Fig. (8).

(A)Dissection of the left lateral wall of the left atrium to show the myofiber arrangement in the subepicardium of the lateral ridge (LR). Note the vein of Marshall in relationship with LS, left superior; LI, left inferior pulmonary veins. CS, coronary sinus; LAA, left atrial appendage. (B) Sagittal section showing the oblique vein of Marshall and the arrows indicating ganglion and nerve bundles in the vicinity of the vein. (C) Histological section through the left atrioventricular junction shows the coronary sinus (CS) and circumflex artery (LCx) . The CS is surrounded by a sleeve of muscle. There is muscular continuity (arrows) between the sleeve and posterior left atrial wall. MV, mitral valve. (D) Histological cross-sections (Masson trichrome stain) through the coronary sinus (CS) demonstrate the coronary sinus-left atrium muscle connection (asterisks) at the distal end of the coronary sinus. The rest of the myocardial sleeve of the CS is separated from the left atrium wall by epicardial fat. LCx, left circumflex artery; Thv, Thebesian valve; VV, valve of Vieussens.