The heart is the most important muscle in the human body. Without the heart, a person cannot live. How does it work?
To understand how the heart works, we must first understand a little anatomy of the human heart. The human heart is about the size of its owner’s fist and is located in what is called the thoracic cavity. The heart acts as a pump to circulate the blood. The human heart has four chambers. The two upper chambers are known as the atria and the
two lower chambers are known as the ventricles. The atria contract at the same time. When the atria contract, blood is forced into the heart’s lower chambers which are the ventricles. Both ventricles receive blood from their respective atria. For example, the left ventricle receives blood only from the left atrium and vice versa. The ventricles them contract simultaneously to pump blood out of the heart.
Blood flow in the heart has a definite pathway. Blood enters the right atrium, passes on to the right ventricle, moves to the lungs, then returns through the left atrium and on to the left ventricle, which pumps the blood out to the body.
Blood comes to the right atria in what is known as the vena cavae. These are two large veins that return blood from the body to the heart. The right atrium receives this blood and delivers it to the right ventricle, through the bicuspid valve. When the right ventricle contracts, it pumps deoxygenated blood out of the lungs via the pulmonary arteries.
The blood then travels to the lungs to become oxygenated. After the blood is oxygenated, it returns to the heart via the pulmonary veins to the left atrium. When the left atrium contracts, it sends blood to the left ventricle through the tricuspid valve (also called the mitral valve). The left ventricle then contracts and the blood is pumped into the aorta.
The aorta is the body’s largest artery. This is important because the aorta must then distribute blood to the entire body. Between each atrium and ventricle is a one-way valve preventing backflow of blood; they have names as mentioned above. These valves keep the blood moving in the correct direction.
The contractions of the heart are involuntary, meaning you don’t have to think about contracting your heart. The heart has its own natural pacemaker and a system of specialized tissues that conduct electrical impulses that stimulate the heart to beat. The heart’s natural pacemaker is called the sinoatrial (SA) node and is in the top part of the atria.
The electrical pulse travels down, making the atria contract, and then is recollected in the atrioventricular (AV) node. The AV node then fires, sending a pulse down the left and right bundles of His, then into the Purkinje fibers, which cause the ventricles to contract.
The heart is a very efficient pump. When the average adult is at rest, the heart pumps ten pints of blood each minute. When the body is active, this number is increasing. In an average lifetime, the heart is required to beat over 2.5 billion times–38 million times a day, doing the same amount of work as a machine lifting a one-ton weight to a height of 41 feet each day. The heart accomplishes this amazing feat without interruption.
The heart is susceptible to many diseases. The most common disease of the heart is Coronary Artery Disease (CAD). Most Americans have cholesterol plaques lining and narrowing the inside of their arteries, which is known as artherosclerosis; when this happens in the arteries which supply blood to the heart, it is called CAD.
These plaques reduce the amount of oxygen-carrying blood that can flow in a given period of time. Atherosclerosis does not provide advanced symptoms. If the narrowing reaches an advanced stage, it may result in a sudden coronary event such as cardiac arrest.
Cardiac arrest means that the heart has stopped beating. How do you prevent this? Regular physical exams can help monitor blood pressure and cholesterol levels. Diet, exercising, and quitting smoking also help.
Congestive heart failure (CHF) is another common disease of the heart. This occurs when the pumping action of the heart becomes inefficient. The inefficiency could be caused by the muscle being weakened, by disease, mechanical fault in the valves that control the flow of blood, the heart having too work to hard because of high blood pressure, or it has to pump an overload of blood.
Heart failure does not mean that your heart stops beating, it means that it is not working efficiently. Depending on how badly the heart is affected, symptoms could include shortness of breath, chest pain, and swollen ankles. Untreated heart failure imposes a strain on your entire system that can be fatal. There are diseases that are also related to the electrical impulses of the heart, such as ectopic heartbeats.
Ectopic heartbeats are early beats in an otherwise steady beat. This can mean your heart skipping a beat or adding an extra beat. Other times the SA node(which is the pacemaker) of the heart can stop working or work very poorly. In these such cases, a person may be required to have a pacemaker(an electrical device) implanted in their heart.
Ultimately, the most-feared heart disease is the “heart attack,” or, as health care professionals call it, an acute myocardial infarction (AMI). This is where the coronary arteries have narrowed so much that part of the heart muscle dies. This is usually due to CAD but can be caused by blood clots or drug use (especially cocaine). Depending on how much damage is done, a person may return to an almost normal life, die, or anything in between.
The heart is a complex organ, and one of the two most important organs in your body (the other being the brain). Regular physicals and talking to your doctor can help you take care of it for your lifetime.