HOW THE HEART WORKS

Evening Star, Issue 18532, 15 January 1924, Page 6

HOW THE HEART WORKS

MEANING OF VALVULAR DISEASE. To understand valvular disease of the heart it is necessary to follow the coarse of the blood as it circulates to, from, and through the heart (says an English' writer). Blood is either venous or arterial. Venour blood is that which has served its purpose in the body. _ In the: first instance, it has been sent into the : body by the heart as arterial blood. In : its course through the body the different | organs and structures take nourishment from the arterial blood, and throw into it waste products. The blood which entered the organs as bright red arterial blood leaves them as dark, purple venous blood, laden with impurities. The venous blood ascends to the heart along the veins, which unite to form one big vein, the vena cava. The vena cava pours the venous blood into the right auricle of the heart. The heart is divided unto four chambers—on each side in an auricle and ventricle; the chambers of each side are separated by a muscular division which forms their inner wall. There is a right auricle and a left auricle; a right ventricle and a left ventricle. At every heart beat the auricles and ventricles oi the two sides contract together. The right side of the heart deals with venous, blood; the left side propels arterial blood. The venous blood coming from the body fills the right auricle, which then contracts and squeezes the blood into the right ventricle. The muscular contraction started in the auricle extends to the right ventricle, whose duty is to drive the • blood into and through the lungs. In the lungs the blood rids itself of carbonic acid gas, and takes up oxygen from the breathed air. It loses its dark purple color and becomes bright red arterial blood, fit for the service of the body and its organs. From the lungs the blood goes to the left side of _ the heart. Entering by the left auricle, it is propelled into the left ventricle, which with one powerful contraction sends it round the body, to reappear as venous blood to be again sent through the lungs. With one and the same beat the heart maintains two separate circulations, one through the lungs, the other round the body. The heart is, in fact, a double pump. Both sides of the heart work together, one side maintaining the circulation through the lungs, the other driving the arterial blood through the body. The right side of the heart has to overcome the resistance to the passage of the blood through the lungs, the_ left side to overpower the greater resistance offered by the body. There is a constant back pressure on the blood. If it were not for the valves this back pressure would force the blood back into the heart. As soon as the blood has poured out of the heart this back pressure comes into play, and closes the valves. As the blood cannot pass through the closed valves, it must continue to flow into tire vessels.