Session 7: Introduction to Inflammation

Session 7: Introduction to Inflammation

• Felician Sikujua (MD)

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Learning tasks

Learning tasks

At the end of this session, students are expected to be able to:

Define inflammation.

Explain the role of inflammation.

Explain basic features of inflammation.

Identify of steps of inflammatory response.

Identify causes of inflammation.

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Definition

Definition

The term is derived from the Latin "inflammare" meaning to burn.

Inflammation is an ability of vascularised living tissue to respond to any noxious agent or injury.

It is a protective response intended to eliminate the initial cause of cell injury as well as the necrotic cells and tissues resulting from the original insult.

It is a complex reaction which involves many other systemic changes despite of what is observed locally.

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Roles of Inflammation

Roles of Inflammation

Inflammation is fundamentally destined to localize and eliminate the causative agent and to limit tissue injury.

The survival of all organisms requires that they eliminate foreign invaders, such as infectious agents, and damaged tissues.

These functions are mediated by a complex host response called inflammation.

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Roles of Inflammation cont…

Roles of Inflammation cont…

Inflammation accomplishes its protective mission by first diluting, destroying, or otherwise neutralizing harmful agents (e.g., microbes, toxins).

It then sets into motion the events that eventually heal and repair the sites of injury.

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Roles of Inflammation cont…

Roles of Inflammation cont…

Without inflammation

Infections would go unchecked.

Wounds would never heal.

Injured tissues would remain permanent festering (e.g in suppurative- pus forming sores).

In the context of infections, inflammation is one component of a protective response that refer to as innate immunity.

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Activity: Brainstorming

Activity: Brainstorming

How can inflammation be harmful to normal tissue?

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Inflammation can be harmful

Inflammation can be harmful

The inflammatory reactions and the subsequent repair process can themselves cause considerable harm.

The components of the inflammatory reaction that destroy and eliminate microbes and dead tissues are also capable of injuring normal tissues.

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Inflammation can be harmful cont…

Inflammation can be harmful cont…

The damage may even become the dominant feature if the inflammatory reaction is:

Very strong (e.g., when the infection is severe)

Prolonged (e.g., when the eliciting agent resists eradication)

Inappropriate (e.g., when it is directed against self-antigens in autoimmune diseases or against usually harmless environmental antigens (e.g., in allergic disorders).

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Basic features of Inflammation

Basic features of Inflammation

Inflammation can be acute or chronic.

Inflammation is induced by chemical mediators that are produced by host cells in response to injurious stimuli.

The external manifestations of inflammation, often called its cardinal signs of inflammation.

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Basic features of Inflammation cont…

Basic features of Inflammation cont…

Inflammation is normally controlled and self-limited.

Inflammation is a defensive host response to foreign invaders and necrotic tissue, but it is itself capable of causing tissue damage.

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Steps of Inflammatory response

Steps of Inflammatory response

Recognition of the injurious agent.

Recruitment of leukocytes.

Removal of the agent.

Regulation (control) of the inflammatory response.

Resolution (repair).

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Causes of Inflammation

Causes of Inflammation

Physical agents – mechanical injuries (trauma), alteration in temperatures and pressure, radiation injuries.

Chemical agents – including the ever increasing lists of drugs and toxins (organic and inorganic poisons)

Biologic agents (infectious agents) – bacteria, viruses, fungi, parasites and their toxins.

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Causes of Inflammation cont…

Causes of Inflammation cont…

• Immunologic disorders – hypersensitivity reactions, autoimmunity, immunodeficiency states.
• Genetic/metabolic disorders – examples gout, diabetes mellitus.

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Types of Inflammation

Types of Inflammation

Depending on the different capacity of the host and duration of response and histologic appearances, inflammation can be classified into:

Acute inflammation.

Chronic inflammation.

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Nomenclature

Nomenclature

The presence of inflammation is indicated by addition of suffix 'itis' to the name of organ involved.

If it is Acute add the word acute.

Acute bronchitis.

Acute laryngitis.

If it is chronic add the word chronic.

Chronic tonsillitis

Chronic cervicitis.

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Nomenclature cont…

Nomenclature cont…

However, like any rule, it has its own exceptions examples pneumonia, typhoid fever.

Those diseases do not end with suffix 'itis' but they are inflammatory.

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Key points

Key points

It is a defensive local response of the living mammalian tissues to injury due to an agent

The goal of the inflammatory reaction is to bring leukocytes and plasma proteins to the site of injury.

Cardinal signs of inflammation are commonly seen in Acute inflammation.

Acute and chronic inflammation can coexist.

Inflammation can also cause tissue damage when an inflammatory reaction is very strong, prolonged or inappropriate.

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Review questions

Review questions

Why is inflammatory process important?

Explain how inflammation achieves its protective response.

List steps involved in inflammatory response.

What are the causes of inflammation?

List five examples of inflammatory condition not end with suffix 'itis'.

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References

References

Bezabeh M.; Tesfaye A.; Ergicho B. et al (2004): General pathology lecture notes for Health Sciences students. Ethiopia Public Health Training Initiative. Pg. 24.

Kumar V.; Abbas A. K.; Aster J. C.;(2013): Robbins and Contran Pathologic Basis of Disease (9th Ed.) Elsevier Saunders, China. Pg. 30 – 31.

Mohan H.;(2010): Text book of Pathology (6th Ed.) Jaypee Brothers Medical Publishers, India . Pg. 130.

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