The main components of the heart are the two atria, two ventricles and four valves, the National Heart, Lung, and Blood Institute states. The atria, or upper heart chambers, receive blood, while the ventricles, or lower chambers, circulate blood out of the heart. The mitral and tricuspid valves regulate blood flow from the atria to the ventricles. The pulmonary valve controls flow between the right ventricle and pulmonary artery, and the left ventricle feeds blood through the aortic valve.
The heart functions like a pump, moving blood through its mostly hollow interior, according to Healthline. The heart wall consists of three layers: the epicardium, myocardium and endocardium. The epicardium is the thin outer membrane, and the endocardium is the innermost layer made up of smooth tissue. The myocardium is a middle layer of muscle that repeatedly expands and contracts to enable the heart's pumping motion. The heart muscle has the capacity to circulate up to 2,000 gallons of blood through the body each day.
Several major blood vessels of the circulatory system connected to the heart help deliver blood and oxygen to the rest of the body, the National Heart, Lung, and Blood Institute notes. The superior and inferior vena cavae, located along the right side of the heart, are the body's largest veins. Blood that has already distributed its oxygen stores flows through the vena cavae to the right atrium. The coronary arteries, located on the heart's surface, receive oxygen-rich blood from the left ventricle and supply it to the heart.