TABLE OF CONTENTS So far we have considered materials and devices which are in the main passively implanted in the body for relatively short periods. Now we must turn to another group of implants, such as: mechanical heart valves, as well as complex machinery, eg pacemakers, artificial hearts and other cardiac assist devices, cosmetic, and oral implants. Whilst both have to withstand the effects of rejection and the action of the body fluids, the former have also to operate mechanically over long periods of time.
We saw in Chapter 1 that the heart is essentially a pump, whose function is to deliver oxygen-rich blood to the arteries, and thence to the cells, so that they may receive the oxygen necessary for their survival. The blood flow is controlled by the heart valves, and Fig. 1.7 shows the arrangement of the valves within the heart itself Fig. 7.1 depicts a section through the heart showing the location of the four valves.
Once the blood has given up its oxygen, it enters the right atrium, which then contracts, forcing the blood down through the tricuspid valve into the right ventricle. This chamber then contracts, pushing the blood through the pulmonary valve to receive its supply of oxygen. This completed, the enriched blood returns to the left atrium, from which it passes through the mitral valve into the left ventricle. From the left ventricle the blood passes through the...
