The heart distributes fresh oxygen to all parts of the body, in fact it has everything to do with circulation. Without it beating there would be no blood circulating, and without this there would be no live activity. Or, if we are more mechanically minded, we also may say our heart is the engine of our body. Why not then compare this live motor created out of muscle to an engine. To do this of course we will need to compare our bodies to a vehicle. This will be an excellent way of imagining our heart's role in the circulatory system since both needs supplies of energy to get from one place to another. Your heart is the engine and when it is not working right it is unable to push much needed fuel to where it can create energy for motion. Its powerful thrust of oxygenated blood out the left ventricle into the aorta for delivery to all parts of body is necessary for life.
Unlike an automobile, however, the heart is never turned off except when it is in a garage for an extensive fix. That sentence interpreted means when extensive heart surgery is being done and the dedicated and knowledgeable cardiac surgeon has suspended its function for the duration of the surgery. Not being a heart surgeon, or a doctor or even a mechanic I will leave off comparisons. You knew that the heart was the body's motor, anyway, didn't you?
Since the circulation is in a circular motion with the aorta carrying the rushing blood to where it is needed by way of smaller arteries and arterioles and when meeting up with venules, small veins, where it begins it trek back toward the heart and to the pulmonary circulation where it is restocked with oxygen by the lungs and then the journey begins again.
The cardiopulmonary system is a vast network of arteries and veins that work in unison and in harmony toward the purpose of maintaining the body at a balanced state. One way valves keep the blood flowing one way. Anything that upsets this balance will of course cause some disturbances in the heart and in the overall system. The organs of the body have their own circulatory needs as well. These are likewise supplied by the cardiopulmonary system.
The four chambers of the heart are designed as out-flowing and in-flowing or receiving and sending. Valves connecting the various chambers will not allow for blood mingling between the two. Pulmonary valves control the flow of blood from the right ventricle into the pulmonary arteries. They carry blood to the lungs; the mitral valve allows fresh oxygenated blood from the lungs to pass from the left atrium into the left ventricle where it begins its journey through the body. The aortic valve regulates the flow of blood from the left ventricle into the aorta. The tricuspid valve is between the right atrium and the right ventricle.
The heartbeat itself is the engine roar. When the little button, the sinotorial node gets pushed an electrical charge is started that courses from the SA node causing the atrium to contract then through the AV node to the muscles of the ventricles causing them to contract. The sound heard through a stethoscope is the heart beat.
The heart itself is served by two coronary arteries that branch, one to the left side of the heart, the other to the right. Located between the lungs and behind the sternum slightly to the left, the heart is enveloped into a sac like structure called the pericardium. It is composed of two layers of membranous sheaths. The outer sheath has a network of arterioles and venules that attach to the large blood vessels. The inside layer is attached to the heart muscles. Fluid separates and cushions the two layers.
The heart is not a dangling organ. The outside of the pericardium is attached by ligaments to the spinal cord and to the diaphragm. So, all in all, I would say the heart is a much more intricately designed machine than the finest automobile. Yet, as I say that pictures of the car industry with its vast troubles come to mind that is not unlike the trouble humanity has with its heart. Both have been ravished with too much of this and too much of that. And both are in the process of change. Too much exhaust from fast driving and wrong fuel is not good for either. For more information check out the American Heart Association or the automobile industry. Both will be helpful.