To understand why lowering high blood pressure is so important in preventing heart and blood vessel
diseases, it is important to know something about the basic physiology involved. As noted in Chapter 1, the
blood circulates through some 60,000 miles of blood vessels. (See color atlas, #4.) With each heartbeat, 2
or 3 ounces of freshly oxygenated blood are forced out of the heart’s main pumping chamber, the left
ventricle, into the aorta, the body's largest artery.