Dissection of pericardium and heart in situ

Interatrial cleavage plane

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Image #118-1
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Legend Image
Dissection of pericardium and heart in situ
Interatrial cleavage plane
An incision has been made in the epicardium (6) bordering the right atrium. The superior vena cava and upper part of the right atrium have been reflected anteriorly and to the left to display the plane of cleavage between the myocardial layers of the right and left atria. In the upper part of the area of contact of the atria there is no interconnection of the two myocardial layers. In the lower part (9), which overlies the point of entrance of the lower right pulmonary vein into the left atrium, there is considerable interweaving of muscle fibers of the two atria. The proximity of this cleavage plane to the fossa ovalis can be readily visualized, although the fossa ovalis is partially obscured in this view.
1 . Azygos vein (divided)
2 . Right main bronchus
3 . Tracheobronchial lymph node
4 . Cardiac plexus
5 . Right pulmonary artery
6 . Incision in epicardium to display interatrial cleavage plane
7 . Myocardium of left atrium (overlying upper right pulmonary vein)
8 . Nerve filament of cardiac plexus
9 . Area of intermingling atrial muscle fasciculi
10 . Sino-atrial node
11 . Fossa ovalis
12 . Wall of right atrium
13 . Pericardium
14 . Right phrenic nerve
15 . Ascending aorta
16 . Superior vena cava (retracted)
17 . Left coronary artery
18 . Latex cast within left ventricle
19 . Interventricular septum
20 . Border of fossa ovalis
21 . Right ventricle
22 . Latex cast within inferior vena cava