The 16th and 17th centuries also witnessed significant advances in the understanding of the circulatory system, as the purpose of valves in veins was identified, the left-to-right ventricle flow of blood through the circulatory system was described, and the hepatic veins were identified as a separate portion of the circulatory system.
32.
There are four variants : Supracardiac ( 50 % ) : blood drains to one of the innominate veins ( brachiocephalic veins ) or the superior vena cava; Cardiac ( 20 % ), where blood drains into coronary sinus or directly into right atrium; Infradiaphragmatic ( 20 % ), where blood drains into portal or hepatic veins; and a mixed ( 10 % ) variant.
