all 25 hearts. Occasionally, a second bone was found in the anterior part of the left atrioventricular ring.