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2013-6-21 17:15 上传
作者: jxw306011 时间: 2013-6-24 09:51
虽然听不懂 不过很形象
作者: stw0509 时间: 2013-7-15 06:41
High blood pressure or hypertension
High blood pressure or hypertension is a common condition in which the force of blood on the walls of the your arteries is often too high
arteries are the blood vessels that carry blood away from your heart to supply your tissues with oxgen and nurtrients.
In your heart , two chambers called ventricles contract with each heart beat to push blood to your lungs and through your arteries to your body, as blood flow through them ,three main factors affect the pressure on your artery walls
The first is cardiac output or the amount of blood your ventricles push out of your heart each
Minute, your blood pressure goes up as cardiac output increases
The second factor affecting your blood pressure is blood volume or the total amount of blood in your body. blood pressure also goes up as blood volume increases.
The third factor that affect your blood pressure is resistance which is anything working against the blood flow through your arteries. several factors contribute to resistance, one resistance factor is the flexibility of your artery wall. Healthy arteries expand with each heart beat to help reduce blood pressure on the wall. Another resistance factor is the diameter of your arteries ,your body is able to increase the diameter of your arteries to lower your blood pressure, or reduce the diameter to raise your blood pressure, a third resistance factor is blood viscosity or thickness. In your blood , more particles such as proteins and fat increase viscosity, if your blood is thicker ,your blood pressure goes up as your heart works harder to push through your arteries.
Your blood pressure can be measured with a device called sphygmomanometer or blood pressure cuff .when your heart beats, the pressure of blood on the walls of your arteries is called systolic pressure. when your heart relaxes between beats, pressure on the artery wall is called diastolic pressure. While your blood pressure may change throughout the day , it should normally be less than 120mmhg for systolic pressure and less than 80mmhg for diastolic pressure. If your systolic pressure frequently stays above 140mmhg or your diastolic pressure frequently stays above 90mmhg, you have high blood pressure.
Overtime, high blood pressure will damage the walls of your arteries. Your artery wall may become weak, and form an enlargement called aneurysm or the wall may burst, and bleed into the surrounding tissue, small tears in your artery wall may attract certain substances in your blood such as cholesterol fat and calcium to form build-up called a plaque, blood flow through your artery decreases as the plaque enlarges, blood cells can stick to the plaque and form solid clumps called clots, further reducing or completely blocking your blood flow, damage to your arteries raises your blood pressure even more by making your heart beat more forcefully , artery damage and reduce blood flow lead to conditions such as a stroke , heart attack , or kidney diseases .
In most cases , the cause of high blood pressure or hypertension is unknown , this type of high blood pressure is called primary or essential hypertension,
Treatment for essential hypertension includes lifestyle changes such as eating a healthy diet, if you are insensitive to the sodium and salt , your doctor may recommend limiting your intake of salt and highly processed foods .sodium may cause your body to retain water, which increase both your blood volume and your blood pressure. Other lifestyle changes that can reduce blood pressure include avoiding excessive alcohol intake, getting regular exercise, losing weight if you are overweight, and quiting smoking, your doctor may also recommend medications that act on your kidneys, blood vessels or heart to help reduce your blood pressure , diuretics commonly called water pills cause your kidneys to move more salt and water from your blood into your urine which reduces your blood volume and pressure. Beta blockers reduces the work load on your heart by decreasing both the heart beat of your heart and the strength of your hearts contractions , several types of drugs act directly or indirectly to reduce your blood pressure by relaxing your blood vessels which increases their diammer , these drugs include ACE inhibitors , Angiotensin ii receptor blockers , calcium channel blockers and direct-acting vasodilators.
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