Which of the following does not directly drain into right atrium-

Ans. is 'a' i.e., Great cardiac vein o Great cardiac vein does not directly drains into right atrium. It drains into coronary sinus, which in turn drains into right atrium.Veinous drainage of heart1. Coronary sinus: Opens into right atrium and has following tributries : (i) Great cardiac vein, (ii) Middle cardiac vein, (iii) Posterior vein of left ventricule, (iv) Small cardiac vein, (v) Oblique vein of left atrium and (vi) Sometimes right marginal vein.2 Anterior cardiac vein : Opens into right atrium.3. Venae cardis minimi (thebasian veins) : Open into right atrium.4. Right marginal vein : More often opens into right atrium but sometimes into coronary sinus.