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In biology, an organism is any contiguous living system (such as animal, fungus, micro-organism, or plant). In at least some form, all types of organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homeostasis as a stable whole.

An organism may be either unicellular (a single cell) or, as in the case of humans, comprise many trillions of cells grouped into specialized tissues andorgans. The term multicellular (many cells) describes any organism made up of more than one cell.

All organisms living on Earth are divided into the eukaryotes and prokaryotes based on the presence or absence of true nuclei in their cells. The prokaryotes represent two separate domains, the Bacteria and Archaea. Eukaryotic organisms, with a membrane-bounded cell nucleus, also containorganelles, namely mitochondria and (in plants) plastids, generally considered to be derived from endosymbiotic bacteria.[1] Fungi, animals and plantsare examples of species that are eukaryotes.

In 2002 Thomas Cavalier-Smith proposed a clade, Neomura, which groups together the Archaea and Eukarya. Neomura is thought to have evolved fromBacteria, more specifically from Actinobacteria.[2] See Branching order of bacterial phyla.

Contents

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1 Etymology

2 Semantics

2.1 Non-cellular life

3 Organizational terminology

4 Chemistry

4.1 Macromolecules

5 Structure

5.1 Cell

6 Life span

7 Evolution

7.1 History of life

7.2 Horizontal gene transfer

7.3 Future of life (cloning and synthetic organisms)

8 See also

9 Notes

10 External links

[edit]Etymology

The term "organism" (Greek ὀργανισμός – organismos, from Ancient Greek ὄργανον – organon, "instrument, implement, tool, organ of sense or apprehension"[3]) first appeared in the English language in 1701 and took on its current definition by 1834 (Oxford English Dictionary). It is directly related to the term "organization". There is a long tradition of defining organisms as self-organizing beings.[4]

There has been a great deal of recent controversy about the best way to define the organism[5] and indeed about whether or not such a definition is necessary.[6] Several contributions[7] are responses to the suggestion that the category of "organism" may well not be adequate in biology.[8]

[edit]Semantics

The word organism may broadly be defined as an assembly of molecules functioning as a more or less stable whole that exhibits the properties of life. However, many sources propose definitions that exclude viruses and theoretically possible man-made non-organic life forms.[9] Viruses are dependent on the biochemical machinery of a host cell for reproduction.

Chambers Online Reference provides a broad definition: "any living structure, such as a plant, animal, fungus or bacterium, capable of growth and reproduction".[10]

In multicellular terms, "organism" usually describes the whole hierarchical assemblage of systems (for example circulatory, digestive, or reproductive) themselves collections of organs; these are, in turn, collections of tissues, which are themselves made of cells. In some plants and the nematode Caenorhabditis elegans, individual cells are totipotent.

A superorganism is an organism consisting of many individuals working together as a single functional or social unit.

[edit]Non-cellular life

Main article: Non-cellular life

Viruses are not typically considered to be organisms because they are incapable of autonomous reproduction, growth or metabolism. This controversy is problematic because some cellular organisms are also incapable of independent survival (but not of independent metabolism and procreation) and live as obligatory intracellular parasites. Although viruses have a few enzymes and molecules characteristic of living organisms, they have no metabolism of their own and cannot synthesize and organize the organic compounds that form them. Naturally, this rules out autonomous reproduction and they can only be passively replicated by the machinery of the host cell. In this sense they are similar to inanimate matter. While viruses sustain no independent metabolism, and thus are usually not accounted organisms, they do have their own genes and they do evolve by similar mechanisms by which organisms evolve.

The most common argument in support of viruses as living organisms is their ability to undergo evolution and replicate through self-assembly. Some scientists argue that viruses neither evolve, nor self- reproduce. In fact, viruses are evolved by their host cells, meaning that there was co-evolution of viruses and host cells. If host cells did not exist, viral evolution would be impossible. This is not true for cells. If viruses did not exist, the direction of evolution could be different; however, the ability to evolve would not be affected. As for the reproduction, viruses totally rely on hosts' machinery to replicate themselves.[11] The discovery of viral megagenoms with genes coding for energy metabolism and protein synthesis fueled the debate about whether viruses belong on thetree of life. The presence of these genes suggested that viruses could metabolize in the past. It was found later that the genes coding for energy and protein metabolism have cellular origin. Most likely, they were acquired through horizontal gene transfer from viral hosts.[12]

Another good argument against placing viruses on the tree of life[not relevant] is their polyphyletic origin.[13] Viruses do not share homologous characteristics neither with cellular organisms, nor with other viruses. Since it is impossible to trace viral evolution back to the last universal ancestor, it is also impossible to place them on the tree of life, which is based on the gene homology.

[edit]Organizational terminology

The hierarchy of biological classification's eight majortaxonomic ranks. Intermediate minor rankings are not shown.

All organisms are classified by the science of alpha taxonomy into either taxa or clades.

Taxa are ranked groups of organisms, which run from the general (domain) to the specific (species). A broad scheme of ranks in hierarchical order is:

Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species

To give an example, Homo sapiens is the Latin binomial equating to modern humans. All members of the species sapiens are, at least in theory, genetically able to interbreed. Several species may belong to a genus, but the members of different species within a genus are unable to interbreed to produce fertile offspring. Homo, however, only has one surviving species (sapiens), Homo erectus, Homo neanderthalensis, etc. having become extinct thousands of years ago. Several genera belong to the same family and so on up the hierarchy. Eventually, the relevant kingdom (Animalia, in the case of humans) is placed into one of the three domains depending upon certain genetic and structural characteristics.

All living organisms known to science are given classification by this system such that the species within a particular family are more closely related and genetically similar than the species within a particular phylum.

Since viruses are not living organisms, their classification is a challenging task. At first, viruses were classified according to their hosts: plant viruses, animal viruses, bacteriophages. Later, they were classified by the disease that they cause. For example, respiratory viruses, enterics. Now, viruses are classified based on the nucleic acid content, capsid symmetry and the presence or absence of the envelope.

[edit]Chemistry

Organisms are complex chemical systems, organized in ways that promote reproduction and some measure of sustainability or survival. The same laws that govern non-living chemistry govern the chemical processes of life. It is generally the phenomena of entire organisms that determine their fitness to an environment and therefore the survivability of their DNA-based genes.

Organisms clearly owe their origin, metabolism, and many other internal functions to chemical phenomena, especially the chemistry of large organic molecules. Organisms are complex systems of chemical compounds that, through interaction and environment, play a wide variety of roles.

Organisms are semi-closed chemical systems. Although they are individual units of life (as the definition requires), they are not closed to the environment around them. To operate they constantly take in and release energy. Autotrophs produce usable energy (in the form of organic compounds) using light from the sun or inorganic compounds while heterotrophs take in organic compounds from the environment.

The primary chemical element in these compounds is carbon. The physical properties of this element such as its great affinity for bonding with other small atoms, including other carbon atoms, and its small size making it capable of forming multiple bonds, make it ideal as the basis of organic life. It is able to form small three-atom compounds (such as carbon dioxide), as well as large chains of many thousands of atoms that can store data (nucleic acids), hold cells together, and transmit information (protein).

[edit]Macromolecules

Compounds that make up organisms may be divided into macromolecules and other, smaller molecules. The four groups of macromolecule are nucleic acids, proteins, carbohydrates and lipids. Nucleic acids (specifically deoxyribonucleic acid, or DNA) store genetic data as a sequence of nucleotides. The particular sequence of the four different types of nucleotides (adenine, cytosine,guanine, and thymine) dictate many characteristics that constitute the organism. The sequence is divided up into codons, each of which is a particular sequence of three nucleotides and corresponds to a particular amino acid. Thus a sequence of DNA codes for a particular protein that, due to the chemical properties of the amino acids it is made from, folds in a particular manner and so performs a particular function.

These protein functions have been recognized:

Enzymes, which catalyze all of the reactions of metabolism

Structural proteins, such as tubulin, or collagen

Regulatory proteins, such as transcription factors or cyclins that regulate the cell cycle

Signaling molecules or their receptors such as some hormones and their receptors

Defensive proteins, which can include everything from antibodies of the immune system, to toxins (e.g., dendrotoxins of snakes), to proteins that include unusual amino acids likecanavanine

Lipids make up the membrane of cells that constitutes a barrier, containing everything within the cell and preventing compounds from freely passing into, and out of, the cell.Due to the selective permeability of the phospholipid membraine only specific compounds can pass through it.In some multicellular organisms they serve as a storage of energy and mediate communication between cells.Carbohydrates are more easily broken down than lipids and yield more energy to compare to lipids and proteins.In fact, carbohydrates are the number one source of energy for all living organisms.

[edit]Structure

All organisms consist of monomeric units called cells; some contain a single cell (unicellular) and others contain many units (multicellular). Multicellular organisms are able to specialize cells to perform specific functions. A group of such cells is a tissue, and in animals these occur as four basic types, namely epithelium, nervous tissue, muscle tissue, and connective tissue. Several types of tissue work together in the form of an organ to produce a particular function (such as the pumping of the blood by the heart, or as a barrier to the environment as the skin). This pattern continues to a higher level with several organs functioning as an organ system to allow for reproduction, digestion, etc. Many multicell organisms consist of several organ systems, which coordinate to allow for life.

