<prompt> Anterior cardiac vein opens into -Right atriumCoronary sinusThebesian veinsMiddle cardiac vein  <response>: Ans. is a i.e., 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 cordis minimi thebasian veins: Open into right atrium.4. Right marginal vein: More often opens into right atrium but sometimes into coronary sinus. 