The cardiovascular system comprises the heart and blood vessels which carries nutrients and oxygen to the tissues of the body and removes carbon dioxide and other wastes from them. The cardiovascular system includes the pulmonary circulation, the systemic circulation, and the coronary circulation. The pulmonary circulation is part of the cardiovascular system which transports oxygen-depleted blood away from the heart, to the lungs, and returns oxygenated blood back to the heart. The systemic circulation is part of the cardiovascular system which transports oxygenated blood away from the heart, to the rest of the body, and returns oxygen-depleted blood back to the heart. Coronary circulation is another part of the cardiovascular system which refers to the movement of blood through the tissues of the heart. The coronary arteries refer to vessels that deliver oxygen-rich blood to the myocardium, while the coronary veins refer to vessels that remove the deoxygenated blood from the heart muscle. The coronary arteries are classified as "end circulation", since they represent the only source of blood supply to the myocardium: there is very little redundant blood supply, which is why blockage of these vessels can be so critical. Cardiovascular diseases (CVD) refer to the class of diseases that involve the heart and blood vessels (arteries and veins), including atherosclerosis, cardiac arrhythmias, cardiomyopathy, heart failure, hypertension, coronary diseases, coagulative disorders, and more. Most countries face high and increasing rates of cardiovascular disease. Take the United States for example; almost 1 million Americans die of cardiovascular diseases each year, which adds up to 42% of all deaths. Heart disease doesn't just kill the elderly -- it is the leading cause of death for all Americans age 35 and older. Heart disease accounts for over one million deaths each year; in 160,000 of those deaths the individuals were 35 to 64 years old.