[edit]Cell

The cell theory, first developed in 1839 by Schleiden and Schwann, states that all organisms are composed of one or more cells; all cells come from preexisting cells; all vital functions of an organism occur within cells, and cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells.

There are two types of cells, eukaryotic and prokaryotic. Prokaryotic cells are usually singletons, while eukaryotic cells are usually found in multicellular organisms. Prokaryotic cells lack anuclear membrane so DNA is unbound within the cell, eukaryotic cells have nuclear membranes.

All cells, whether prokaryotic or eukaryotic, have a membrane, which envelops the cell, separates its interior from its environment, regulates what moves in and out, and maintains the electric potential of the cell. Inside the membrane, a salty cytoplasm takes up most of the cell volume. All cells possess DNA, the hereditary material of genes, and RNA, containing the information necessary to build various proteins such as enzymes, the cell's primary machinery. There are also other kinds of biomolecules in cells.

All cells share several similar characteristics of:[14]

Reproduction by cell division (binary fission, mitosis or meiosis).

Use of enzymes and other proteins coded by DNA genes and made via messenger RNA intermediates and ribosomes.

Metabolism, including taking in raw materials, building cell components, converting energy, molecules and releasing by-products. The functioning of a cell depends upon its ability to extract and use chemical energy stored in organic molecules. This energy is derived from metabolic pathways.

Response to external and internal stimuli such as changes in temperature, pH or nutrient levels.

Cell contents are contained within a cell surface membrane that contains proteins and a lipid bilayer.

[edit]Life span

One of the basic parameters of an organism is its life span. Some organisms live as short as one day, while some plants and fungi can live thousands of years.

[edit]Evolution

See also: Common descent and Origin of life

In biology, the theory of universal common descent proposes that all organisms on Earth are descended from a common ancestor or ancestral gene pool. Evidence for common descent may be found in traits shared between all living organisms. In Darwin's day, the evidence of shared traits was based solely on visible observation of morphologic similarities, such as the fact that all birds have wings, even those that do not fly.

Today, there is debate over whether or not all organisms descended from a common ancestor, or a "last universal ancestor" (LUA), also called the "last universal common ancestor" (LUCA), the hypothetical unicellular organism or single cell that gave rise to all life on Earth 3.5 to 3.8 billion years ago.[15] The universality of genetic coding suggests common ancestry. For example, every living cell makes use of nucleic acids as its genetic material, and uses the same twenty amino acids as the building blocks for proteins, although exceptions to the basic twenty amino acids have been found. However, throughout history groupings based on appearance or function of species have sometimes been polyphyletic due to convergent evolution.

It was once thought that the genetic code was invariably universal (see: Universal genetic code), but many variations have been discovered[16] including various alternative mitochondrial codes.[17]Back in the early 1970s, evolutionary biologists thought that a given piece of DNA specified the same protein subunit in every living thing, and that the genetic code was thus universal. This was interpreted as evidence that every organism had inherited its genetic code from a single common ancestor, aka, an LUCA. In 1979, however, exceptions to the code were found in mitochondria, the tiny energy factories inside cells. Researchers studying human mitochondrial genes discovered that they used an alternative code, and many slight variants have been discovered since,[16]including various alternative mitochondrial codes,[17] as well as small variants such as Mycoplasma translating the codon UGA as tryptophan. Biologists subsequently found exceptions in bacteria and in the nuclei of algae and single-cell animals. For example, certain proteins may use alternative initiation (start) codons not normally used by that species.[18] In certain proteins, non-standard amino acids are substituted for standard stop codons, depending upon associated signal sequences in the messenger RNA: UGA can code for selenocysteine and UAG can code for pyrrolysine. Selenocysteine is now viewed as the 21st amino acid, and pyrrolysine is viewed as the 22nd. A detailed description of variations in the genetic code can be found at the NCBI web site.

A hypothetical phylogenetic tree of all extant organisms, based on 16S rRNA genesequence data, showing the evolutionary history of the three domains of life, bacteria,archaea, and eukaryotes. Originally proposed by Carl Woese.

Information about the early development of life includes input from many different fields, including geology and planetary science. These sciences provide information about the history of the Earth and the changes produced by life. However, a great deal of information about the early Earth has been destroyed by geological processes over the course of time.

[edit]History of life

Main article: Timeline of evolution

The chemical evolution from self-catalytic chemical reactions to life (see Origin of life) is not a part of biological evolution, but it is unclear at which point such increasingly complex sets of reactions became what we would consider, today, to be living organisms.

Precambrian stromatolites in the Siyeh Formation,Glacier National Park. In 2002, William Schopf of UCLApublished a controversial paper in the journal Naturearguing that formations such as this possess 3.5 billion year old fossilized algae microbes. If true, they would be the earliest known life on earth.

Little is known about the earliest developments in life. However, all existing organisms share certain traits, including cellular structure andgenetic code. Most scientists interpret this to mean all existing organisms share a common ancestor, which had already developed the most fundamental cellular processes, but there is no scientific consensus on the relationship of the three domains of life (Archaea, Bacteria, Eukaryota) or the origin of life. Attempts to shed light on the earliest history of life generally focus on the behavior of macromolecules, particularly RNA, and the behavior of complex systems.

The emergence of oxygenic photosynthesis (around 3 billion years ago) and the subsequent emergence of an oxygen-rich, non-reducing atmosphere can be traced through the formation of banded iron deposits, and later red beds of iron oxides. This was a necessary prerequisite for the development of aerobic cellular respiration, believed to have emerged around 2 billion years ago.

In the last billion years, simple multicellular plants and animals began to appear in the oceans. Soon after the emergence of the first animals, the Cambrian explosion (a period of unrivaled and remarkable, but brief, organismal diversity documented in the fossils found at the Burgess Shale) saw the creation of all the major body plans, or phyla, of modern animals. This event is now believed to have been triggered by the development of the Hox genes. About 500 million years ago, plants and fungi colonized the land, and were soon followed by arthropods and other animals, leading to the development of today's land ecosystems.

The evolutionary process may be exceedingly slow. Fossil evidence indicates that the diversity and complexity of modern life has developed over much of the history of the earth. Geological evidence indicates that the Earth is approximately 4.6 billion years old. Studies on guppies by David Reznick at the University of California, Riverside, however, have shown that the rate of evolution through natural selection can proceed 10 thousand to 10 million times faster than what is indicated in the fossil record.[19] Such comparative studies however are invariably biased by disparities in the time scales over which evolutionary change is measured in the laboratory, field experiments, and the fossil record.

[edit]Horizontal gene transfer

Main article: Horizontal gene transfer

The ancestry of living organisms has traditionally been reconstructed from morphology, but is increasingly supplemented with phylogenetics—the reconstruction of phylogenies by the comparison of genetic (DNA) sequence.

Sequence comparisons suggest recent horizontal transfer of many genes among diverse species including across the boundaries of phylogenetic "domains". Thus determining the phylogenetic history of a species can not be done conclusively by determining evolutionary trees for single genes.[20]

Biologist Gogarten suggests "the original metaphor of a tree no longer fits the data from recent genome research", therefore "biologists (should) use the metaphor of a mosaic to describe the different histories combined in individual genomes and use (the) metaphor of a net to visualize the rich exchange and cooperative effects of HGT among microbes."[21]

[edit]Future of life (cloning and synthetic organisms)

In modern terms, the category of organism cloning refers to the procedure of creating a new multicellular organism, genetically identical to another. However, cloning also has the potential of creating entirely new species of organisms. Organism cloning is the subject of much ethical debate. (see Bioethics, Ethics of cloning, and Designer baby articles)

The J. Craig Venter Institute has recently[when?] assembled a synthetic bacterial genome, Mycoplasma genitalium, by using recombination in yeast of 25 overlapping DNA fragments in a single step. "The use of yeast recombination greatly simplifies the assembly of large DNA molecules from both synthetic and natural fragments."[22] Other companies, such as Synthetic Genomics, have already been formed to take advantage of the many commercial uses of custom designed genomes.

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A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specificsymptoms and signs.[1] It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such asautoimmune diseases. In humans, "disease" is often used more broadly to refer to any condition that causes pain, dysfunction, distress, social problems, or death to the person afflicted, or similar problems for those in contact with the person. In this broader sense, it sometimes includes injuries,disabilities, disorders, syndromes, infections, isolated symptoms, deviant behaviors, and atypical variations of structure and function, while in other contexts and for other purposes these may be considered distinguishable categories. Diseases usually affect people not only physically, but also emotionally, as contracting and living with many diseases can alter one's perspective on life, and their personality.

Death due to disease is called death by natural causes. There are four main types of disease: pathogenic disease, deficiency disease, hereditary disease, and physiological disease.

Diseases can also be classified as communicable and non-communicable disease.

Contents

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1 Terminology

1.1 Concepts

1.2 Types

1.3 Stages

1.4 Scope

2 Causes and transmissibility

3 Burdens of disease

4 Prevention

5 Treatments

6 Epidemiology

7 Social and cultural responses

7.1 Language of disease

8 See also

9 References

10 External links

[edit]Terminology

[edit]Concepts

In many cases, the terms disease, disorder, morbidity and illness are used interchangeably.[2] In some situations, specific terms are considered preferable.

