Machine that produces the electrocardiogram The method of recording and the interpretation of electrocardiograms electrode ee- LEK -trode S/ R/ -ode way, road electr- electricity A device for conducting electricity mediastinum ME -dee-ass- TI E -num S/ P/ R/ -um structure media- middle -stin- partition Area between the lungs containing the heart, aorta, venae cavae, esophagus, and trachea perfusion per- FYU -zhun S/ R/ -ion action perfus- to pour The act of forcing blood to flow through a lumen or a vascular bed phlebotomist phlebotomy fleh-BOT-oh-mi st fleh- BOT -oh-m e S/ R/C F R/ S/ -ist specialist in phleb/o- vein -tom- incise, cut -tomy surgical incision Person skilled in taking blood from veins Withdrawing blood from a vein through a needle or catheter sternum STIR -num Latin the chest Long, flat bone forming the center of the anterior wall of the chest thoracic cavity THOR -ass-ik KAV -ih-tee S/ R/ -ic pertaining to thorac- chest cavity, Latin hollow Space within the chest containing the lungs, heart, esophagus, trachea, aorta, venae
cavae, and pulmonary vessels Functions of the Heart (LO 6.4) In order to keep your body alive, your heart must work all the time, without stopping. Its three most important functions are to: 1. Pump blood. As your heart contracts, it generates pressure that moves your blood through your blood vessels. 2. Route blood. Your heart essentially has two pumps: one on the right side that sends blood through the pulmonary circulation of your lungs and back to the second pump on your left side, which sends blood through the systemic circulation of your body. Your heart valves make this one-way flow of blood possible. 3. Regulate blood supply. The changing metabolic needs of your tissues and organs—for example, when you exercise—are met by changes in the rate and force of your heart's contractions. Structure of the Heart (LO 6.4) The heart wall consists of three layers ( Figure 6.2 ) :
▲ FIGURE 6.2 Heart Wall. 1. Endocardium: Connective tissue lining the inside of your heart. 2. Myocardium: Cardiac muscle cells that contract to enable your heart to pump blood. 3. Epicardium: An outer single layer of cells overlying a thin layer of connective tissue. The pericardium is a double-layered connective tissue sac that surrounds and protects your heart. Blood Supply to Heart Muscle (LO 6.5) Because your heart beats continually and forcefully, it requires an abundant supply of oxygen and nutrients. To meet this need, your cardiac muscle has its own blood circulation called the coronary circulation ( Figure 6.3 ) . This system of arteries arises directly from the aorta.
▲ FIGURE 6.3 Coronary Arterial Circulation. If any of your coronary arteries become blocked, the blood supply to a part of your cardiac muscle is cut off (ischemia) and the cells supplied by that artery die (necrosis) within minutes.
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- Spring '14