source: http://www.biomaterials.org/week/bio9.cfm
In anatomy, the heart valves are valves in the heart that maintain the unidirectional flow of blood by opening and closing depending on the difference in pressure on each side. The mechanical equivalent of the heart valves would be the reed valves.There are four valves of the heart (not counting the valve of the coronary sinus and valve of the inferior vena cava):
· The two atrioventricular (AV) valves ensure blood flows from the atria to the ventricles, and not the other way.
· The two semilunar (SL) valves are present in the arteries leaving the heart, and they prevent blood flowing back from the arteries into the ventricles. The sound of the heart valves shutting causes the heart sounds.Mechanical heart valves are prosthetics designed to replicate the function of the natural valves of the human heart. The human heart contains four valves: tricuspid valve, pulmonic valve, mitral valve and aortic valve. Their main purpose is to maintain unimpeded forward flow through the heart and from the heart into the major blood vessels connected to the heart, the pulmonary artery and the aorta. As a result of a number of disease processes, both acquired and congenital, any one of the four heart valves may malfunction and result in either stenosis (impeded forward flow) and/or backward flow (regurgitation). Either process burdens the heart and may lead to serious problems including heart failure. A mechanical heart valve is intended to replace a diseased heart valve with its prosthetic equivalent.There are two basic types of valves that can be used for aortic valve replacement, mechanical and tissue valves. Modern mechanical valves can last indefinitely (the equivalent of over 50,000 years in an accelerated valve wear tester). However, current mechanical heart valves all require lifelong treatment with a blood thinner, e.g. warfarin, which requires monthly blood tests to monitor. This process of thinning the blood is called anticoagulation. Tissue heart valves, in contrast, do not require the use of anticoagulant drugs due to the improved blood flow dynamics resulting in less red cell damage and hence less clot formation. Their main weakness however, is their limited lifespan. Traditional tissue valves, made of pig heart valves, will last on average 15 years before they require replacement
Sunday, October 18, 2009
Fodder
source: www.wikipedia.org/wiki/animalfeed
In agriculture, fodder or animal feed is any foodstuff that is used specifically to feed domesticated livestock such as cattle, goats, sheep, horses, chickens and pigs. Most animal feed is from plants but some is of animal origin. "Fodder" refers particularly to food given to the animals (including plants cut and carried to them), rather than that which they forage for themselves (see forage). It includes hay, straw, silage, compressed and pelleted feeds, oils and mixed rations, and also sprouted grains and legumes.
The worldwide animal feed industry consumed 635 million tons of feed (compound feed equivalent) in 2006, with an annual growth rate of about 2%. The use of agricultural land to grow feed rather than human food can be controversial; some types of feed, such as corn (maize), can also serve as human food, while others such as grass cannot. Some agricultural by-products which are fed to animals may be considered unsavory by human consumers.
In the past, mad cow disease spread through the inclusion of ruminant meat and bone meal in cattle feed due to prion contamination. This practice is now banned in most countries where it has occurred. Some animals have a lower tolerance for spoiled or moldy fodder than others, and certain types of molds, toxins, or poisonous weeds inadvertently mixed into a food source may cause economic losses due to sickness or death of the animals.
In agriculture, fodder or animal feed is any foodstuff that is used specifically to feed domesticated livestock such as cattle, goats, sheep, horses, chickens and pigs. Most animal feed is from plants but some is of animal origin. "Fodder" refers particularly to food given to the animals (including plants cut and carried to them), rather than that which they forage for themselves (see forage). It includes hay, straw, silage, compressed and pelleted feeds, oils and mixed rations, and also sprouted grains and legumes.
The worldwide animal feed industry consumed 635 million tons of feed (compound feed equivalent) in 2006, with an annual growth rate of about 2%. The use of agricultural land to grow feed rather than human food can be controversial; some types of feed, such as corn (maize), can also serve as human food, while others such as grass cannot. Some agricultural by-products which are fed to animals may be considered unsavory by human consumers.
In the past, mad cow disease spread through the inclusion of ruminant meat and bone meal in cattle feed due to prion contamination. This practice is now banned in most countries where it has occurred. Some animals have a lower tolerance for spoiled or moldy fodder than others, and certain types of molds, toxins, or poisonous weeds inadvertently mixed into a food source may cause economic losses due to sickness or death of the animals.
Drug Coatings
source: http://www.biomaterials.org/week/bio6.cfm
A drug is a substance, such as a pharmaceutical product, used in or on the surface of the body to diagnose, cure, mitigate, treat, or prevent disease, or to otherwise affect the structure or function of the body. It is usually synthesized outside of an organism, but introduced into an organism to produce its action. That is, when taken into the organisms body, it will produce some effects or alter some bodily functions (such as relieving symptoms, curing diseases or used as preventive medicine or any other purposes).Note that natural endogenous biochemicals (such as hormones) can bind to the same receptor in the cell, producing the same effect as a drug. Thus, drug is merely an artificial definition that distinguishes whether that molecule is synthesized within an organism or outside an organism. For instance, insulin is a hormone that is synthesized in the body; it is considered as a hormone when it is synthesized by the pancreas inside the body, but if it is introduced into the body from outside, it is considered as a drug.It is a substance which is not food,[1] and which, when ingested, affects the functioning of the mind, or the body, or both. However, under the philosophy of Chinese medicine, food is also considered a drug as it affects particular parts of body and cures some diseases. Thus, food does satisfy the above definition of drug so long as ingestion of it would alter some bodily functions.Many times drugs are encapsulated with polymers or sugars which serve as a biodegradable mechanisms that allows them to dissolve at specific parts of the digestive track.
A drug is a substance, such as a pharmaceutical product, used in or on the surface of the body to diagnose, cure, mitigate, treat, or prevent disease, or to otherwise affect the structure or function of the body. It is usually synthesized outside of an organism, but introduced into an organism to produce its action. That is, when taken into the organisms body, it will produce some effects or alter some bodily functions (such as relieving symptoms, curing diseases or used as preventive medicine or any other purposes).Note that natural endogenous biochemicals (such as hormones) can bind to the same receptor in the cell, producing the same effect as a drug. Thus, drug is merely an artificial definition that distinguishes whether that molecule is synthesized within an organism or outside an organism. For instance, insulin is a hormone that is synthesized in the body; it is considered as a hormone when it is synthesized by the pancreas inside the body, but if it is introduced into the body from outside, it is considered as a drug.It is a substance which is not food,[1] and which, when ingested, affects the functioning of the mind, or the body, or both. However, under the philosophy of Chinese medicine, food is also considered a drug as it affects particular parts of body and cures some diseases. Thus, food does satisfy the above definition of drug so long as ingestion of it would alter some bodily functions.Many times drugs are encapsulated with polymers or sugars which serve as a biodegradable mechanisms that allows them to dissolve at specific parts of the digestive track.
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