DiseaseThe term disease broadly refers to any condition that impairs normal function, and is therefore associated with dysfunction of normal homeostasis.[3] Commonly, term disease is used to refer specifically to infectious diseases, which are clinically evident diseases that result from the presence of pathogenic microbial agents, including viruses, bacteria, fungi, protozoa, multicellular organisms, and aberrant proteins known as prions. An infection that does not and will not produce clinically evident impairment of normal functioning, such as the presence of the normalbacteria and yeasts in the gut or of a passenger virus, is not considered a disease; by contrast, an infection that is asymptomatic during its incubation period, but expected to produce symptoms later, is usually considered a disease. Non-infectious diseases are all other diseases, including most forms of cancer, heart disease, and genetic disease.IllnessIllness and sickness are generally used as synonyms for disease.[4] However, this term is occasionally used to refer specifically to the patient's personal experience of their disease.[5][6] In this model, it is possible for a person to be diseased without being ill (to have an objectively definable, but asymptomatic, medical condition), and to be ill without being diseased (such as when a person perceives a normal experience as a medical condition, or medicalizes a non-disease situation in his or her life). Illness is often not due to infection but a collection of evolved responses, sickness behavior, by the body which aids the clearing of infection. Such aspects of illness can include lethargy, depression, anorexia, sleepiness, hyperalgesia, and inability toconcentrate.[7][8][9]DisorderIn medicine, a disorder is a functional abnormality or disturbance. Medical disorders can be categorized into mental disorders, physical disorders, genetic disorders, emotional and behavioral disorders, and functional disorders. The term disorder is often considered more value-neutral and less stigmatizing than the terms disease or illness, and therefore is preferred terminology in some circumstances. In mental health, the term mental disorder is used as a way of acknowledging the complex interaction of biological, social, and psychological factors in psychiatricconditions. However, the term disorder is also used in many other areas of medicine, primarily to identify physical disorders that are not caused by infectious organisms, such as metabolic disorders.Medical conditionA medical condition is a broad term that includes all diseases and disorders. While the term medical condition generally includes mental illnesses, in some contexts the term is used specifically to denote any illness, injury, or disease except for mental illnesses. The Diagnostic and Statistical Manual of Mental Disorders (DSM), the widely used psychiatric manual that defines all mental disorders, uses the term general medical condition to refer to all diseases, illnesses, and injuries except for mental disorders.[10] This usage is also commonly seen in the psychiatric literature. Some health insurance policies also define a medical condition as any illness, injury, or disease except for psychiatric illnesses.[11]As it is more value-neutral than terms like disease, the term medical condition is sometimes preferred by people with health issues that they do not consider to be deleterious. On the other hand, by emphasizing the medical nature of the condition, this term is sometimes rejected, such as by proponents of the autism rights movement.The term medical condition is also used as a synonym for medical state, in which case it describes an individual patient's current state, as seen from a medical standpoint. This usage is seen in statements that describe a patient as being "in critical condition", for example.MorbidityMorbidity (from Latin morbidus, meaning "sick, unhealthy") is a diseased state, disability, or poor health due to any cause.[12] The term may be used to refer to the existence of any form of disease, or to the degree that the health condition affects the patient. Among severely ill patients, the level of morbidity is often measured by ICU scoring systems. Comorbidity is the simultaneous presence of two or more medical conditions, such as schizophrenia and substance abuse.In epidemiology and actuarial science, the term morbidity rate can refer to either the incidence rate, or the prevalence of a disease or medical condition. This measure of sickness is contrasted with the mortality rate of a condition, which is the proportion of people dying during a given time interval.SyndromeA syndrome is the association of several medical signs, symptoms, and or other characteristics that often occur together. Some syndromes, such as Down syndrome, have only one cause; others, such as Parkinsonian syndrome, have multiple possible causes. In other cases, the cause of the syndrome is unknown. A familiar syndrome name often continues to be used even after an underlying cause has been found, or when there are a number of different possible primary causes.PrediseasePredisease is a type of disease creep or medicalization in which currently healthy people with risk factors for disease, but no evidence of actual disease, are told that they are sick.Prediabetes and prehypertension are common examples. Labeling a healthy person with predisease can result in overtreatment, such as taking drugs that only help people with severe disease, or in useful preventive measures, such as motivating the person to get a healthful amount of physical exercise.[13]

[edit]Types

Fat diseasesGay diseasesVagina illnessFoodborne illness or food poisoning is any illness resulting from the consumption of food contaminated with pathogenic bacteria, toxins, viruses, prions or parasites.Communicable diseasesNon-communicable diseasesAirborne diseasesLifestyle diseasesMental disordersMental illness is a broad, generic label for a category of illnesses that may include affective or emotional instability, behavioral dysregulation, and/or cognitive dysfunction or impairment. Specific illnesses known as mental illnesses include major depression, generalized anxiety disorder, schizophrenia, and attention deficit hyperactivity disorder, to name a few. Mental illness can be of biological (e.g., anatomical, chemical, or genetic) or psychological (e.g., trauma or conflict) origin. It can impair the affected person's ability to work or school and harm interpersonal relationships. The term insanity is used technically as a legal term.Organic diseaseAn organic disease is one caused by a physical or physiological change to some tissue or organ of the body. The term sometimes excludes infections. It is commonly used in contrast with mental disorders. It includes emotional and behavioral disorders if they are due to changes to the physical structures or functioning of the body, such as after a stroke or a traumatic brain injury, but not if they are due to psychosocial issues.

[edit]Stages

"Flareup" redirects here. For the Transformers character, see Flareup (Transformers).

In an infectious disease, the incubation period is the time between infection and the appearance of symptoms. The latency period is the time between infection and the ability of the disease to spread to another person, which may precede, follow, or be simultaneous with the appearance of symptoms. Some viruses also exhibit a dormant phase, called viral latency, in which the virus hides in the body in an inactive state. For example, varicella zoster virus causes chickenpox in the acute phase; after recovery from chickenpox, the virus may remain dormant in nerve cells for many years, and later cause herpes zoster (shingles).

Acute diseaseAn acute disease is a short-lived disease, like the common cold.Chronic diseaseA chronic disease is one that lasts for a long time, usually at least six months. During that time, it may be constantly present, or it may go into remission and periodically relapse. A chronic disease may be stable (does not get any worse) or it may be progressive (gets worse over time). Some chronic diseases can be permanently cured. Most chronic diseases can be beneficially treated, even if they cannot be permanently cured.Flare-upA flare-up can refer to either the recurrence of symptoms or an onset of more severe symptoms.Refractory diseaseA refractory disease is a disease that resists treatment, especially an individual case that resists treatment more than is normal for the specific disease in question.Progressive diseaseProgressive disease is a disease whose typical natural course is the worsening of the disease until death, serious debility, or organ failure occurs. Slowly progressive diseases are also chronic diseases; many are also degenerative diseases. The opposite of progressive disease is stable disease or static disease: a medical condition that exists, but does not get better or worse.CureA cure is the end of a medical condition or a treatment that is very likely to end it, while remission refers to the disappearance, possibly temporarily, of symptoms. Complete remission is the best possible outcome for incurable diseases.

[edit]Scope

Localized diseaseA localized disease is one that affects only one part of the body, such as athlete's foot or an eye infection.Disseminated diseaseA disseminated disease has spread to other parts; with cancer, this is usually called metastatic disease.Systemic diseaseA systemic disease is a disease that affects the entire body, such as influenza or high blood pressure.

[edit]Causes and transmissibility

Main article: Transmission (medicine)

Only some diseases such as influenza are contagious and commonly believed to be infectious. The micro-organisms that cause these diseases are known as pathogens and include varieties of bacteria, viruses, protozoa and fungi. Infectious diseases can be transmitted, e.g. by hand-to-mouth contact with infectious material on surfaces, by bites of insects or other carriers of the disease, and from contaminated water or food (often via faecal contamination), etc.[14] In addition, there are sexually transmitted diseases. In some cases, micro-organisms that are not readily spread from person to person play a role, while other diseases can be prevented or ameliorated with appropriate nutrition or other lifestyle changes.

Some diseases, such as most (but not all) forms of cancer, heart disease and mental disorders, are non-infectious diseases. Many non-infectious diseases have a partly or completely genetic basis (see genetic disorder) and may thus be transmitted from one generation to another.

Social determinants of health are the social conditions in which people live which determine their health. Illnesses are generally related to social, economic, political, and environmental circumstances. Social determinants of health have been recognized by several health organizations such as the Public Health Agency of Canada and the World Health Organization to greatly influence collective and personal well-being. The World Health Organization's Social Determinants Council also recognizes Social determinants of health in poverty.

When the cause of a disease is poorly understood, societies tend to mythologize the disease or use it as a metaphor or symbol of whatever that culture considers to be evil. For example, until the bacterial cause of tuberculosis was discovered in 1882, experts variously ascribed the disease to heredity, a sedentary lifestyle, depressed mood, and overindulgence in sex, rich food, or alcohol—all the social ills of the time.[15]

[edit]Burdens of disease

Disease burden is the impact of a health problem in an area measured by financial cost, mortality, morbidity, or other indicators.

