inflammation

1 a response of body tissues to injury or irritation; characterized by pain and swelling and redness and heat [syn: redness, rubor]

2 the state of being emotionally aroused and worked up; "his face was flushed with excitement and his hands trembled"; "he tried to calm those who were in a state of extreme inflammation" [syn: excitement, excitation, fervor, fervour]

3 arousal to violent emotion [syn: inflaming]

4 the act of setting on fire or catching fire [syn: ignition, firing, lighting, kindling]

English

Pronunciation

• Rhymes: -eɪʃǝn

Noun

1. The act of inflaming, kindling, or setting on fire; also, the state of being inflamed.
2. A morbid condition of any part of the body, consisting in congestion of the blood vessels, with obstruction of the blood current, and growth of morbid tissue. It is manifested outwardly by redness and swelling, attended with heat and pain.
3. Violent excitement; heat; passion; animosity; turbulence; as, an inflammation of the mind, of the body politic, or of parties.

Related terms

• infection

Translations

Inflammation (Latin, inflammatio, to set on fire) is the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. It is a protective attempt by the organism to remove the injurious stimuli as well as initiate the healing process for the tissue. Inflammation is not a synonym for infection. Even in cases where inflammation is caused by infection it is incorrect to use the terms as synonyms: infection is caused by an exogenous pathogen, while inflammation is the response of the organism to the pathogen.

In the absence of inflammation, wounds and infections would never heal and progressive destruction of the tissue would compromise the survival of the organism. However, inflammation which runs unchecked can also lead to a host of diseases, such as hay fever, atherosclerosis, and rheumatoid arthritis. It is for this reason that inflammation is normally tightly regulated by the body.

Inflammation can be classified as either acute or chronic. Acute inflammation is the initial response of the body to harmful stimuli and is achieved by the increased movement of plasma and leukocytes from the blood into the injured tissues. A cascade of biochemical events propagates and matures the inflammatory response, involving the local vascular system, the immune system, and various cells within the injured tissue. Prolonged inflammation, known as chronic inflammation, leads to a progressive shift in the type of cells which are present at the site of inflammation and is characterised by simultaneous destruction and healing of the tissue from the inflammatory process.

Causes

• Burns
• Chemical irritants
• Frostbite
• Toxins
• Infection by pathogens
• Necrosis
• Physical injury, blunt or penetrating
• Immune reactions due to hypersensitivity
• Ionizing radiation
• Foreign bodies, including splinters and dirt

Types

Acute inflammation

Acute inflammation is a short-term process which is characterized by the classic signs of inflammation - swelling, redness, pain, heat, and loss of function - due to the infiltration of the tissues by plasma and leukocytes. It occurs as long as the injurious stimulus is present and ceases once the stimulus has been removed, broken down, or walled off by scarring (fibrosis). The first four characteristics have been known since ancient times and are attributed to Celsus. Loss of function was added to the definition of inflammation by Virchow in the 19th century (1870).

The process of acute inflammation is initiated by the blood vessels local to the injured tissue, which alter to allow the exudation of plasma proteins and leukocytes into the surrounding tissue. The increased flow of fluid into the tissue causes the characteristic swelling associated with inflammation since the lymphatic system doesn't have the capacity to compensate for it, and the increased blood flow to the area causes the reddened colour and increased heat. The blood vessels also alter to permit the extravasation of leukocytes through the endothelium and basement membrane constituting the blood vessel. Once in the tissue, the cells migrate along a chemotactic gradient to reach the site of injury, where they can attempt to remove the stimulus and repair the tissue.

Meanwhile, several biochemical cascade systems, consisting of chemicals known as plasma-derived inflammatory mediators, act in parallel to propagate and mature the inflammatory response. These include the complement system, coagulation system and fibrinolysis system.

