Acute Inflammation Flashcards
What is acute inflammation?
Acute inflammation is a dynamic homeostatic response which maintains the integrity of the organism. It involves a series of protective mechanisms that occur in response to injury.
What are the 5 cardinal signs of inflammation?
- Rubor- redness
- Calor- heat
- Tumour- swelling
- Dolor- pain
- Loss of function
What can the cardinal signs of inflammation be explained by?
The sequence of pathological events taking place.
What are the aetiologies of inflammation?
Infection (bacteria/viruses/parasites/fungi etc)
Trauma (even sterile surgery)
Dead tissue (cell necrosis irritates adjacent tissue)
Hypersensitivity
Where does acute inflammation take place?
Microcirculation
What is the microcirculation?
- Capillary beds, fed by arterioles and drained by venules
- Extracellular space and fluid around it
- Lymphatic channels and drainage
- Starling forces control the fluid flux across the membrane
- Dynamic balance (hydrostatic/colloid osmotic pressures, compartments and physical constants
What is the pathogenesis of acute inflammation? (Steps)
Changes in the arterial radius (FLOW)
Changes in the permeability of the vessel wall (EXUDATION)
Movement of neutrophils from the vessel to the extravascular space
What are the local changes in vessel radius and blood flow?
- Transient arteriolar constriction (few movements, probably protective)
- Local arteriolar dilation (active hyperaemia)
- Relaxation of vessel smooth muscle (autonomic NS/mediator derived)
What is the triple response?
Flush, flare, wheal.
What does an increased arteriolar radius cause?
Increased blood flow to the local tissue- results in the cardinal redness and heat.
What does increased permeability involve?
There is an endothelial leak-fluid and protein is not held in the vessel lumen due to an imbalance of Starling forces. It also involves locally produced chemical mediators.
What are the effects of increasing permeability?
There is a net movement of plasma from the capillaries to the extravascular space. This process is called exudation- the fluid leaked is called the exudate.
What is an exudate rich in?
Immunoglobulin and fibrinogen.
What are the effects of exudation?
Oedema- accumulation of fluid in the extravascular space
Explains swelling as a cardinal sign of inflammation- this can lead to a localised loss of function in the affected area. Oedema.
Where are plasma, WBC and erythrocytes situated within the vessel during normal laminar flow?
Plasma all around, WBC in middle, erythrocytes surrounding them.
Where are plasma, WBC and erythrocytes situated within the vessel during inflammation?
Plasma remains, WBC extend to the surface, erythrocytes (RBC) move into the middle.
What are the phases of neutrophil emigration?
When neutrophils migrate from pre-endothelium in the vessel to the extravascular space.
What are the phases of neutrophil emigration?
- Margination- neutrophils move to the endothelial aspect of the lumen
- Pavementing- neutrophils adhere to the endothelium
- Emigration- neutrophils squeeze between endothelial cells (active process) to the extravascular tissues
What are the outcomes of acute inflammation?
Resolution
Suppuration (pus formation)
Organisation
Chronic inflammation
What is the ideal outcome of acute inflammation?
- Inciting agent is isolated and destroyed (pathogenic destruction)
- Macrophages move in from the blood and phagocytose debris then leave
- Epithelial surfaces regenerate
- Inflammatory exudate filters away
- Vascular changes return to normal
- Inflammation resolves
What are the benefits of acute inflammation?
- Rapid response to a non-specific insult
- Cardinal signs and loss of function provide transient protection of the inflamed area
- Neutrophils destroy organism and denature the antigen for macrophages
- Plasma proteins localise the process
- Can be resolved and restored to normal
What is inflammation characterised by in terms of nomenclature?
-‘itis’ prefix
What is inflammation called in the lungs?
Pneumonia
What is inflammation called in the pleural cavity?
Pleurisy
What do neutrophils do?
Neutrophils are mobile phagocytes- they recognise foreign antigens and move towards them in the chemotaxis process. They then adhere to them. Granules produce oxidants and enzymes which phagocytose and destroy the foreign antigen.