There are several measures used to quantify the burden imposed by diseases on people. The years of potential life lost (YPLL) is a simple estimate of the number of years that a person's life was shortened due to a disease. For example, if a person dies at the age of 65 from a disease, and would probably have lived until age 80 without that disease, then that disease has caused a loss of 15 years of potential life. YPLL measurements do not account for how disabled a person is before dying, so the measurement treats a person who dies suddenly and a person who died at the same age after decades of illness as equivalent. In 2004, the World Health Organization calculated that 932 million years of potential life were lost to premature death.[16]

The quality-adjusted life year (QALY) and disability-adjusted life year (DALY) metrics are similar, but take into account whether the person was healthy after diagnosis. In addition to the number of years lost due to premature death, these measurements add part of the years lost to being sick. Unlike YPLL, these measurements show the burden imposed on people who are very sick, but who live a normal lifespan. A disease that has high morbidity, but low mortality, will have a high DALY and a low YPLL. In 2004, the World Health Organization calculated that 1.5 billion disability-adjusted life years were lost to disease and injury.[16]

Disease categoryPercent of all YPLLs lost, worldwide[16]Percent of all DALYs lost, worldwide[16]Percent of all YPLLs lost, Europe[16]Percent of all DALYs lost, Europe[16]Percent of all YPLLs lost, US and Canada[16]Percent of all DALYs lost, US and Canada[16]Infectious and parasitic diseases, especially lower respiratory tract infections,diarrhea, AIDS, tuberculosis, and malaria37%26%9%6%5%3%Neuropsychiatric conditions, e.g. depression2%13%3%19%5%28%Injuries, especially motor vehicle accidents14%12%18%13%18%10%Cardiovascular diseases, principally heart attacks and stroke14%10%35%23%26%14%Premature birth and other perinatal deaths11%8%4%2%3%2%Cancer8%5%19%11%25%13%

[edit]Prevention

Main article: Preventive medicine

Many diseases and disorders can be prevented through a variety of means. These include sanitation, proper nutrition, adequate exercise, vaccinations, and other self-care and public healthmeasures.

[edit]Treatments

Main article: Therapy

Medical therapies or treatments are efforts to cure or improve a disease or other health problem. In the medical field, therapy is synonymous with the word treatment. Among psychologists, the term may refer specifically to psychotherapy or "talk therapy". Common treatments include medications, surgery, medical devices, and self-care. Treatments may be provided by an organizedhealth care system, or informally, by the patient or family members.

A prevention or preventive therapy is a way to avoid an injury, sickness, or disease in the first place. A treatment or cure is applied after a medical problem has already started. A treatment attempts to improve or remove a problem, but treatments may not produce permanent cures, especially in chronic diseases. Cures are a subset of treatments that reverse diseases completely or end medical problems permanently. Many diseases that cannot be completely cured are still treatable. Pain management (also called pain medicine) is that branch of medicine employing an interdisciplinary approach to the relief of pain and improvement in the quality of life of those living with pain[17]

Treatment for medical emergencies must be provided promptly, often through an emergency department or, in less critical situations, through an urgent care facility.

[edit]Epidemiology

Main article: Epidemiology

Epidemiology is the study of the factors that cause or encourage diseases. Some diseases are more common in certain geographic areas, among people with certain genetic or socioeconomic characteristics, or at different times of the year.

Epidemiology is considered a cornerstone methodology of public health research, and is highly regarded in evidence-based medicine for identifying risk factors for disease. In the study of communicable and non-communicable diseases, the work of epidemiologists ranges from outbreak investigation to study design, data collection and analysis including the development of statistical models to test hypotheses and the documentation of results for submission to peer-reviewed journals. Epidemiologists also study the interaction of diseases in a population, a condition known as a syndemic. Epidemiologists rely on a number of other scientific disciplines such as biology (to better understand disease processes), biostatistics (the current raw information available), Geographic Information Science (to store data and map disease patterns) and social science disciplines (to better understand proximate and distal risk factors). Epidemiology can help identify causes as well as guide prevention efforts.

In studying diseases, epidemiology faces the challenge of defining them. Especially for poorly understood diseases, different groups might use significantly different definitions. Without an agreed-upon definition, different researchers will find very different numbers of cases and characteristics of the disease.[18]

[edit]Social and cultural responses

Obesity was a status symbol in Renaissance culture: "The Tuscan General Alessandro del Borro", attributed to Andrea Sacchi, 1645.[19] It is now generally regarded as a disease.

How a society responds to diseases is the subject of medical sociology.

A condition may be considered to be a disease in some cultures or eras but not in others. For example, obesity can represent wealth and abundance, and is a status symbol in famine-prone areas and some places hard-hit by HIV/AIDS.[20] Epilepsy is considered a sign of spiritual gifts among the Hmong people.[21]

Sickness confers the social legitimization of certain benefits, such as illness benefits, work avoidance, and being looked after by others. The person who is sick takes on a social role called the sick role. A person who responds to a dreaded disease, such as cancer, in a culturally acceptable fashion may be publicly and privately honored with higher social status.[22] In return for these benefits, the sick person is obligated to seek treatment and work to become well once more. As a comparison, consider pregnancy, which is not interpreted as a disease or sickness, even if the mother and baby may both benefit from medical care.

Most religions grant exceptions from religious duties to people who are sick. For example, one whose life would be endangered by fasting on Yom Kippur or during Ramadan is exempted from the requirement, or even forbidden from participating. People who are sick are also exempted from social duties. For example, ill health is the only socially acceptable reason for an American to refuse an invitation to the White House.[23]

The identification of a condition as a disease, rather than as simply a variation of human structure or function, can have significant social or economic implications. The controversial recognitions as diseases of repetitive stress injury (RSI) and post-traumatic stress disorder (also known as "Soldier's heart", "shell shock", and "combat fatigue") has had a number of positive and negative effects on the financial and other responsibilities of governments, corporations and institutions towards individuals, as well as on the individuals themselves. The social implication of viewing aging as a disease could be profound, though this classification is not yet widespread.

Lepers were people who were historically shunned because they had an infectious disease, and the term "leper" still evokes social stigma. Fear of disease can still be a widespread social phenomenon, though not all diseases evoke extreme social stigma.

Social standing and economic status affect health. Diseases of poverty are diseases that are associated with poverty and low social status; diseases of affluence are diseases that are associated with high social and economic status. Which diseases are associated with which states varies according to time, place, and technology. Some diseases, such as diabetes mellitus, may be associated with both poverty (poor food choices) and affluence (long lifespans and sedentary lifestyles), through different mechanisms. The term diseases of civilization describes diseases that are more common among older people. For example, cancer is far more common in societies in which most members live until they reach the age of 80 than in societies in which most members die before they reach the age of 50.

[edit]Language of disease

An illness narrative is a way of organizing a medical experience into a coherent story that illustrates the sick individual's personal experience.

People use metaphors to make sense of their experiences with disease. The metaphors move disease from an objective thing that exists to an affective experience. The most popular metaphors draw on military concepts: Disease is an enemy that must be feared, fought, battled, and routed. The patient or the healthcare provider is a warrior, rather than a passive victim or bystander. The agents of communicable diseases are invaders; non-communicable diseases constitute internal insurrection or civil war. Because the threat is urgent, perhaps a matter of life and death, unthinkably radical, even oppressive, measures are society's and the patient's moral duty as they courageously mobilize to struggle against destruction. The War on Cancer is an example of this metaphorical use of language.[24]

Another class of metaphors describes the experience of illness as a journey: The person travels to or from a place of disease, and changes himself, discovers new information, or increases his experience along the way. He may travel "on the road to recovery" or make changes to "get on the right track".[24] Some are explicitly immigration-themed: the patient has been exiled from the home territory of health to the land of the ill, changing identity and relationships in the process.[25]

Some metaphors are disease-specific. Slavery is a common metaphor for addictions: The alcoholic is enslaved by drink, and the smoker is captive to nicotine. Some cancer patients treat the loss of their hair from chemotherapy as a metonymy or metaphor for all the losses caused by the disease.[24]

Some diseases are used as metaphors for social ills: "Cancer" is a common description for anything that is endemic and destructive in society, such as poverty, injustice, or racism. AIDS was seen as a divine judgment for moral decadence, and only by purging itself from the "pollution" of the "invader" could society become healthy again.[24] Authors in the 19th century commonly used tuberculosis as a symbol and a metaphor for transcendence. Victims of the disease were portrayed in literature as having risen above daily life to become ephemeral objects of spiritual or artistic achievement. In the 20th century, after its cause was better understood, the same disease became the emblem of poverty, squalor, and other social problems.

[nolovefromjames-blog]

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Medicine is the applied science or practice of the diagnosis, treatment, and prevention of disease.[1] It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness in human beings.

Contemporary medicine applies health science, biomedical research, and medical technology to diagnose and treat injury and disease, typically throughmedication or surgery, but also through therapies as diverse as psychotherapy, external splints & traction, prostheses, biologics, ionizing radiation and others.

The word medicine is derived from the Latin ars medicina, meaning the art of healing.[2][3]

Contents

  [hide] 

1 Clinical practice

2 Institutions

2.1 Delivery

3 Branches

3.1 Basic sciences

3.2 Specialties

3.2.1 Surgery

3.2.2 'Medicine' as a specialty

3.2.3 Diagnostic specialties

3.2.4 Other major specialties

3.3 Interdisciplinary fields

4 Education

5 Medical ethics

6 Legal controls

7 Criticism of modern medicine

8 Honors and awards

9 History

9.1 Ancient world

9.2 Middle ages

9.3 Modern

10 Patron saints

11 See also

12 References

13 External links

[edit]Clinical practice

It has been suggested that Medical practice be merged into this article or section. (Discuss) Proposed since August 2011.

