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what is inflammation?

local physiological response to tissue injury


what does the inflammatory response affect?

-a complex reaction in vascularised connective tissue
• Reaction of blood vessels which leads to accumulation of fluid and leucocytes in extravascular tissues


what does inflammation serve to do?

- to destroy, dilute or wall off the injurious agent
•The inflammatory response is closely intertwined with the process of repair


what type of response is inflammation?

protective response


what would happen in the absence of inflammation?

-Wounds and injured organs would never heal
- Infections would go unchecked


in what ways can inflammation and repair be potentially harmful?

-Life-threatening hypersensitivity reactions
- Chronic inflammatory diseases eg rheumatoid arthritis and Crohn’s disease
-Repair by fibrosis may lead to problems such as disfiguring scars


what are the two types of inflammation?



what is acute inflammation?

the initial rapid and often short-lived series of tissue reactions to injury


what is chronic inflammation?

the subsequent and often prolonged tissue reactions following the initial response


what are the 5 principal causes of acute inflammation?

1) Infections- viruses
2) Hypersensitivity- excessive/inappropriate immune reaction which damages tissue)
3)physical agents- trauma
4)Irritant and corrosive chemicals - acid
5) Foreign bodies- dirt


what are the physical characteristics of inflammation?

1) Redness (rubor)- dilation of small blood vessels
2) Heat (calor) -increased blood flow
3) Swelling - accumulation of fluid in the extravascular space
4) pain (dolor) -stretching and distortion of tissues caused by increased fluid. Various chemical mediators, including bradykinin are known to produce pain
5) Loss of function- movement is inhibited by pain


what are processes of involved in initial rapid reaction of tissue?

1) i) vasodilatation
ii) Increased permeability of blood vessels
2) exudative and cellular phase


what happens during vasodilatation?

Results in increased blood flow thus heat and redness


what happens during increased permeability of blood vessels?

• Small blood vessels are lined by a single layer of endothelial cells
• The walls of small vessels act as a microfilter
• Oxygen, carbon dioxide and some nutrients transfer across the wall by diffusion
• The main transfer of fluid and solutes is by ultrafiltration as described by Starling


what happens during increased vascular permeability -the formation of endothelial gaps in venules?

• Increased vascular permeability is brought about
by chemical mediators including histamine, bradykinin
• Leakage of fluid is confined to POST CAPILLARY VENULES • Gaps in venules are largely intercellular
• Endothelial cells contain contractile proteins, when stimulated by chemical mediators they pull open transient pores
• Endothelial cells are NOT damaged in this process


what are the causes of increased vascular permeability?

-Immediate transient -->chemical mediators e.g. histamine
-Immediate sustained
--> severe direct vascular injury
-delayed prolonged
--> endothelial cell injury e.g. X-rays


what is the net increase in extravascular fluid called?



what is the fluid exudate?

• Proteins including immunoglobulins, important in destruction of invading organisms
• Fibrinogen  Fibrin on contact with the extracellular matrix (ECM), hence acutely inflamed organ surfaces commonly covered by fibrin
• Exudate is continually being removed by the lymphatics and replaced by new exudate


what is the cellular component?

The diagnostic feature of acute inflammation is neutrophil accumulation in the extracellular space


what is a neutrophil?

Leukocyte - white blood cell


what are the functions of neutrophils?

• Kill microorganisms
• Ingest offending agents
• Degrade necrotic tissue
• Produce chemical mediators
• Produce toxic oxygen radicals
• Produce tissue damaging enzymes


How does a neutrophil reach the site of an inflammatory stimulus?

1. Margination-Loss of intravascular fluid and increased plasma viscosity slows flow allowing neutrophils to flow in the plasmatic zone (ONLY in venules)

2)Adhesion-Increased neutrophil adhesion results from interaction between adhesion molecules on its surface and the endothelial surface

3) Transendothelial migration- neutrophils insert pseudopodia into the junctions between endothelial cells. They then cross through the basement membrane and into the extravascular space


How do neutrophils find the site of the Inflammatory stimulus?

chemotaxis - locomotion orientated along a chemical gradient


what are compounds chemotactic for neutrophils ?

• Bacterial products
• Complement components
• Cytokines
• Products produced by neutrophils themselves


what are endogenous chemical mediators ?

chemicals that drive the process of inflammation and cause :
1. Vasodilatation
2. Emigration of neutrophils
3. Chemotaxis
4. Increased vascular permeability
5. Itching and pain


what are 3 examples of a chemical mediators?

-lysosomal compounds


what are the 4 enzymatic cascade systems in plasma?

1. Complement system
2. Coagulation system 3. Kinin system
4. Fibrinolytic system


what breaks down blood clots?