Prostheses and apparatuses The spare parts may replace one part of your body, e.g. an artificial knee joint or testicle. They may also be aids that support the functioning of the impaired organ, just as the pacemaker helps the heart beat.
Some spare parts are purely mechanical, e.g. a heart valve or a hip prosthesis.
Other spare parts, e.g. a pacemaker, are electronically controlled via a battery-charged computer chip. Every single spare part is designed to constitute the best possible replacement of a specific bodily function. In addition, it must be designed to match the body and it must be solid enough to function inside the body - without damaging the body or itself. The production of spare parts will develop over the years so they become better, smaller, lighter and more durable. Some parts must be soft and flexible, others hard and durable.