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Disorders of the circulatory system include any injury or disease that damages the heart, the blood, or the blood vessels. The three most important circulatory diseases are hypertension, arteriosclerosis, and atherosclerosis.
Hypertension, or elevated blood pressure, develops when the body’s blood vessels narrow, causing the heart to pump harder than normal to push blood through the narrowed openings. Hypertension that remains untreated may cause heart enlargement and thickening of the heart muscle. Eventually the heart needs more oxygen to function, which can lead to heart failure, brain stroke, or kidney impairment. Some cases of hypertension can be treated by lifestyle changes such as a low-salt diet, maintenance of ideal weight, aerobic exercise, and a diet rich in fruits, vegetables, plant fiber, and the mineral potassium. If blood pressure remains high despite these lifestyle adjustments, medications may be effective in lowering the pressure by relaxing blood vessels and reducing the output of blood.
In arteriosclerosis, commonly known as hardening of the arteries, the walls of the arteries thicken, harden, and lose their elasticity. The heart must work harder than normal to deliver blood, and in advanced cases, it becomes impossible for the heart to supply sufficient blood to all parts of the body. Nobody knows what causes arteriosclerosis, but heredity, obesity, smoking, and a high-fat diet all appear to play roles.
Atherosclerosis, a form of arteriosclerosis, is the reduction in blood flow through the arteries caused by greasy deposits called plaque that form on the insides of arteries and partially restrict the flow of blood. Plaque deposits are associated with high concentrations of cholesterol in the blood. Blood flow is often further reduced by the formation of blood clots (see Thrombosis), which are most likely to form where the artery walls have been roughened by plaque. These blood clots can also break free and travel through the circulatory system until they become lodged somewhere else and reduce blood flow there (see Embolism). Reduction in blood flow can cause organ damage. When brain arteries become blocked and brain function is impaired, the result is a stroke. A heart attack occurs when a coronary artery becomes blocked and heart muscle is destroyed.
Risk factors that contribute to atherosclerosis include physical inactivity, smoking, a diet high in fat, high blood pressure, and diabetes. Some cases of atherosclerosis can be corrected with healthy lifestyle changes, aspirin to reduce blood clotting, or drugs to lower the blood cholesterol concentration. For more serious cases, surgery to dilate narrowed blood vessels with a balloon, known as angioplasty, or to remove plaque with a high-speed cutting drill, known as atherectomy, may be effective. Surgical bypass, in which spare arteries are used to construct a new path for blood flow, is also an option.
HISTORY OF HOSPITALS:
Today the United States is home to 6,021 hospitals that contain over 1 million hospital beds. U.S.hospitals annually admit some 34 million patients who are assigned a bed and receive medical or surgical treatment as inpatients. Hospitals also provide outpatient treatment in clinics or other walk-in, or ambulatory, settings for an additional 483 million patients every year.
Hospitals in the United States are classified by the services they provide (general or specialized), the length of stay they offer patients (short stay or long-term care), and by their ownership (not-for-profit, proprietary, or government owned). Although most U.S. hospitals are classified as not-for-profit, any one hospital will fall into several of the above categories. For example, Methodist Hospital in Houston, Texas, with more than 300,000 sq m (3 million sq ft) of space, is one of the largest short-stay, not-for-profit, general hospitals in the country.
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HISTORY OF HOSPITALS
