Blood Circulation. The heart and the blood vessels (arteries, veins, and capillaries) circulate blood through the body tissues. The heart is divided into two separate halves, each acting as a pump. The left side pumps oxygenated blood (bright red) through the arteries into the capillaries; nutrients and oxygen pass from the blood through the walls of the capillaries into the cells. At the same time waste products and CO2 enter the capillaries. From the capillaries the oxygen poor blood is carried through the veins to the right side of the heart and then into the lungs where it expels the CO2 and picks up oxygen. Blood in the veins is dark red because of its low oxygen content. Blood does not flow through the veins in spurts as it does through the arteries. The entire system of the heart, blood vessels, and lymphatics is called the circulatory system. (1) Heartbeat. The heart functions as a pump to circulate the blood continuously through the blood vessels to all parts of the body. It contracts, forcing the blood from its chambers; then it relaxes, permitting its chambers to refill with blood. The rhythmical cycle of contraction and relaxation is called the heartbeat. The normal heartbeat is from 60 to 80 beats per minute. (2) Pulse. The heartbeat causes a rhythmical expansion and contraction of the arteries as it forces blood through them. This cycle of expansion and contraction can be felt (monitored) at various points in the body and is called the pulse. The common points for checking the pulse are at the— • Side of the neck (carotid). • Groin (femoral). • Wrist (radial). • Ankle (posterior tibial). (a) Carotid pulse. To check the carotid pulse, feel for a pulse on the side of the casualty’s neck closest to you. This is done by placing the tips of your first two fingers beside his Adam’s apple (Figure 1-2).
Posted on: Sun, 09 Jun 2013 19:22:10 +0000
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