The Doctor, by Sir Luke Fildes (1891)

In clinical practice, doctors personally assess patients in order to diagnose, treat, and prevent disease using clinical judgment. The doctor-patient relationship typically begins an interaction with an examination of the patient's medical history and medical record, followed a medical interview[4]and a physical examination. Basic diagnostic medical devices (e.g. stethoscope, tongue depressor) are typically used. After examination for signsand interviewing for symptoms, the doctor may order medical tests (e.g. blood tests), take a biopsy, or prescribe pharmaceutical drugs or other therapies. Differential diagnosis methods help to rule out conditions based on the information provided. During the encounter, properly informing the patient of all relevant facts is an important part of the relationship and the development of trust. The medical encounter is then documented in the medical record, which is a legal document in many jurisdictions.[5] Followups may be shorter but follow the same general procedure.

The components of the medical interview[4] and encounter are:

Chief complaint (cc): the reason for the current medical visit. These are the 'symptoms.' They are in the patient's own words and are recorded along with the duration of each one. Also called 'presenting complaint.'

History of present illness / complaint (HPI): the chronological order of events of symptoms and further clarification of each symptom.

Current activity: occupation, hobbies, what the patient actually does.

Medications (Rx): what drugs the patient takes including prescribed, over-the-counter, and home remedies, as well as alternative and herbal medicines/herbal remedies. Allergies are also recorded.

Past medical history (PMH/PMHx): concurrent medical problems, past hospitalizations and operations, injuries, past infectious diseases and/or vaccinations, history of known allergies.

Social history (SH): birthplace, residences, marital history, social and economic status, habits (including diet, medications, tobacco, alcohol).

Family history (FH): listing of diseases in the family that may impact the patient. A family tree is sometimes used.

Review of systems (ROS) or systems inquiry: a set of additional questions to ask, which may be missed on HPI: a general enquiry (have you noticed any weight loss, change in sleep quality, fevers, lumps and bumps? etc.), followed by questions on the body's main organ systems (heart, lungs, digestive tract, urinary tract, etc.).

The physical examination is the examination of the patient looking for signs of disease ('Symptoms' are what the patient volunteers, 'Signs' are what the healthcare provider detects by examination). The healthcare provider uses the senses of sight, hearing, touch, and sometimes smell (e.g., in infection, uremia, diabetic ketoacidosis). Taste has been made redundant by the availability of modern lab tests. Four actions are taught as the basis of physical examination: inspection, palpation (feel), percussion (tap to determine resonance characteristics), and auscultation(listen). This order may be modified depending on the main focus of the examination (e.g., a joint may be examined by simply "look, feel, move". Having this set order is an educational tool that encourages practitioners to be systematic in their approach and refrain from using tools such as the stethoscope before they have fully evaluated the other modalities).

The clinical examination involves study of:

Vital signs including height, weight, body temperature, blood pressure, pulse, respiration rate, hemoglobin oxygen saturation

General appearance of the patient and specific indicators of disease (nutritional status, presence of jaundice, pallor or clubbing)

Skin

Head, eye, ear, nose, and throat (HEENT)

Cardiovascular (heart and blood vessels)

Respiratory (large airways and lungs)

Abdomen and rectum

Genitalia (and pregnancy if the patient is or could be pregnant)

Musculoskeletal (including spine and extremities)

Neurological (consciousness, awareness, brain, vision, cranial nerves, spinal cord and peripheral nerves)

Psychiatric (orientation, mental state, evidence of abnormal perception or thought).

It is to likely focus on areas of interest highlighted in the medical history and may not include everything listed above.

Laboratory and imaging studies results may be obtained, if necessary.

The medical decision-making (MDM) process involves analysis and synthesis of all the above data to come up with a list of possible diagnoses (the differential diagnoses), along with an idea of what needs to be done to obtain a definitive diagnosis that would explain the patient's problem.

The treatment plan may include ordering additional laboratory tests and studies, starting therapy, referral to a specialist, or watchful observation. Follow-up may be advised.

This process is used by primary care providers as well as specialists. It may take only a few minutes if the problem is simple and straightforward. On the other hand, it may take weeks in a patient who has been hospitalized with bizarre symptoms or multi-system problems, with involvement by several specialists.

On subsequent visits, the process may be repeated in an abbreviated manner to obtain any new history, symptoms, physical findings, and lab or imaging results or specialist consultations.

[edit]Institutions

The Hospital of Santa Maria della Scala, fresco by Domenico di Bartolo, 1441–1442

Contemporary medicine is in general conducted within health care systems. Legal, credentialing and financing frameworks are established by individual governments, augmented on occasion by international organizations. The characteristics of any given health care system have significant impact on the way medical care is provided.

Advanced industrial countries (with the exception of the United States)[6][7] and many developing countries provide medical services through a system ofuniversal health care that aims to guarantee care for all through a single-payer health care system, or compulsory private or co-operative health insurance. This is intended to ensure that the entire population has access to medical care on the basis of need rather than ability to pay. Delivery may be via private medical practices or by state-owned hospitals and clinics, or by charities, most commonly by a combination of all three.

Most tribal societies, and the United States,[6][7] provide no guarantee of healthcare for the population as a whole. In such societies, healthcare is available to those that can afford to pay for it or have self-insured it (either directly or as part of an employment contract) or who may be covered by care financed by the government or tribe directly.

Modern drug ampoules

Transparency of information is another factor defining a delivery system. Access to information on conditions, treatments, quality, and pricing greatly affects the choice by patients/consumers and, therefore, the incentives of medical professionals. While the US healthcare system has come under fire for lack of openness,[8] new legislation may encourage greater openness. There is a perceived tension between the need for transparency on the one hand and such issues as patient confidentiality and the possible exploitation of information for commercial gain on the other.

[edit]Delivery

See also: Health care, clinic, hospital, and hospice

Provision of medical care is classified into primary, secondary, and tertiary care categories.

Primary care medical services are provided by physicians, physician assistants, nurse practitioners, or other health professionals who have first contact with a patient seeking medical treatment or care. These occur in physician offices, clinics, nursing homes, schools, home visits, and other places close to patients. About 90% of medical visits can be treated by the primary care provider. These include treatment of acute and chronic illnesses, preventive care and health education for all ages and both sexes.

Secondary care medical services are provided by medical specialists in their offices or clinics or at local community hospitals for a patient referred by a primary care provider who first diagnosed or treated the patient. Referrals are made for those patients who required the expertise or procedures performed by specialists. These include both ambulatory care and inpatient services, emergency rooms, intensive care medicine, surgery services,physical therapy, labor and delivery, endoscopy units, diagnostic laboratory and medical imaging services, hospice centers, etc. Some primary care providers may also take care of hospitalized patients and deliver babies in a secondary care setting.

Tertiary care medical services are provided by specialist hospitals or regional centers equipped with diagnostic and treatment facilities not generally available at local hospitals. These include trauma centers, burn treatment centers, advanced neonatology unit services, organ transplants, high-risk pregnancy, radiation oncology, etc.

Modern medical care also depends on information – still delivered in many health care settings on paper records, but increasingly nowadays by electronic means.

[edit]Branches

Working together as an interdisciplinary team, many highly trained health professionals besides medical practitioners are involved in the delivery of modern health care. Examples include: nurses,emergency medical technicians and paramedics, laboratory scientists, pharmacists, physician assistants, podiatrists physiotherapists, respiratory therapists, speech therapists, occupational therapists, radiographers, dietitians, and bioengineers.

The scope and sciences underpinning human medicine overlap many other fields. Dentistry, while considered by some a separate discipline from medicine, is a medical field.

A patient admitted to hospital is usually under the care of a specific team based on their main presenting problem, e.g., the Cardiology team, who then may interact with other specialties, e.g., surgical, radiology, to help diagnose or treat the main problem or any subsequent complications/developments.

Physicians have many specializations and subspecializations into certain branches of medicine, which are listed below. There are variations from country to country regarding which specialties certain subspecialties are in.

The main branches of medicine are:

Basic sciences of medicine; this is what every physician is educated in, and some return to in biomedical research.

Medical specialties

Interdisciplinary fields, where different medical specialties are mixed to function in certain occasions.

[edit]Basic sciences

Anatomy is the study of the physical structure of organisms. In contrast to macroscopic or gross anatomy, cytology and histology are concerned with microscopic structures.

Biochemistry is the study of the chemistry taking place in living organisms, especially the structure and function of their chemical components.

Biomechanics is the study of the structure and function of biological systems by means of the methods of Mechanics.

Biostatistics is the application of statistics to biological fields in the broadest sense. A knowledge of biostatistics is essential in the planning, evaluation, and interpretation of medical research. It is also fundamental to epidemiology and evidence-based medicine.

Biophysics is an interdisciplinary science that uses the methods of physics and physical chemistry to study biological systems.

Cytology is the microscopic study of individual cells.

Louis Pasteur in his laboratory, 1885

Embryology is the study of the early development of organisms.

Endocrinology is the study of hormones and their effect throughout the body of animals.

Epidemiology is the study of the demographics of disease processes, and includes, but is not limited to, the study of epidemics.

Genetics is the study of genes, and their role in biological inheritance.

