acute inflammation Flashcards
what is the definition of acute inflammation?
fundamental response maintaining integrity of organism ( dynamic homeostatic mechanism)
series of protective changes occurring in living tissue as a response to injury
what are the cardinal signs of inflammation?
rubor - redness calor - heat tumor - swelling dolor - pain loss of function
what is the aetiology of acute inflammation?
pathogenic organisms
mechanical trauma or injury to tissue (occurs in all injuries even those that are sterile)
Chemical - upset stable environment (acid or akali)
physical - extreme conditions such as heat, cold or ionising radiation
dead tissue - cell necrosis
HYPERSENSITIVITY
what is the process of acute inflammation?
series of events
localised to affected tissue
takes place in the microcirculation
result in the cardinal signs of inflammation
what is the microcirculation?
capillary beds, fed by arterioles and drained by venules
STARLING FORCES CONTROL FLOW ACROSS MEMBRANE
there is a dynamic balance, which is maintained by HYDROSTATIC AND COLLOID OSMOTIC PRESSURE and COMPARTMENTS AND PHYSICAL CONSTANTS
lymphatic channels and drainage
extracellular “space” and the fluid and molecules within it
what are the steps - pathogenesis - in acute inflammation?
changes in vessel radius - flow
change in the permeability of the vessel wall - exudation
movement of neutrophils from the vessel to the extravascular space
what changes take place locally in vessel radius and blood flow during acute inflammation?
transient arteriolar constriction
local arteriolar dilation - hyperaemia
relaxation of vessel smooth muscle
known as the triple response - flush,flare,wheal
what is the effect of increased arteriolar radius?
increased local tissue blood flow which results in observed redness and heat - active hyperaemia
poiseuille’s law
what is increased permeability and what happens when it increases.
localised vascular response
microvascular bed
endothelial leak - fluid and protein not held in the vessel lumen
locally produced chemical mediators
what are the effects of increased permeability?
net movement of plasma from capillaries to extravascular space
process is called exudate
exudate is the name given to the fluid which leaks
exudate is rich in protein
fluid loss - which leads to increased viscosity and decreased flow (stasis)
what are the effects of exudation?
oedema formed
oedema is an accumulation of fluid in the extravascular space
causes swelling in acute inflammation
swelling causes pain - reduce function
what is the pattern of normal laminar flow?
neutrophils on the inside, eryhtrocytes on the outside, plasma contained within the cell
what happens to laminar flow in acute inflammation?
red cells aggregate in the centre of the lumen
neutrophils found near the endothelium
neutrophil polymorphonuclear leukocyte (NPL) is most important cell
what are the phases of neutrophil emigration?
margination - neutrophils move to endothelial aspect of lumen
pavementing - neutrophils adhere to endothelium
emigration - neutrophils squeeze between endothelial cells to extravascular tissues
how would acute inflammation be resolved?
inciting agent is isolated and destroyed macrophages move in from blood and phagocytose the 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 non specific insult
cardinal signs and loss of function provide transient protection of inflamed area
neutrophils destroy organisms and denature antigen for macrophages
plasma proteins keep the process localised
resolution and eventual return to normal function
what are the possible outcomes of acute inflammation?
resolution
suppuration
organisation
chronic inflammation
what do neutrophils do?
recognise foreign antigen move to towards it - chemotaxis adhere to organism they release granule content which contain oxidants and enzyme phagocytose and destroy foreign antigen
what are some consequences of neutrophil action?
die after granule contents released
produce a mixture of fluid, bits of cells, organisms, endogenous proteins - pus
pus may extend into other tissues, progressing the inflammation
what are the two plasma proteins involved in inflammation?
fibrinogen and immunoglobulins
what are the roles of plasma proteins in inflammation?
fibrinogen is a coagulation factor which forms fibrin and clots the exudate - localises inflammatory process
immunogloblulins are part of the humoural immune response
what are the mediators of acute inflammation?
molecules on endothelial cell surface membrane
molecules released from cells
molecules in the plasma
what are some collective effects of mediators?
vasodilatation increased permeability neutrophil adhesion chemotaxis itch and pain
why are cell surface mediators sticky?
adhesion molecules appear on endothelial cells e.g. to help neutrophils stick
P-selectin interacts with neutrophil surface
what molecules are released from cells during acute inflammation?
histamine - released is a result of local injury (IgE mediated). also causes vasodilatation and increased permeabilty
serotonin - released when platelets degranulate in coagulation, causes vasoconstriction
prostaglandins- promotes histamine effects and inhibits inflammatory cells
leukotrienes - neutrophils, vasoactive
omega-3-polyunsaturated fatty acids
platelet activating factor
cytokine and chemokines
nitroc oxide
oxygen free radicals
what four enzyme cascades interact in acute inflammation?
blood coagulation pathways
fibrinolysis
kinin system
complement cascade
what are the immediate systemic effects of inflammation?
pyrexia
feel unwell
neutrophilia - raised white cell count
what are some longer term systemic effects of inflammation?
lymphadenopathy
weight loss
anaemia
what is suppuration?
formation of pus which is then surrounded by a pyogenic membrane
what is an abscess?
collection of pus under pressure
single locule or multiloculated
points and discharges
collapses - healing and repair
what surrounds the abscess cavity?
an ingrowth of granulation tissue
what is a multiloculated abscess?
when pus bursts through the pyogenic membrane surrounding the original cavity to form more cavities
what is empyema?
when pus is in a hollow viscus, such as the pleural cavity
what is pyaemia?
pus discharge to the bloodstream
what is organisition?
an outcome of acute inflammation that is characteristic of granulation tissue, promotes healing and repair and leads to fibrosis and the formation of a scar
what is granulation tissue?
formation of new capillaries - angiogenesis
composed of fibroblasts, collagen and macrophages
what are some consequences of dissemination of acute inflammation?
spread to bloodstream -“septic”
bacteraemia - bacteria in blood
septicaemia - growth of bacteria in blood
toxaemia - toxic products in blood
what are the effects of systemic infection?
shock - inability to perfuse tissues
what are the clinical signs of early septic shock?
tachycardia hypotension peripheral vasodilation pyrexia often sometimes haemorrhagic skin rash
what is the pathogenesis of septic shock?
systemic release of chemical mediators from cells into plasma
decreased Systemic vascular resistance causes tachycardia because the heart rate is increased in order to maintain cardiac output
bacterial endotoxin is released
activation of coagulation - rash
what are the outcomes of septic shock?
rapidly fatal
tissue hypoxia = cell death
haemorrhage
summarise the outcomes of acute imflammation
resolution suppuration organisation dissemination chronic inflammation
