The human body is often compared with a complex machine. However, there is one major difference between the two. When a machine breaks down, it can be shut off until repairs are made. New parts can be ordered to replace worn-out ones. A human body cannot be shut off when repairs are needed, and new parts cannot simply be ordered.
Science, however, is finding ways to treat human disorders and replace some body parts. One solution may be an organ transplant – the replacement of a body part with an identical part from another person. Another solution may be replacement with an artificial part, or prosthesis. The design and development of artificial body parts is called biomedical engineering.
The first kidney transplant, accomplished in 1954, was a major milestone in transplant surgery. Since then about 64,000 patients have received kidney transplants. Other body parts that can be transplanted include blood, heart, lungs, cornea, liver, skin, and bone. Scientists are also studying ways to transplant the small intestine and brain tissue.
Until 1978 many transplants failed because the recipients’ bodies rejected the new organs. Rejection occurred because the body recognized a transplanted organ as a foreign substance and attacked, or rejected, the organ as it would attack invading viruses or bacteria. To prevent rejection, doctors administered drugs that suppressed all the body’s natural defenses. However, these drugs left the organ recipient susceptible to infections of all types. Today transplant recipients are given cyclosporine, an antibiotic drug that suppresses only the defenses against a transplanted organ. Since it was introduced in 1978, cyclosporine has doubled the number of transplanted organs that survive for at least a year.
Artificial Replacement Parts
Since the early 1970’s, biomedical engineers developed an amazing array of artificial parts – limbs, joints, bones, teeth, blood, hearts, and even skin. Often these prostheses involve innovative uses of modern materials and electronic equipment. For example, silicone is used in artificial skin and plastics are used in artificial joints. Researches are also designing limbs equipped with high-powered batteries and microprocessors, tiny devices that receive and channel electrical signals.
The chief aim of biomedical engineers is to design prostheses that behave like normal human parts. Some prostheses come close to achieving this goal. The Utah Arm, for example, is an artificial limb equipped with microprocessors. When attached to a person who has lost an arm, the electronic equipment picks up nerve impulses generated by the wearer’s muscles. Then the microprocessors translate the impulses into movement almost identical to those of a natural human arm.
Research is also under way on artificial organs that are part transplant and part prosthesis. One example is an artificial replacement pancreas, an important organ of digestion. Part of the artificial pancreas consists of pancreatic cells from rat that produce essential digestive juices. These cells line a system of artificial tubes in a frame of metal and plastic.