Histology is the study of the structures of biological tissues by light microscopy, electron microscopy and immunohistochemistry.

Immunology is the study of the immune system, which includes the innate and adaptive immune system in humans, for example.

Medical physics is the study of the applications of physics principles in medicine.

Microbiology is the study of microorganisms, including protozoa, bacteria, fungi, and viruses.

Molecular biology is the study of molecular underpinnings of the process of replication, transcription and translation of the genetic material.

Neuroscience includes those disciplines of science that are related to the study of the nervous system. A main focus of neuroscience is the biology and physiology of the human brain and spinal cord. Some related clinical specialties include neurology, neurosurgery and psychiatry.

Nutrition science (theoretical focus) and dietetics (practical focus) is the study of the relationship of food and drink to health and disease, especially in determining an optimal diet. Medical nutrition therapy is done by dietitians and is prescribed for diabetes, cardiovascular diseases, weight and eatingdisorders, allergies, malnutrition, and neoplastic diseases.

Pathology as a science is the study of disease—the causes, course, progression and resolution thereof.

Pharmacology is the study of drugs and their actions.

Photobiology is the study of the interactions between non-ionizing radiation and living organisms.

Physiology is the study of the normal functioning of the body and the underlying regulatory mechanisms.

Radiobiology is the study of the interactions between ionizing radiation and living organisms.

Toxicology is the study of hazardous effects of drugs and poisons.

[edit]Specialties

Main article: Medical specialty

In the broadest meaning of "medicine", there are many different specialties. In the UK, most specialities will have their own body or college (collectively known as the Royal Colleges, although currently not all use the term "Royal"), which have their own entrance exam. The development of a speciality is often driven by new technology (such as the development of effective anaesthetics) or ways of working (e.g., emergency departments), which leads to the desire to form a unifying body of doctors and thence the prestige of administering their own exam.

Within medical circles, specialities usually fit into one of two broad categories: "Medicine" and "Surgery." "Medicine" refers to the practice of non-operative medicine, and most subspecialties in this area require preliminary training in "Internal Medicine". In the UK, this would traditionally have been evidenced by obtaining the MRCP (An exam allowing Membership of the Royal College of Physicians or the equivalent college in Scotland or Ireland). "Surgery" refers to the practice of operative medicine, and most subspecialties in this area require preliminary training in "General Surgery." (In the UK: Membership of the Royal College of Surgeons of England (MRCS).)There are some specialties of medicine that at the present time do not fit easily into either of these categories, such as radiology, pathology, or anesthesia. Most of these have branched from one or other of the two camps above – for example anaesthesia developed first as a faculty of the Royal College of Surgeons (for which MRCS/FRCS would have been required) before becoming the Royal College of Anaesthetists and membership of the college is by sitting the FRCA (Fellowship of the Royal College of Anesthetists).

[edit]Surgery

Main article: Surgery

Surgeons in an operating room

Surgical specialties employ operative treatment. In addition, surgeons must decide when an operation is necessary, and also treat many non-surgical issues, particularly in the surgical intensive care unit (SICU), where a variety of critical issues arise. Surgeons must also manage pre-operative, post-operative, and potential surgical candidates on the hospital wards. Surgery has many sub-specialties, including general surgery, cardiovascular surgery,colorectal surgery, neurosurgery, maxillofacial surgery, oncologic surgery, orthopedic surgery, otolaryngology, plastic surgery, podiatric surgery,transplant surgery, trauma surgery, urology, vascular surgery, and pediatric surgery. In some centers, anesthesiology is part of the division of surgery (for historical and logistical reasons), although it is not a surgical discipline. Other medical specialties may employ surgical procedures, such asophthalmology and dermatology, but are not considered surgical sub-specialties per se.

Surgical training in the U.S. requires a minimum of five years of residency after medical school. Sub-specialties of surgery often require seven or more years. In addition, fellowships can last an additional one to three years. Because post-residency fellowships can be competitive, many trainees devote two additional years to research. Thus in some cases surgical training will not finish until more than a decade after medical school. Furthermore, surgical training can be very difficult and time consuming.

[edit]'Medicine' as a specialty

Main article: Internal Medicine

Internal medicine is the medical specialty concerned with the diagnosis, management and nonsurgical treatment of unusual or serious diseases, either of one particular organ system or of the body as a whole. According to some sources, an emphasis on internal structures is implied.[9] In North America, specialists in internal medicine are commonly called "internists". Elsewhere, especially in Commonwealth nations, such specialists are often called physicians.[10] These terms, internist or physician (in the narrow sense, common outside North America), generally exclude practitioners of gynecology and obstetrics, pathology, psychiatry, and especially surgery and its subspecialities.

Because their patients are often seriously ill or require complex investigations, internists do much of their work in hospitals. Formerly, many internists were not subspecialized; such general physicians would see any complex nonsurgical problem; this style of practice has become much less common. In modern urban practice, most internists are subspecialists: that is, they generally limit their medical practice to problems of one organ system or to one particular area of medical knowledge. For example, gastroenterologists and nephrologists specialize respectively in diseases of the gut and the kidneys.[11]

In the Commonwealth of Nations and some other countries, specialist pediatricians and geriatricians are also described as specialist physicians (or internists) who have subspecialized by age of patient rather than by organ system. Elsewhere, especially in North America, general pediatrics is often a form of Primary care.

There are many subspecialities (or subdisciplines) of internal medicine:

Cardiology

Critical care medicine

Endocrinology

Gastroenterology

Geriatrics

Haematology

Hepatology

Infectious diseases

Nephrology

Oncology

Pediatrics

Pulmonology/Pneumology/Respirology

Rheumatology

Sleep medicine.

Training in internal medicine (as opposed to surgical training), varies considerably across the world: see the articles on Medical education and Physician for more details. In North America, it requires at least three years of residency training after medical school, which can then be followed by a one to three year fellowship in the subspecialties listed above. In general, resident work hours in medicine are less than those in surgery, averaging about 60 hours per week in the USA. This difference does not apply in the UK where all doctors are now required by law to work less than 48 hours per week on average.

[edit]Diagnostic specialties

Clinical laboratory sciences are the clinical diagnostic services that apply laboratory techniques to diagnosis and management of patients. In the United States, these services are supervised by a pathologist. The personnel that work in these medical laboratory departments are technically trained staff who do not hold medical degrees, but who usually hold an undergraduatemedical technology degree, who actually perform the tests, assays, and procedures needed for providing the specific services. Subspecialties include Transfusion medicine, Cellular pathology,Clinical chemistry, Hematology, Clinical microbiology and Clinical immunology.

Pathology as a medical specialty is the branch of medicine that deals with the study of diseases and the morphologic, physiologic changes produced by them. As a diagnostic specialty, pathology can be considered the basis of modern scientific medical knowledge and plays a large role in evidence-based medicine. Many modern molecular tests such as flow cytometry,polymerase chain reaction (PCR), immunohistochemistry, cytogenetics, gene rearrangements studies and fluorescent in situ hybridization (FISH) fall within the territory of pathology.

Radiology is concerned with imaging of the human body, e.g. by x-rays, x-ray computed tomography, ultrasonography, and nuclear magnetic resonance tomography.

Nuclear medicine is concerned with studying human organ systems by administering radiolabelled substances (radiopharmaceuticals) to the body, which can then be imaged outside the body by a gamma camera or a PET scanner. Each radiopharmaceutical consists of two parts: a tracer that is specific for the function under study (e.g., neurotransmitter pathway, metabolic pathway, blood flow, or other), and a radionuclide (usually either a gamma-emitter or a positron emitter). There is a degree of overlap between nuclear medicine and radiology, as evidenced by the emergence of combined devices such as the PET/CT scanner.

Clinical neurophysiology is concerned with testing the physiology or function of the central and peripheral aspects of the nervous system. These kinds of tests can be divided into recordings of: (1) spontaneous or continuously running electrical activity, or (2) stimulus evoked responses. Subspecialties include Electroencephalography, Electromyography, Evoked potential, Nerve conduction study and Polysomnography. Sometimes these tests are performed by techs without a medical degree, but the interpretation of these tests is done by a medical professional.

[edit]Other major specialties

The followings are some major medical specialties that do not directly fit into any of the above mentioned groups.

Anesthesiology (also known as anaesthetics): concerned with the perioperative management of the surgical patient. The anesthesiologist's role during surgery is to prevent derangement in the vital organs' (i.e. brain, heart, kidneys) functions and postoperative pain. Outside of the operating room, the anesthesiology physician also served the same function in the labor & delivery ward, and some are specialized in critical medicine.

Dermatology is concerned with the skin and its diseases. In the UK, dermatology is a subspecialty of general medicine.

Emergency medicine is concerned with the diagnosis and treatment of acute or life-threatening conditions, including trauma, surgical, medical, pediatric, and psychiatric emergencies.

Family medicine, family practice, general practice or primary care is, in many countries, the first port-of-call for patients with non-emergency medical problems. Family physicians often provide services across a broad range of settings including office based practices, emergency room coverage, inpatient care, and nursing home care.

Obstetrics and gynecology (often abbreviated as OB/GYN (American English) or Obs & Gynae (British English)) are concerned respectively with childbirth and the female reproductive and associated organs. Reproductive medicine and fertility medicine are generally practiced by gynecological specialists.

Medical Genetics is concerned with the diagnosis and management of hereditary disorders.

