Acute Inflammation Flashcards
What is acute inflammation?
a dynamic homeostatic mechanism by which a series of protective changes occur in living tissue as a response to injury
What are the 5 Cardinal Signs of acute inflammation?
dolor-pain calor-heat rubor-redness tumour-swelling loss of function
What are 6 examples of causes of acute inflammation?
- microorganisms
- mechanical trauma - injury to tissue
- chemical- bile and urine - irritation when in wrong place
- physical - extreme conditions - sunburn, frostbite
- dead tissue - cel necrosis irritates adjacent tissue
- hypersensitivity
Give a basic description of what acute inflammation is.
- series of microscopic events
- localised to affected tissue
- take place in microcirculation
- results in cardinal signs
What is the microcirculation?
capillary beds, extracellular space and fluid and molecules in it, lymphatic channels and drainage
starling forces control flow (fluid flux) across membrane
What are the 3 main steps in acute inflammation?
- changes in vessel radius - flow
- change in permeability of vessel wall - called exudation
- movement of neutrophils from vessel to to extravascular space
Describe the process by which there is a change in the flow in the blood vessel.
- transient arteriolar constriction
- local arteriolar dilation - active hyperaemia
- relaxation of vessel smooth muscle
Why does an increase in radius result in an increase in flow?
- poiseuille’s law - flow is proportional to the radius to the power of 4
- an increase in arteriolar radius causes an increase in local tissue blood flow
- results in observed redness and heat
Describe the basics behind the increase in permeability stage of acute inflammation.
- localised vascular response that will occur in the microvascular bed
- a result of locally produced chemical mediators
- results in endothelial leak - fluid and protein not held in vessel lumen
What is exudate?
fluid rich in protein - plasma
includes immunoglobulin and fibrinogen
What are the effects of exudation?
oedema formed (accumulation of fluid in extravascular space)
this explains the swelling of tissue
causes pain
What is another effect of increased permeability?
fluid loss- increased viscosity
rate of flow slows -stasis
Describe basics of flow in acute inflammation. (In reference to blood cells)
Red cells aggregate in centre of lumen
neutrophil polymorphonuclear leukocytes found near endothelium
What are the 3 phases of emigration of neutrophils?
- margination -move to endothelium of lumen
- pavementing - neutrophils adhere to endothelium
- emigration - neutrophils squeeze between endothelial cells
What occurs in the resolution of acute inflammation?
- inflammation resolves
- cause of inflammation eradicated
- epithelial surfaces regenerate
- inflammatory exudates filter away
What do neutrophils do?
- recognise antigen and move towards it via chemotaxis and adhere to organism
- granules possess oxidants and enzymes
- release granule contents
- phagocytose and destroy foreign antigens
What happens after the neutrophils have finished doing their job?
- the neutrophils die after granule contents released
- pus is produced (it is a soup of fluids, organisms and endogenous proteins)
- pus might extend into other tissues, progressing the inflammation
What is the role of plasma proteins in acute inflammation?
- immunoglobulins - specific for antigen - humeral response
- fibrinogen - coagulation factor - forms fibrin and clots exudate - localises inflammatory process
Name 3 general mediators of acute inflammation.
- molecules on endothelial cell surface membrane
- molecules released from cells
- molecules in plasma
Cell surface mediators - functions
to be sticky
ICAM1 helps neutrophils stick
P. Selectin interacts with neutrophil surface
Molecules released from cells
can inhibit or promote acute inflammation
Give an example of a chemical that will inhibit the process of acute inflammation
platelet activation factor on cell membranes of activated inflammatory cells- reduces permeability by enhancing platelet degranulation at site of injury
Give an example of a chemical that will promote the process of acute inflammation.
oxygen free radicals which are released by neutrophils during phagocytosis - amplify mediator effects
Plasma mediators work by interaction of 4 enzyme cascades. Name them.
- blood coagulation pathways
- fibrinolysis - helps maintain blood supply
- kinin system - bradykinin - pain
- complement system - ties inflammation with immune system
3 immediate systemic effects of inflammation
pyrexia - raised temperature
feel unwell - malaise, anorexia, nausea
neutrophilia - raised white cell count
Longer term effects of acute inflammation.
- lymphadenopathy - enlargement of the lymph nodes
- weight loss - catabolic process
- anaemia
What is suppuration?
pus formation
What happens with the pus that forms?
a pyogenic membrane forms around it and walls it off
What is a pyogenic membrane?
the debris e.g. the capillaries, neutrophils, granulation tissue
What is an abscess?
pus under pressure
can be a single local or multiloculated
‘points’ and discharges
collapses - healing and repair
Where other than cutaneously can you find pus?
empyema - in a hollow viscus e.g. gall bladder, pleural cavity
pyaemia - discharge to blood stream
What is characteristic of organisation in acute inflammation?
granulation tissue formation
which is part of healing and repair
leads to fibrosis and formation of a scar
What is granulation tissue?
new capillaries - angiogenesis
fibroblasts and collagen
macrophages
What is meant by ‘septic’?
spread to blood
What is meant by bacteraemia?
bacteria in the blood
What is meant by septicaemia?
growth of bacteria in the blood
What is meant by toxaemia?
toxic products in the blood
What is ‘shock’?
inability to perfuse tissues
How does septic shock present itself clinically?
tachycardia- high heart rate hypotension - low blood pressure peripheral vasodilation often pyrexia sometimes hemorrhagic skin rash
