Acute inflammation 1 Flashcards
(28 cards)
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?
- acute
- chronic
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?
oedema
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?
- 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