Neurology is concerned with diseases of the nervous system. In the UK, neurology is a subspecialty of general medicine.

Ophthalmology exclusively concerned with the eye and ocular adnexa, combining conservative and surgical therapy.

Pediatrics (AE) or paediatrics (BE) is devoted to the care of infants, children, and adolescents. Like internal medicine, there are many pediatric subspecialties for specific age ranges, organ systems, disease classes, and sites of care delivery.

Physical medicine and rehabilitation (or physiatry) is concerned with functional improvement after injury, illness, or congenital disorders.

Podiatric medicine study of, diagnosis, and medical treatment of disorders of the foot, ankle, lower limb, hip and lower back.

Psychiatry is the branch of medicine concerned with the bio-psycho-social study of the etiology, diagnosis, treatment and prevention of cognitive, perceptual, emotional and behavioraldisorders. Related non-medical fields include psychotherapy and clinical psychology.

Preventive medicine is the branch of medicine concerned with preventing disease.

Community health or public health is an aspect of health services concerned with threats to the overall health of a community based on population health analysis.

Occupational medicine's principal role is the provision of health advice to organizations and individuals to ensure that the highest standards of health and safety at work can be achieved and maintained.

Aerospace medicine deals with medical problems related to flying and space travel.

[edit]Interdisciplinary fields

Some interdisciplinary sub-specialties of medicine include:

Addiction medicine deals with the treatment of addiction.

Medical ethics deals with ethical and moral principles that apply values and judgments to the practice of medicine.

Biomedical Engineering is a field dealing with the application of engineering principles to medical practice.

Clinical pharmacology is concerned with how systems of therapeutics interact with patients.

Conservation medicine studies the relationship between human and animal health, and environmental conditions. Also known as ecological medicine, environmental medicine, or medical geology.

Disaster medicine deals with medical aspects of emergency preparedness, disaster mitigation and management.

Diving medicine (or hyperbaric medicine) is the prevention and treatment of diving-related problems.

Evolutionary medicine is a perspective on medicine derived through applying evolutionary theory.

Forensic medicine deals with medical questions in legal context, such as determination of the time and cause of death, type of weapon used to inflict trauma, reconstruction of the facial features using remains of deceased (skull)thus aiding identification.

Gender-based medicine studies the biological and physiological differences between the human sexes and how that affects differences in disease.

Hospice and Palliative Medicine is a relatively modern branch of clinical medicine that deals with pain and symptom relief and emotional support in patients with terminal illnesses including cancer and heart failure.

Hospital medicine is the general medical care of hospitalized patients. Physicians whose primary professional focus is hospital medicine are called hospitalists in the USA and Canada. The term Most Responsible Physician (MRP) or attending physician is also used interchangeably to describe this role.

Laser medicine involves the use of lasers in the diagnostics and/or treatment of various conditions.

Medical humanities includes the humanities (literature, philosophy, ethics, history and religion), social science (anthropology, cultural studies, psychology, sociology), and the arts (literature, theater, film, and visual arts) and their application to medical education and practice.

Medical informatics, medical computer science, medical information and eHealth are relatively recent fields that deal with the application of computers and information technology to medicine.

Nosology is the classification of diseases for various purposes.

Nosokinetics is the science/subject of measuring and modelling the process of care in health and social care systems.

Pain management (also called pain medicine, or algiatry) is the medical discipline concerned with the relief of pain.

Pharmacogenomics is a form of individualized medicine.

Podiatric medicine study of, diagnosis, and medical treatment of disorders of the foot, ankle, lower limb, hip and lower back. .

Sexual medicine is concerned with diagnosing, assessing and treating all disorders related to sexuality.

Sports medicine deals with the treatment and prevention and rehabilitation of sports/exercise injuries such as muscle spasms, muscle tears, injuries to ligaments (ligament tears or ruptures) and their repair in athletes, amateur and professional. The team includes specialty physicians and surgeons, athletic trainers, physical therapists, psychiatrists and/or psychologists, coaches, other personnel, and, of course, the athlete.

Therapeutics is the field, more commonly referenced in earlier periods of history, of the various remedies that can be used to treat disease and promote health.[12]

Travel medicine or emporiatrics deals with health problems of international travelers or travelers across highly different environments.

Urgent care focuses on delivery of unscheduled, walk-in care outside of the hospital emergency department for injuries and illnesses that are not severe enough to require care in an emergency department. In some jurisdictions this function is combined with the emergency room.

Veterinary medicine; veterinarians apply similar techniques as physicians to the care of animals.

Wilderness medicine entails the practice of medicine in the wild, where conventional medical facilities may not be available.

Many other health science fields, e.g. dietetics

[edit]Education

Main articles: Medical education and Medical school

Painted by Toulouse-Lautrec in the year of his own death: an examination in the Paris faculty of medicine, 1901

Medical education and training varies around the world. It typically involves entry level education at a university medical school, followed by a period of supervised practice or internship, and/or residency. This can be followed by postgraduate vocational training. A variety of teaching methods have been employed in medical education, still itself a focus of active research. In Canada and the United States of America, a Doctor of Medicine degree, often abbreviated M.D. or a Doctor of Osteopathic Medicine degree, often abbreviated as D.O. and unique to the United States, must be completed in a recognized university.

Many regulatory authorities require continuing medical education, since knowledge, techniques and medical technology continue to evolve at a rapid rate. the means through which doctors upgrade their medical knowledge include medical journals, seminars, conferences and online programs apart form others.

[edit]Medical ethics

Main article: Medical ethics

Medical ethics is a system of moral principles that apply values and judgments to the practice of medicine. As a scholarly discipline, medical ethics encompasses its practical application in clinical settings as well as work on its history, philosophy, theology, and sociology. Six of the values that commonly apply to medical ethics discussions are:

autonomy - the patient has the right to refuse or choose their treatment. (Voluntas aegroti suprema lex.)

beneficence - a practitioner should act in the best interest of the patient. (Salus aegroti suprema lex.)

justice - concerns the distribution of scarce health resources, and the decision of who gets what treatment (fairness and equality).

non-maleficence - "first, do no harm" (primum non nocere).

respect for persons - the patient (and the person treating the patient) have the right to be treated with dignity.

truthfulness and honesty - the concept of informed consent has increased in importance since the historical events of the Doctors' Trial of the Nuremberg trials and Tuskegee syphilis experiment.

Values such as these do not give answers as to how to handle a particular situation, but provide a useful framework for understanding conflicts. When moral values are in conflict, the result may be an ethical dilemma or crisis. Sometimes, no good solution to a dilemma in medical ethics exists, and occasionally, the values of the medical community (i.e., the hospital and its staff) conflict with the values of the individual patient, family, or larger non-medical community. Conflicts can also arise between health care providers, or among family members. Some argue for example, that the principles of autonomy and beneficence clash when patients refuse blood transfusions, considering them life-saving; and truth-telling was not emphasized to a large extent before the HIV era.

[edit]Legal controls

In most countries, it is a legal requirement for a medical doctor to be licensed or registered. In general, this entails a medical degree from a university and accreditation by a medical board or an equivalent national organization, which may ask the applicant to pass exams. This restricts the considerable legal authority of the medical profession to physicians that are trained and qualified by national standards. It is also intended as an assurance to patients and as a safeguard against charlatans that practice inadequate medicine for personal gain. While the laws generally require medical doctors to be trained in "evidence based", Western, or Hippocratic Medicine, they are not intended to discourage different paradigms of health.

In the European Union, the profession of doctor of medicine is regulated. A profession is said to be regulated when access and exercise is subject to the possession of a specific professional qualification. The regulated professions database contains a list of regulated professions for doctor of medicine in the EU member states, EEA countries and Switzerland. This list is covered by the Directive 2005/36/EC .

Doctors who are negligent or intentionally harmful in their care of patients can face charges of medical malpractice and be subject to civil, criminal, or professional sanctions.

[edit]Criticism of modern medicine

According to Paul Farmer, the main problem for modern medicine is lack of access in poor regions. There is an "outcome gap" between the rich and poor that is most noticeable with expensive-to-treat diseases like AIDS and tuberculosis. The majority of medical resources and therapies are concentrated in the rich, low-incidence regions such as the West. On the other hand, countries in the developing world have high rates of HIV but lack the resources to treat them.[13]

Medical errors and overmedication are also the focus of complaints and negative coverage. Practitioners of human factors engineering believe that there is much that medicine may usefully gain by emulating concepts in aviation safety, where it is recognized that it is dangerous to place too much responsibility on one "superhuman" individual and expect him or her not to make errors. Reporting systems and checking mechanisms are becoming more common in identifying sources of error and improving practice. Clinical versus statistical, algorithmic diagnostic methods were famously examined in psychiatric practice in a 1954 book by Paul E. Meehl, which found statistical methods superior.[14] A 2000 meta-analysis comparing these methods in both psychology and medicine found that statistical or "mechanical" diagnostic methods were, in general, although not always, superior.[14]

Disparities in quality of care given among local demographics are often an additional cause of controversy.[15] For example, elderly mentally ill patients received poorer care during hospitalization in a 2008 study.[16] Rural poor African-American men were used in an infamous study of syphilis that denied them basic medical care.

[edit]Honors and awards

Main article: Nobel prize in Physiology or Medicine

The highest honor awarded in medicine is the Nobel Prize in Medicine, awarded since 1901 by the Nobel Assembly at Karolinska Institutet.

