Your heart, a muscular structure about the size of your fist, and a 60,000-mile network of blood vessels make up your cardiovascular system. The heart itself is the focal point because it performs the main function of the cardiovascular system: pumping blood to all the tissues of the body. The muscle responsible for pumping the blood is called the myocardium (myo means "muscle," cardia means "heart"). Although the myocardium is the driving force of the circulation, it could not function as a pump without all of the other components that combine with it to make up the cardiovascular system: the valves, the coronary vessels, the conduction (electrical) system, the arteries and veins throughout the body, and the pericardium (the sac around the heart).
Location of the Myocardium (Heart Muscle)
Your heart is located slightly to the left of the center of your chest, protected by the breastbone (sternum) in front, the spinal column in back, and the lungs on both sides.
The right side of your heart projects toward the front of the chest, and the left side is toward the back. In an adult the heart weighs about 3/4 pound.
Both sides of the heart atrium (a small upper receiving) and a ventricle (a large lower pumping chamber). The two sides of the heart are linked in a fig loop connected by the arteries and veins of the lungs and the art veins of the rest of the body.