Your heart has four hollow chambers. The atria, which are smaller and less muscular, are at the top, and the ventricles are at the bottom. The right atrium and ventricle pump oxygen-depleted blood to the lungs, and the left atrium and ventricle pump newly oxygenated blood to the body.
There are four valves within your heart: the mitral, tricuspid, aortic and pulmonary valves. The mitral valve and tricuspid valve lie between the atria and the ventricles. The aortic valve and pulmonary valve lie between the ventricles and the major blood vessels leaving the heart. As blood flows from each chamber of the heart, it passes through a valve. Your heart valves ensure that blood flows in only one direction through your heart.
Blood doesn't flow steadily and smoothly through your arteries, it surges each time the heart beats. That surge is what you feel as your pulse: the difference between the pressure exerted on the arterial walls when the heart beats and when it rests between beats. But although blood surges through the vessels, there is pressure on their interior walls all the time: your blood pressure.
Blood pressure is often stated as two numbers, systole and diastole. Systolic pressure is the first or top number, and it represents the pressure when the heart contracts. Diastolic pressure is the second or bottom number, and it represents the pressure when the heart rests between beats. Normal blood pressure for an adult is 120 mm Hg/80 mm Hg or less, while high blood pressure is considered to be 140 mm Hg/90 mm Hg or more. Hypertension is dangerous because it can lead to hardened arteries, or atherosclerosis, which decreases blood flow to the heart and other parts of the body. This can cause heart disease. Hypertension can also cause eye problems, including blindness, and lead to kidney disease and stroke. That's why it's so important to monitor your blood pressure, especially if you have high blood pressure.
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