The heart is the pump of life that never takes a break. Without the heart, the lungs would only absorb oxygen into themselves, the brain would be lifeless, and muscles would lose function. Essentially, the body would die. A healthy heart requires all its parts to be working. Otherwise, complications can arise. The heart is arguably the most important organ in the body to sustain life because of its complex anatomy, efficient oxygen delivery, and independent electrical system. The heart is a hollow organ that pumps blood throughout the body. It is located in an area called the mediastinum, slightly to the left of the sternum, or breastbone. A heart weighs anywhere from seven to fifteen ounces and is approximately the size of its owner’s fist. The medical term for the heart is the myocardium, and it is surrounded by a protective sac called the pericardium. The heart has four chambers, consisting of the left and right atria (singular atrium, Latin for entrance), and left and right ventricles, directly below the atria. In between each of these chambers are valves that, with the help of the electrical system, open and close to regulate blood flow in the heart. These valves are the tricuspid valve, in between the right atrium and right ventricle; the pulmonary valve, in between the right ventricle and the pulmonary arteries; the mitral valve, in between the left atrium and left ventricle; and the aortic valve, in between the left ventricle, and the aorta. Without these valves, a regular rhythm would be impossible, because blood would be unable to stop itself; much like a waterfall has no regular rhythm. Without a regular rhythm, the heart could not function, which in turn would lead to death, because all body systems require oxygenated blood. For example, the brain needs oxygenated blood, in order to control breathing, blood pressure, heart rate, and thought. Oxygen is vital to sustain life, and the heart makes sure oxygen gets to the rest of the body. The right atrium receives oxygen-poor blood from the largest vein in the body, called the vena cava. (A vein is any blood vessel in your body that carries blood to the heart. An artery is any blood vessel that carries blood away from the heart.) Once blood is in the right atrium, the tricuspid valve opens, and blood moves into the right ventricle, which pumps blood through the pulmonary valve to the pulmonary arteries. Here, oxygen poor blood is carried to the lungs where it is oxygenated in a process called diffusion (molecules move from an area of high concentration, to an area of low concentration). After diffusion, the pulmonary veins carry oxygen-rich blood to the left atrium. Oxygen rich blood is then forced through the mitral valve to the left ventricle. The left ventricle then forces the oxygen rich blood up through the aortic valve to the aorta which carries this blood to the rest of the body. Efficient blood flow would be impossible in the human body without this complex arrangement. The intricate activities humans do like run, swim, and process intelligent thought would all be impossible without this arrangement. For example, if there were no pulmonary arteries or veins, oxygen would simply enter and exit the lungs. Diffusion would not occur, and oxygenated blood could not return to the heart to be pumped throughout the body. All organs, including the brain would lose function without the heart. There are some organs humans can live without. The heart is not one of these organs. Besides the brain, the only organ in the body with its own electrical system is the heart. Each heartbeat is dependent on this electrical system. The heart has its own pacemaker called the sinoatrial node or SA node, which sends an electrical impulse that causes the atria to contract. This phase of the heartbeat is called diastole, when the ventricles are at rest. During diastole, blood is pushed from the atria through the tricuspid and mitral valves into the left and right ventricles. The next phase is called systole. During this phase, the electricity passes to the atrioventricular node or AV node. This node causes the tricuspid and mitral valves to be shut, preventing any back-flow of blood into the atria, and the pulmonary and aortic valves are pushed open. Blood from the right ventricle is then sent to the lungs to be oxygenated, while the left ventricle sends blood to the rest of the body. Once the ventricles are empty, the mitral and tricuspid valves are opened again, causing the whole process to be repeated again. Physicians call asystole a lack of electric activity in the heart. Unless the heart is revived, asystole is synonymous with death. Without the electrical system of the heart, the heart would cease to have rhythm, eventually leading to death. This is further proof the heart is one of the most important organs to sustain life functions. The heart’s complex anatomy, oxygen delivery, and electrical system allow all life functions to continue. The anatomy of the heart allows oxygen to be delivered to various body systems properly. The heart efficiently delivers oxygenated blood to various body systems. The electrical system of the heart organizes the pumping of blood throughout the body. Without the heart, oxygen would not be available to the body, and life would cease.