Finally, down-regulation of the inflammatory response concludes acute inflammation. Removal of the injurious stimuli halts the response of the inflammatory mechanisms, which require constant stimulation to propagate the process. Additionally, many inflammatory mediators have short half lives and are quickly degraded in the tissue, helping to quickly cease the inflammatory response once the stimulus has been removed. and anti-inflammatory drugs work specifically by inhibiting normal inflammatory components.

Cancer

Inflammation orchestrates the microenvironment around tumours, contributing to proliferation, survival and migration. Cancer cells use selectins, chemokines and their receptors for invasion, migration and metastasis. On the other hand, many cells of the immune system contribute to cancer immunology, suppressing cancer.

Termination

The inflammatory response must be actively terminated when no longer needed to prevent unnecessary "bystander" damage to tissues.|30px|30px|Charles Serhan}}

Systemic effects

An organism can escape the confines of the immediate tissue via the circulatory system or lymphatic system, where it may spread to other parts of the body. If an organism is not contained by the actions of acute inflammation it may gain access to the lymphatic system via nearby lymph vessels. An infection of the lymph vessels is known as lymphangitis, and infection of a lymph node is known as lymphadenitis. A pathogen can gain access to the bloodstream through lymphatic drainage into the circulatory system.

When inflammation overwhelms the host, systemic inflammatory response syndrome is diagnosed. When it is due to infection, the term sepsis is applied, with bacteremia being applied specifically for bacterial sepsis and viremia specifically to viral sepsis. Vasodilation and organ dysfunction are serious problems associated with widespread infection that may lead to septic shock and death.

Acute-phase proteins

Inflammation also induces high systemic levels of acute-phase proteins. In acute inflammation, these proteins prove beneficial, however in chronic inflammation they can contribute to amyloidosis During clinical studies, inflammatory-related molecule levels were reduced and increased levels of anti-inflammatory molecules were seen within four weeks after patients began a very low calorie diet. The association of systemic inflammation with insulin resistance and atherosclerosis is the subject of intense research.

Outcomes

The outcome in a particular circumstance will be determined by the tissue in which the injury has occurred and the injurious agent that is causing it. There are three possible outcomes to inflammation:

1. ResolutionThe complete restoration of the inflamed tissue back to a normal status. Inflammatory measures such as vasodilation, chemical production, and leukocyte infiltration cease, and damaged parenchymal cells regenerate. In situations where limited or short lived inflammation has occurred this is usually the outcome.
2. FibrosisLarge amounts of tissue destruction, or damage in tissues unable to regenerate, can not be regenerated completely by the body. Fibrous scarring occurs in these areas of damage, forming a scar composed primarily of collagen. The scar will not contain any specialized structures, such as parenchymal cells, hence functional impairment may occur.
3. Abscess FormationA cavity is formed containing pus, an opaque liquid containing dead white blood cells and bacteria with general debris from destroyed cells.
4. Chronic inflammationIn acute inflammation, if the injurious agent persists then chronic inflammation will ensue. This process, marked by inflammation lasting many days, months or even years, may lead to the formation of a chronic wound. Chronic inflammation is characterised by the dominating presence of macrophages in the injured tissue. These cells are powerful defensive agents of the body, but the toxins they release (including reactive oxygen species) are injurious to the organism's own tissues as well as invading agents. Consequently, chronic inflammation is almost always accompanied by tissue destruction.

Examples

Inflammation is usually indicated by adding the suffix "-itis", as shown below. However, some conditions such as asthma and pneumonia do not follow this convention. More examples are available at list of types of inflammation.

Image:Acute_Appendicitis.jpg|Acute appendicitis dermatitis Image:Streptococcus pneumoniae meningitis, gross pathology 33 lores.jpg|Acute infective meningitis tonsillitis

See also

• Anaphylatoxin
• Anti-inflammatories
• Healing
• Interleukin
• Lipoxin
• Substance P

References

External links

• What You Need to Know About Inflammation at Cleveland Clinic
• Anti-Inflammatory Diet - Foods and Inflammation at About.com

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