["In humans, the heart is approximately the size of a closed fist and is located between the lungs, in the middle compartment of the chest, called the mediastinum. [4]", "Heart, organ that serves as a pump to circulate the blood. It may be as simple as a straight tube, as in spiders and annelid worms, or as complex as the four-chambered double pump that is the", "Electrical impulses make your heart beat, moving blood through these chambers. Your brain and nervous system direct your heart’s function. What is the function of the heart? Your heart’s", "Learn about the anatomy of the heart and how its chambers, valves, and vessels work together to maintain effective blood circulation throughout the body to sustain life.", "This image shows the four chambers of the heart and the direction that blood flows through the heart. Oxygen-poor blood, shown in blue-purple, flows into the heart and is pumped out to", "Learn more about the American Heart Association's efforts to reduce death caused by heart disease and stroke. Also learn about cardiovascular conditions, ECC and CPR, donating, heart disease", "The heart consists of four chambers – two atria and two ventricles: Blood returning to the heart enters the atria, and is then pumped into the ventricles. From the left ventricle, blood passes into"]