This document summarizes key aspects of venous circulation of the heart, the coronary sinus, fetal circulation, and nerve supply of the heart. It notes that around 60% of venous blood from the heart drains into the right atrium via the coronary sinus, while the rest drains into heart chambers via other veins. It describes the anatomy and tributaries of the coronary sinus. It then briefly outlines fetal circulation via the umbilical cord, ductus venosus, foramen ovale and ductus arteriosus. Finally, it summarizes the parasympathetic and sympathetic nerve supply to the heart via the cardiac plexuses.