“…Drainage of the heart is carried out by the great cardiac vein, the middle cardiac vein, the right cardiac veins and the smallest cardiac veins (Hegazi, 1958; Nickel et al, 1981; Yadm and Gad, 1992; Yadm, 1993; Aksoy et al, 2001). The great cardiac vein and the middle cardiac vein terminate at the coronary sinus which is constituted by the continuation of the great cardiac vein (Ghoshal, 1975; Esperenca et al, 1981; Nickel et al, 1981; Yadm and Gad, 1992; Piffer et al, 1994; Maric et al, 1996; Aksoy et al, 2001). The coronary sinus opens into the right atrium ventral to the opening of the caudal vena cava, and it has a semicircular valve (Crouch and Lackey, 1969; Field and Taylor, 1969; Getty, 1975; Ghoshal et al, 1981; Yadm, 1993; Aksoy et al, 2001).…”