[edit]History

Main article: Timeline of medicine and medical technology

[edit]Ancient world

Statuette of ancient Egyptian physician Imhotep, the first physician from antiquity known by name.

Prehistoric medicine incorporated plants (herbalism), animal parts and minerals. In many cases these materials were used ritually as magical substances by priests, shamans, or medicine men. Well-known spiritual systems include animism (the notion of inanimate objects having spirits), spiritualism (an appeal to gods or communion with ancestor spirits); shamanism (the vesting of an individual with mystic powers); and divination (magically obtaining the truth). The field of medical anthropology examines the ways in which culture and society are organized around or impacted by issues of health, health care and related issues.

An ancient Greek patient gets medical treatment: this aryballos (circa480–470 BCE, now in Paris's Louvre Museum) probably contained healing oil

The Greek physician Hippocrates(ca. 460 BCE – ca. 370 BCE), considered the father of medicine.[17][18]

Early records on medicine have been discovered from ancient Egyptian medicine, Babylonian medicine, Ayurvedicmedicine (in the Indian subcontinent), classical Chinese medicine (predecessor to the modern traditional Chinese Medicine), and ancient Greek medicine and Roman medicine. The Egyptian Imhotep (3rd millennium BC) is the first physician in history known by name. Earliest records of dedicated hospitals come from Mihintale in Sri Lanka where evidence of dedicated medicinal treatment facilities for patients are found.[19][20] The Indian surgeon Sushrutadescribed numerous surgical operations, including the earliest forms of plastic surgery.[21][dubious – discuss][22][23]

The Greek physician Hippocrates, the "father of medicine",[17][18] laid the foundation for a rational approach to medicine. Hippocrates introduced the Hippocratic Oath for physicians, which is still relevant and in use today, and was the first to categorize illnesses as acute, chronic, endemic and epidemic, and use terms such as, "exacerbation, relapse, resolution, crisis, paroxysm, peak, and convalescence".[24][25]

The Greek physician Galen was also one of the greatest surgeons of the ancient world and performed many audacious operations, including brain and eye surgeries. After the fall of the Western Roman Empire and the onset of the Early Middle Ages, the Greek tradition of medicine went into decline in Western Europe, although it continued uninterrupted in the Eastern Roman (Byzantine) Empire.

Most of our knowledge of ancient Hebrew medicine during the 1st millennium BC comes from the Torah, i.e. the Five Books of Moses, which contain various health related laws and rituals. The Hebrew contribution to the development of modern medicine started in the Byzantine Era, with the physicianAsaph the Jew.[26]

[edit]Middle ages

After 750 CE, the Muslim world had the works of Hippocrates, Galen and Sushruta translated into Arabic, and Islamic physicians engaged in some significant medical research. Notable Islamic medical pioneers include the polymath, Avicenna, who, along with Imhotep and Hippocrates, has also been called the "father of medicine".[27][28] He wrote The Canon of Medicine, considered one of the most famous books in the history of medicine.[29] Others include Abulcasis,[30] Avenzoar,[31] Ibn al-Nafis,[32] and Averroes.[33] Rhazes[34] was one of first to question the Greek theory of humorism, which nevertheless remained influential in both medieval Western and medieval Islamic medicine.[35] The Islamic Bimaristan hospitals were an early example ofpublic hospitals.[36][37]

However, the fourteenth and fifteenth century Black Death was just as devastating to the Middle East as to Europe, and it has even been argued that Western Europe was generally more effective in recovering from the pandemic than the Middle East.[38] In the early modern period, important early figures in medicine and anatomy emerged in Europe, including Gabriele Falloppio and William Harvey.

The major shift in medical thinking was the gradual rejection, especially during the Black Death in the 14th and 15th centuries, of what may be called the 'traditional authority' approach to science and medicine. This was the notion that because some prominent person in the past said something must be so, then that was the way it was, and anything one observed to the contrary was an anomaly (which was paralleled by a similar shift in European society in general – see Copernicus's rejection of Ptolemy's theories on astronomy). Physicians like Vesalius improved upon or disproved some of the theories from the past. The main tomes used both by medicine students and expert physicians were Materia Medica and Pharmacopoeia.

Andreas Vesalius was an author of one of the most influential books on human anatomy, De humani corporis fabrica.[39] French surgeon Ambroise Paré is considered as one of the fathers ofsurgery. Bacteria and microorganisms were first observed with a microscope by Antonie van Leeuwenhoek in 1676, initiating the scientific field microbiology.[40] Independently from Ibn al-Nafis,Michael Servetus rediscovered the pulmonary circulation, but this discovery did not reach the public cause it was written down for the first time in the "Manuscript of Paris"[41] in 1546, and later published in the theological work which he paid with his life in 1553. Later this was described by Renaldus Columbus and Andrea Cesalpino. Partly based on the works by the Italian surgeon and anatomist Renaldus Columbus the English physician William Harvey described the circulatory system.[42] Herman Boerhaave is sometimes referred to as a "father of physiology" due to his exemplary teaching in Leiden and textbook 'Institutiones medicae' (1708). It is said that the 17th century French physician Pierre Fauchard started dentistry science as we know it today, and he has been named "the father of modern dentistry".[43]

[edit]Modern

Paul-Louis Simond injecting a plague vaccine in Karachi, 1898

Veterinary medicine was for the first time truly separated from human medicine in 1761, when the French veterinarian Claude Bourgelat founded the world's first veterinary school in Lyon, France. Before this, medical doctors treated both humans and other animals.

Modern scientific biomedical research (where results are testable and reproducible) began to replace early Western traditions based on herbalism, the Greek "four humours" and other such pre-modern notions. The modern era really began with Edward Jenner's discovery of the smallpox vaccine at the end of the 18th century (inspired by the method of inoculation earlier practiced in Asia), Robert Koch's discoveries around 1880 of the transmission of disease by bacteria, and then the discovery of antibiotics around 1900.

The post-18th century modernity period brought more groundbreaking researchers from Europe. From Germany and Austria, doctors Rudolf Virchow,Wilhelm Conrad Röntgen, Karl Landsteiner and Otto Loewi made notable contributions. In the United Kingdom, Alexander Fleming, Joseph Lister,Francis Crick and Florence Nightingale are considered important. Spanish doctor Santiago Ramón y Cajal is considered the father of modernneuroscience.

From New Zealand and Australia came Maurice Wilkins, Howard Florey, and Frank Macfarlane Burnet.

In the United States, William Williams Keen, William Coley, James D. Watson, Italy (Salvador Luria), Switzerland (Alexandre Yersin), Japan (Kitasato Shibasaburō), and France (Jean-Martin Charcot, Claude Bernard, Paul Broca and others did significant work). Russian Nikolai Korotkov also did significant work, as did Sir William Osler and Harvey Cushing.

Alexander Fleming's discovery of penicillin in September 1928 marks the start of modern antibiotics.

As science and technology developed, medicine became more reliant upon medications. Throughout history and in Europe right until the late 18th century, not only animal and plant products were used as medicine, but also human body parts and fluids.[44] Pharmacology developed from herbalismand many drugs are still derived from plants (atropine, ephedrine, warfarin, aspirin, digoxin, vinca alkaloids, taxol, hyoscine, etc.). Vaccines were discovered by Edward Jenner and Louis Pasteur.

The first antibiotic was arsphenamine / Salvarsan discovered by Paul Ehrlich in 1908 after he observed that bacteria took up toxic dyes that human cells did not. The first major class of antibiotics was the sulfa drugs, derived by German chemists originally from azo dyes.

Pharmacology has become increasingly sophisticated; modern biotechnology allows drugs targeted towards specific physiological processes to be developed, sometimes designed for compatibility with the body to reduce side-effects. Genomics and knowledge of human genetics is having some influence on medicine, as the causative genes of most monogenic genetic disorders have now been identified, and the development of techniques inmolecular biology and genetics are influencing medical technology, practice and decision-making.

Evidence-based medicine is a contemporary movement to establish the most effective algorithms of practice (ways of doing things) through the use ofsystematic reviews and meta-analysis. The movement is facilitated by modern global information science, which allows as much of the available evidence as possible to be collected and analyzed according to standard protocols that are then disseminated to healthcare providers. The Cochrane Collaboration leads this movement. A 2001 review of 160 Cochrane systematic reviews revealed that, according to two readers, 21.3% of the reviews concluded insufficient evidence, 20% concluded evidence of no effect, and 22.5% concluded positive effect.[45]

[edit]Patron saints

There are a number of patron saints for physicians, the most important of whom are Saint Luke the Evangelist the physician and disciple of Christ, Saints Cosmas and Damian (3rd-century physicians from Syria), and Saint Pantaleon (4th-century physician from Nicomedia). Archangel Raphael is also considered a patron saint of physicians. In India and in Hinduism, Dhanavantari, a form of Lord Vishnu and "Vaidyanatha" meaning 'Lord of Medicine', a form of Lord Shiva are the patron deities of medicine.

The patron saints for surgeons are Saint Luke the Evangelist, the physician and disciple of Christ, Saints Cosmas and Damian (3rd-century physicians from Syria), Saint Quentin (3rd-century saint from France), Saint Foillan (7th-century saint from Ireland), and Saint Roch (14th-century saint from France).