Pulse blood system blood distribution blood pressure

THE PULSE You have undoubtedly noted physicians-and perhaps you have done the same yourself-place a finger on the radial artery ,It the wrist to "take" the pulse. The pulse is caused by the impart of blood on the arteries as the heart beats. It provides useful information about the strength and regularity of blood flow. Generally, for a person in good health, the pulse may speed up from around 70 a minute to more than 120 after vigorous exercise, but then, within three minutes, should return to the original value. There may be some quite normal deviations from average beat, deviations too from the beat with vigorous exercise, and deviations from the average interval required for return to the pre-exercise rate. If you have any doubt in your own case, you should check with your physician.

BLOOD PRESSURE Blood pressure is the force exerted against the walls of arteries as blood flows through. With each contraction of the ventricles, which is called a systole, there is a spurt of blood and this increases blood pressure. During the art of the cycle when the ventricles are not contracting, called the diastole, the pressure decreases. Thus, there is always pressure of blood, highest during systole and called the systolic pressure, lowest during diastole and called diastolic pressure. These pressures can be readily measured with an instrument, the sphygmomanometer (see page 24). And, as the discussion under high blood pressure indicates (page 596), measurement of pressure is an important means of determining the health of the heart and circulatory system.

BLOOD DISTRIBUTION The circulation of blood-so often dismissed as "blood from the heart into the arteries, to the tissues, then back to the heart through the veins" -is, in the human body, a really intricate and marvelous process. For it is remarkably adaptable. When blood moves from the heart into the aorta, it is at a speed of about 15 inches a second. Almost immediately, distribution around the body begins through arteries branching off from the aorta. From the smallest arteries, even smaller vessels called arterioles branch out. From the arterioles, blood flows to the smallest of all vessels, the capillaries. The capillaries transport blood to individual cells; and through microscopic spaces in the capillary walls, oxygen and other supplies are diffused to the cells and, in return, waste materials move into the blood- stream. The capillaries connect with venules, tiny vessels of the venous return system, which run into veins. The veins carry the blood to the great venae cavae, large vessels which empty into the right atrium of the heart.