The sinoatrial node (4) has been exposed by removal of the epicardium near the junction of the superior vena cava and the right atrium. The atrioventricular node (16) has been exposed by the removal of endocardium and some atrial myocardium just above the entrance of the coronary sinus into the right atrium. The atrioventricular bundle has been dissected in its course into the membranous atrioventricular septum, and its right branch (15) has been uncovered by the removal of endocardium and a portion of the myocardium of the muscular interventricular septum. A segment of the septal cusp of the tricuspid valve has also been cut away.
Ascending aorta
Reflection of pericardium onto superior vena cava
Right coronary artery (cut off)
Sinoatrial node
Upper pointer: Interventricular septum (membranous part) Lower pointer: Right fibrous trigone (exposed by removal of atrial myocardium)
Border of fossa ovalis
Fossa ovalis
Myocardium of right atrium (left pointer indicates position of a delicate tendon which extends from the right fibrous trigone toward the border of fossa ovalis)
Upper pointer: Latex cast in coronary sinus Lower pointer: Valve of coronary sinus
Valve of inferior vena cava
Latex cast in inferior vena cava
Septal (medial) cusp of tricuspid valve
Pulmonary trunk
Valve of pulmonary trunk (pointer on left semilunar cusp)
Right crus atrioventricular bundle
Atrioventricular node (no distinct boundary found between node and myocardium inferior to it)