Preventing and Reversing Heart Disease For Dummies. James M. Rippe
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СКАЧАТЬ tissues, causing the heart to contract. When any of these electrical structures becomes diseased or disordered, arrhythmias (ay-rith-mee-uhz), or heart rhythm disturbances, occur.

      ✔ The pericardium: The entire heart is positioned in a thin sac called the pericardium (peri = around and cardium = heart; pronounced per-ry-car-dee-um). Fluid within the sac lubricates the constantly moving surfaces. Inflammation of the pericardium from an infection or other cause causes pericarditis. Build-up of excess fluid inside the pericardium can cause problems with how the heart functions, a condition called cardiac tamponade.

      Illustration by Kathryn Born

      Figure 2-1: A typical healthy heart.

      Illustration by Kathryn Born

      Figure 2-2: The interior of a normal heart.

       Connecting every cell in your body: The cardiovascular system

      A pump is useless without the rest of the plumbing, which in your body is called the cardiovascular system. Here’s a quick look at how it all fits together and functions.

      ✔ The lungs: The lungs are composed of an intricate series of air sacs surrounded by a complex, highly branching network of blood vessels. Their sole purpose is to receive the deoxygenated blood from the heart, fill the red corpuscles full of fresh oxygen, and send them back to the heart for delivery to the body. The red blood cells give off waste products such as carbon dioxide at the same time they take on oxygen; the lungs then expel the carbon dioxide. This low-pressure system facilitates the rapid flow and reoxygenation of enormous amounts of blood.

      ✔ The arteries: As oxygenated blood returns to the left side of the heart, it is pumped out to the body through the aorta, the main artery of the body, and into the rest of the arterial system to feed the entire body with oxygenated blood. Although the heart exerts enough force to push oxygenated blood throughout the body, the arteries also have muscular walls that help push the blood along. The force exerted against resistance of the artery walls creates a high-pressure system that is very elastic to allow the arteries to expand or contract to meet the needs of various organs and muscles. Your blood pressure reading results from measuring the pressure in these arteries when contracting and at rest. (Read more about high blood pressure in Chapter 8.)

      ✔ The capillaries: The arterial system divides and redivides into a system of ever smaller branches to distribute nourishing blood to each individual cell, ultimately ending up in a network of microscopic vessels called capillaries, which deliver oxygenated blood to the working cells of every organ and muscle in the body.

      ✔ The veins: After oxygen leaves the capillary system, the deoxygenated blood and waste products from the cells are carried back through the body in the veins. The veins ultimately come together in two very large veins, called the inferior vena cava (vee-nuh cay-vuh) and the superior vena cava. The inferior vena cava drains blood from the lower part of the body and superior vena cava drains blood from the upper part of the body. These veins discharge blood into the right atrium of the heart to be pumped into the right ventricle and out to the lungs again to start the whole process over again.

      ✔ The blood: Although blood is not considered part of the cardiovascular system, circulating blood to every cell of the body is the reason the cardiovascular system exists. This red fluid transports oxygen and fuel to the cells and removes waste products. It’s also the delivery vehicle for many specialized cells and biochemicals, including those that contribute to the development of heart disease.

       Keeping the beat: How the nervous system controls heart rate

      

In addition to its internal electrical system, the heart has profound linkages to the nervous system that provide additional control of the heart rate. Two main branches of the involuntary nervous system interact with the heart – the sympathetic nervous system and the parasympathetic nervous system. In simple terms, the sympathetic nervous system helps the heart speed up, and the parasympathetic nervous system helps the heart slow down. They act through direct nerve links to the heart and through the release of chemical substances that reach the heart through the bloodstream.

       Understanding How Heart Disease Begins and Develops

      The human cardiovascular system is wondrously complex. If every element is in balance and working as it should, a state called homeostasis, then the whole system, including the heart and blood vessels, would remain healthy. Unfortunately, multiple factors related to your biology and lifestyle can tip the system out of balance and trigger the development of heart disease. The earliest changes typically start in childhood or adolescence and then silently progress for years before producing changes that can be seen in diagnostic tests or symptoms that you experience. The most common type of cardiovascular disease is atherosclerosis.

       Defining atherosclerosis – the most common form of cardiovascular disease

      Atherosclerosis results from the gradual buildup of fatty deposits called plaque, or lesions, in the interior walls of large and medium-sized arteries. The disease process starts with small changes in the artery wall and takes years to develop to a point where the narrowing arteries may produce symptoms or negatively affect your health.

      Narrowing in the heart’s arteries leads to coronary heart disease (CHD), also called coronary artery disease (CAD). CHD gradually starves the heart muscle of the high level of oxygenated blood that it needs to function properly. A lack of adequate blood supply to the heart typically produces symptoms that range from angina and unstable angina (see “Recognizing angina, or chest pain” and “Defining Unstable Angina” later in this chapter) to heart attack or sudden death. Narrowing of the carotid arteries that carry blood to the brain increases your risk of stroke. Narrowed arteries in your legs or arms results in peripheral artery disease (PAD).

      The term atherosclerosis comes from two Greek words – athero (paste, gruel) and sclerosis (hardness) – that may give you a graphic image of hardened sludge. Not a pretty picture, is it? But it’s an apt image for these deposits of cholesterol, other fats, cellular wastes, platelets, calcium, and other substances. These deposits typically start with fatty streaks and grow to large bumps that distort the artery and block its interior where the blood must flow. Some plaques are stable and others are unstable or vulnerable to cracking or rupturing, which often leads to an artery-blocking blood clot and subsequent heart attack. The sections that follow profile that development process.

      

During the last 15 to 20 years, evidence from extensive population studies and clinical research has increased doctors’ understanding of the many factors and pathways that contribute to the beginnings and progress of atherosclerosis. The next sections provide an overview of medical science’s best understanding right now; however, you need to remember that new studies continually add to the knowledge of this complex, multifaceted disease.

       Triggering the precursors of atherosclerosis

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