4. Acute inflammation Flashcards
What are the causes of acute inflammation?
- tissue death (ischaemia, trauma, toxins, chemical insults, thermal injury, radiation)
- infection (especially bacterial, pyogenic)
Define pyogenic
Pus forming
Define suppuration
The formation of pus
What is pus?
An accumulation of acute inflammatory cells, dead cells, bacteria etc.
What comes after acute inflammation?
Either
- healing by regeneration
- healing by repair
or - chronic inflammation
When does healing by regeneration occur?
After acute inflammation, when the cells can regrow
When does healing by repair occur?
After acute inflammation, when the cells canon regrow
When does chronic inflammation occur following acute inflammation?
After acute inflammation, when the damaging agent persists
What are the purposes of acute inflammation?
- clear away dead tissues
- locally protect from infection
- allow access of immune system components
What are the 4 cardinal signs of inflammation?
- calor (=heat)
- rubor (=redness)
- dolor (=pain)
- tumor (=swelling)
In addition to the main 4 cardinal signs of inflammation, what is the extra one?
Disturbance of function
Why does rubor (redness) and calor (heat) occur in inflammation?
Due to vascular dilation
Why does swelling occur in inflammation?
Due to inflammatory exudate into surrounding tissues
Acute inflammation will look different in different organs. Name 4 different types of acute inflammation.
- serous
- fibrinous
- purulent
- pseudomembranous
What occurs in serous inflammation?
Fluid accumulates in cavity
What occurs in fibrinous inflammation?
Precipitation of fibrin
What occurs in purulent inflammation?
Formation of pus
This is very common
What are 3 components of the acute inflammatory reaction?
- vascular reaction
- exudative reaction
- cellular reaction
What is the vascular reaction? (a stage of acute inflammatory response)
Dilatation of blood vessels (=rubor), changes in flow
What is the exudative reaction? (a stage of acute inflammatory response)
Vessels become leaky, formation of inflammatory exudate (=tumor)
What is the cellular reaction? (a stage of acute inflammatory response)
Migration of inflammatory cells out of vessels
Define pyrexia
High temperature due to inflammation
How can the severity of acute inflammatory response in a patient be quantified?
- pyrexia
- acute phase reaction
Give an example of a protein that is measured in acute phase reaction?
C-reactive protein
ESR (erythrocyte sedimentation rate)
What is the acute phase reaction?
Systemic and metabolic changes that occur within hours of an inflammatory stimulus. - acute phase proteins.
Describe the vascular reaction?
Microvascular dilation causes an increase in flow and then flow eventually deceases as the vessels become leaky
What causes increased permeability of vessels?
Mediated =
histamine bradykinin NO leukotriene B4 complement components
Non-mediated =
direct damage to endothelium eg. toxins, physical agents
How can we interfere with increased vascular permeability?
Drugs can affect the mediators which cause mediated increased permeability
What happens in a capillary if there is a greater hydrostatic pressure?
Fluid is pushed out of the capillaries
What happens in a capillary if there is a greater oncotic pressure?
Fluid will enter the capillaries
At the arterial end of a capillary, is hydrostatic or oncotic pressure higher?
Hydrostatic pressure > oncotic pressure at the ARTERIAL end
What does acute inflammatory exudate consist of?
Protein rich (50g/l)
- immunoglobins
- fibrinogen
What are the benefits of acute inflammatory exudate?
constantly turning over
- dilution of noxious agents
- transport to lymph nodes
- supply of nutrients, O2
- spread of drugs
- spread of antibodies
- spread of inflammatory mediators
What is pericarditis?
Inflammation of the pericardium of the heart
What do you see in pericarditis?
A friable shaggy covering of the heart rather than being smooth and shiny.
This is due to fibrinous inflammation (the shaggy material is precipitated fibrin from the inflammatory exudate)
What happens during the cellular reaction?
- accumulation of neutrophils in the extracellular space (neutrophils are normally present in the blood but migrate into the extracellular space in infection)
- in severe cases, accumulation of neutrophils, cellular debris and bacteria forms pus
What do you see in acute meningitis caused by a pyogenic bacterial infection?
Rather than being clear and shiny, the arachnoid covering over the cerebellum is cloudy because of the cell rich exudate in the subarachnoid space (pus)
What type of cells are in the subarachnoid space in acute bacterial meningitis?
Neutrophil polymorphs, these are characteristic of acute inflammation
How would the alveoli feel in the case of bronchopneumonia?
It would feel solid compared to the surrounding lung as the alveoli are filled with the acute inflammatory exudate rather than air
What are the main characteristics of neutrophils?
- produced in the bone marrow
- commonest white cell in the blood
- increase in acute inflammation
- motile, amoeboid, can move into tissues
- directional chemotaxis
- short lifespan (hours in tissues)
- phagocytic, microbiocidal
Where are neutrophils produced?
In the bone marrow
What is the most common white cell in the blood?
Neutrophils
Do neutrophils have a long or short lifespan?
Short.
hours in tissues
What are the stages as neutrophils flow in the blood during inflammatory response?
- margination
- rolling - adhesion (pavementing - can see this microscopically)
- migration (RBC diapedesis)
- chemotaxis
Where are the mediators of acute inflammation derived?
Cell derived or plasma derived
List the plasma derived mediators of acute inflammation
- kinin system
- clotting pathway
- thrombolytic pathway
- complement pathway
What are the cell derived mediators of acute inflammation?
Stored = histamine Synthesised = prostaglandins leukotrienes PAF cytokines (IL1, IL8, TNFa) NO chemokines
Why are the mediators of acute inflammation important to know about?
We can interfere with them with drugs
What contributes to laboratory assessment of inflammation?
- full blood count
- erythrocyte sedimentation rate
- acute phase reaction eg. C-reactive protein
What diseases are caused by the inflammatory pathway going wrong?
- systemic inflammatory response syndrome
- acute (adult) respiratory distress syndrome
- chronic granulomatous disease of childhood
- hereditary angio-oedema
- amyloidosis
What is resolution?
After acute inflammation when there is minimal tissue damage
What is fibrosis?
After acute inflammation when these is some tissue damage
What happens after acute inflammation when there is marked neutrophil reaction with tissue damage?
Suppuration - abscess
What may happen following acute inflammation?
- resolution
- fibrosis
- suppuration - abscess
- chronic inflammation
