The coronary sinus was investigated in 34 normal adult dogs, in order to verify its formation, tributaries, length and the valves, as well as the relationship of the venous walls to the epicardium and to the myocardium. The valve of the coronary sinus was observed in only 4 cases (1.7%). In 30 cases (98.3%) the ostium of the coronary sinus was lacking a valve. The valve of Vieussens double, was found at the level of the transition between the great cardiac vein and the coronary sinus, as well as others parietal venous valves. A comparison with the human pattern was made, particularly regarding the action of the valve of the coronary sinus and the formation of the sinus.

Summary: The authors admit that the conjunctive-muscular constitution of the walls of the superior venae cavae throughout the length of the intrapericardium segment and the debouchement in the right atrium, associated with the presence of a myocardium sheath can be made up of a functional device of sphincter form able to act on the control of the blood flow to the interior of the arterial chamber as well as stopping blood flow during the arterial systole. The fixation of the venous wall to the deep chamber of the serous pericardium, contributes to growth in resistance during the elevation of venous pressure, making possible the preservation of integrity of the superior venae cavae. The expansion of fasciculi of nodal fibers in the right wall of the superior venae cavae permits that the unlocked impulse in the S-A node also reaches the vascular wall contributing to the shortening and diminution in caliber of the vein.