Senior Science

Topics: Blood, Heart, Ball and socket joint Pages: 26 (8826 words) Published: May 10, 2013
senior science|
Medical technologies|
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identify parts of the body and the biomaterials and biomedical devices that can be used to replace damaged or diseased body parts including: * pins, screws and plates
* artificial joints
* pacemakers
* artificial valves
* crowns, dentures
* lenses
* prosthetic limbs
* cochlear implants
Pins, screws and plates
* These are used to repair bone fractures. They are almost all made from metallic alloys. * The pin is a versatile implant used for the fixation of bone fragments and is used when the fracture is in a place where it is difficult to use a plate. * Pins are also used when it is difficult to obtain adequate stability of the bone fracture by any other means. * Screws are some of the most widely used devices for repairing fractures. They are used to fix bone plates to bones. * Bone plates are also used to repair bone fractures. They are designed to be very strong and absorb the large stress forces generated when the bone moves. * It is also important that the bone plate be fixed to the bone with the use of screws. Artificial joints

* These replace joints that have been largely destroyed by degenerative diseases such as arthritis or damaged badly in an accident. * Common examples are knee, hip and shoulder joints; the latter two are ball and socket type joints [more information on ball and socket joints is provided in 9.3 Medical Technology - Bionics, subsection 3]. * Artificial hip joints are often made from a stainless steel-polyethylene or cobalt-chromium alloy-polyethylene combination. Other materials that can be used are: * titanium

* titanium-aluminium-vanadium alloy
* ultra high molecular weight polyethylene
* metal-pyrolytic carbon coating
* metal-bioglass coating
* composites made from poly-methyl methacrylate (PMMA) and carbon fibre * porous stainless steel.
* Artificial knee joints are known to sink into the lower bone of the leg, causing crushing of the trabecular bone. To combat this problem, knee joints are now made from a layer of ultra-high molecular weight polyethylene (UHMW polyethylene) on a metal base. * Other joint replacements, such as fingers and ankles, have not been as successful, because of the complexity of movement of these joints. Pacemakers

* Pacemakers are used to correct arrhythmias, that is, when the heart beats too fast, too slowly or irregularly. A pacemaker is a battery-operated device designed to stimulate contraction of the heart at a certain rate. Some are internal (surgically implanted) and others are external. Pacemakers are connected to a small electrode, which is placed near the wall of the heart. Small electrical charges travel through a wire to the electrode, stimulating the heart to contract. * The casing of a pacemaker can be made of stainless steel or titanium. The electrodes are made from platinum or platinum-iridium alloy. Silicon rubber, polypropylene or epoxy can be used to seal parts of the pacemaker. Artificial valves

* Artificial valves can be used to replace damaged valves in the body that are no longer functioning to keep blood flowing in one direction only. * Early artificial valves in the 1960s were made from flexible leaflets, but could not withstand the fatigue for periods longer than about three years. * Most artificial valves have a fabric ring surrounding them, which allows a surgeon to sew the device into place during implantation. * Where appropriate, artificial valves are constructed from collagen-rich materials, such as pericardial tissues which have been obtained from pigs or cows and treated (to...
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