The short trunk that recieves most of the cardiac veins carrying the blood from the myocardium and delivers it to the right atrium, with the sinoatrial connection occurring between the inferior vena cava and the atrioventricular orifice.
Comment:
[structure-note] "The sinus, before entering the auricle, is considerably dilated - nearly to the size of the end of the little finger. Its wall is partly muscular, and at its junction with the great coronary vein is somewhat constricted and furnished with a valve consisting of two unequal segments" xsd:string {source="WP"}