DNA replication is the process by which a double-stranded DNA molecule is copied to produce two identical DNA molecules.
The heart pumps oxygenated blood to the body and deoxygenated blood to the lungs. In the human heart there is one atrium and one ventricle for each circulation, and with both a systemic and a pulmonary circulation there are four chambers in total: left atrium, left ventricle, right atrium and right ventricle.
Branches of these arteries supply the heart with oxygen and nutrients whilst the cardiac veins drain the venous blood into the coronary sinus which empties into the right atrium. Systemic circulation takes blood to the whole body and returns to the heart through the inferior and superior vena cava.