Inflam Flashcards
Acute inflammation definition
- Fundamental response maintaining integrity of organism
- Series of protective changes occurring in living tissue as a response to injury
Causes of acute inflammation
- Micro-organisms, pathogenic organisms
- Mechanical, trauma
- Chemical, upset to stable environment. Acid or alkali, bile or urine in wrong place
- Physical, sunburn, frostbite, ionising radiation
- Hypersensitivity, several classes of reaction
Benefits of acute inflammation
- Rapid response to non-specific insult
- Cardinal signs and loss of function, act as transient protection of inflamed area
- Neutrophils destroy organisms and denature antigen for macrophages
- Plasma proteins localise process
- Resolution and return to normal
Sequence of microvascular change
- Flush - transient arteriolar constriction
- Flare - local arteriolar dilatation
- Wheal - relaxation of vessel smooth muscle
Mechanisms of microvascular change
- Change in the vessel radius which results in increased flow
- Permeability of the vessel is increased to allow for exudation
- Neutrophils move from the vessel to the extracellular space
Sequence of events in exudate formation
- Increased permeability: plasma moves from capillaries to extravascular space
- Exudation
- A fluid rich in protein, plasma with immunoglobulin and fibrinogen is leaked
- Oedema formed, accumulation of fluid in extravascular space
- Swelling of tissue in inflammation, causes pain and reduction in function
How neutrophils get through the capillary beds
- Blood is non-Newtonian fluid
- In laminar flow, bigger molecules are closer to the centre
- In turbulent flow, red cells aggregate in the centre of the lumen and the neutrophils are found near the endothelium
- Neutrophils then adhere to the endothelium and squeeze out of the endothelial cells to extravascular tissues
Local effects of acute inflammation
- Rubor: redness
- Calor: heat
- Tumor: swelling
- Dolor: pain
- Loss of function, you protect it
Immediate systematic effects
- Pyrexia: raised temperature. Endogenous pyrogens from white cells act centrally
- Feeling unwell: Malaise, anorexia, nausea. Abdominal pain and vomiting in children
- Neutrophilia: raised white cell count. Bone marrow releases/produces
Long term systematic effects
- Lymphadenopathy: regional lymph node enlargement
- Weight loss: as inflammation is a catabolic process
- Anaemia
Suppuration features
- Pus formation
- Pyogenic membrane surrounds pus
- Abscess
- Empyema - in a hollow viscus
- Pyaemia
Pus formation
- Dead tissue, organisms, exudate, neutrophils, fibril, red cells, debris
Pyogenic membrane
- Capillary sprouts, neutrophils, fibroblasts
- Walls off the pus
Abscess
- Collection of pus under pressure
- Single locule, multiloculated: when the pus bursts through the pyogenic membrane and forms new cavities
- ‘Points’ and discharges
- Collapses - healing and repair
Empyema
- In a hollow viscus (internal organ)
- Gall bladder
- Pleaural cavity
Pyaemia
Discharge into bloodstream
Role of neutrophil
- Mobile phagocytes
- Chemical blast
- Release of granule contents
- Phagocytose and destroy foreign antigen
Mobile phagocytes
- Recognise foreign antigen
- Move towards it - chemotaxis (based on concentration gradient)
- Adhere to organism
Chemical blast
- Granules possess oxidants and enzymes
- Oxidants liberate oxygen and water and they pick up various molecules with charge
- Enzymes catalyse a reaction that picks up specific chemicals, it’s a more specific response
Consequences of neutrophil action
- Neutrophils die when granule contents are released
- A ‘soup’ of fluid with bits of cell, organisms and endogenous proteins called pus is released
Fibrinogen
- Plasma proteins in inflammation
- Coagulation factor, forms fibrin and clots exudate, localises inflammatory process
- Stack of fibrinogen, some cleave off and active sizes are available, forms fibrin, then a clot
- Increases permeability and acute inflammation, fibrinogen can go to affected site
Immunoglobulins in plasma specific for antigen
- Plasma proteins in inflammation
- Humoral immune response
Types of mediators of acute inflammation
- Molecules on endothelial cell surface membrane
- Molecules released from cells
- In the plasma, fibrinogen and kinins
Molecules on endothelial cell surface membrane
- ICAM-1 on endothelial
- P-selectin on neutrophil surface
Histamines
- Released from cells
- Makes stuff leakier
- Preformed in mast cells where it’s needed - blood vessels, platelets and basophils
- Released as a result of local injury
- Vasodilatation and permeability
- Acts via H1 receptors on endothelial cells
Serotonin
- Released from cells
- When you want it to be less leaky
- Preformed in platelets
- Released when platelets degranulate in coagulation
- Vasoconstriction
Histamines vs. serotonin
- You have a tendency towards histamine or serotonin depending on the situation
Prostaglandins
- Released from cells
- Many cells (endothelium and leukocytes)
- Many promote histamine effects and inhibit inflammatory cells
- Some promote platelet aggregation and vasconstriction
Leukotrienes
- Released from cells
- Neutrophils especially
- Vasoactive - dynamic effect on vessels to increase permeability and constrict smooth muscle
Omega-3 polyunsaturated fatty acids
- Released from cells
- Decrease synthesis of arachidonic acid derived inflammatory mediators
Platelet-activating factor (PAF)
- Released from cells
- Cell membrane of activated inflammatory cells
- Reduces permeability by enhancing platelet degranulation at site of injury
Cytokines and chemokines
- Released from cells
- Small molecules produced by macrophages, lymphocytes, endothelium in response to inflammatory stimuli
- Attract inflammatory cells
Nitric oxide
- Released from cells
- Various cells
- Smooth muscle relaxation, anti-platelet, regulate leukocyte recruitment to inflammatory focus
Oxygen free radicals
- Released by neutrophils on phagocytosis
- Amplify other mediator effects
Mediators of inflammation in plasma
- Blood coagulation pathways, clots fibrinogen in exudate
- Fibinrolysis: breaks down fibrin, helps maintain blood supply, vasoactive
- Kinin system: bradykinin pain, built upon the stimulation of the PNS, tells brain there’s pain
- Complement cascade: ties inflammation with immune system, active components stimulate increased permeability, chemotaxis, phagocytosis, cell breakdown
Effects of mediators
- Vasodilatation
- Increased permeability
- Neutrophil adhesion
- Chemotaxis
- Itch and pain
Neutrophil adhesion
- Neutrophils and endothelial cells both have mediators on the outside that are compatible which creates the stickiness
Dissemination
- Spread to bloodstream: bacteraemia, septicaemia, toxaemia
Steps in septic shock
- Peripheral vasodilatation: mediators cause vasodilation, loss of systemic vascular resistance (build in pressure)
- Tachycardia: catecholamine released, adrenaline and noradrenaline. Tachycardia tries to maintain cardiac output
- Hypotension
- Pyrexia: bacterial endotoxin released, acts on hypothalamus
- Haemorrhagic skin rash: activation of coagulation
Septic shock can lead to
- Tissue hypoxia
- Loss of cell tissue and organ function
This is because the heart rate is insufficient to maintain cardiac output and there can be reduced perfusion of tissues
4 outcomes of inflammation
- Resolution
- Suppuration - pus
- Organisation - healing
- Dissemination - sepsis
- Chronic inflamation