Theme 3: Inflammation, Infection and Immunology: Part 1 Flashcards
What is acute inflammation?
- initial tissue reaction to injury
- response is same no matter what causes injury
- lasts minutes, hours or days
What is the characteristic cell in acute inflammation?
neutrophil polymorph
What are the 5 signs of acute inflammation?
- Redness (rubor) - caused by vasodilation
- Heat (calor) - caused by increased blood flow to vessels or systemic fever due to cytokines
- Swelling (tumor) - results from oedema - accumulation of fluid extra cellular space
- Pain (dolor) - results from distortion of tissues or pus under pressure
- Loss of function (functio laesa)
What are the causes of AI?
- physical agents - burns, radiation
- infections
- hypersensitivity reactions- autoimmune
- chemicals
- tissue necrosis e.g from MI
Where is the inflammation in meningitis?
subarachnoid space in brain
What is acute cholecystitis and what is it often caused by?
inflammation of the gall bladder
often caused by gallstones
What are empyema?
pockets of pus that have collected inside a body cavity - can develop during AI
What is exudate?
extra vascular fluid with high protein concentration, containing cellular debris. Implies inflammation
What is transudate?
low protein, little or no cellular component
What is oedema?
excess fluid in interstitial tissue/serous cavities
can be exudate or transudate
What is pus?
inflammatory exudate rich in neutrophils, dead cell debris and microbes
What are the 3 occurrences in acute inflammation?
- changes in vessel calibre
- increased vascular permeability and fluid exudate formation (fluid enters tissue)
- cellular exudate formation (cells enter tissue)
Explain the changes in vessel calibre during AI?
- vasodilation
- increased blood flow
- heat and redness
- mediated by histamine and NO on vascular smooth muscle
What is exudation?
- increased permeability of vessels
- protein rich fluid escapes into tissue
- hydrostatic pressure increases and plasma proteins escape into extravascular space increasing the osmotic pressure
- fluid leaves vessel : exudation
What are the 7 effects of fluid exudate?
- dilution of toxins
- entry of antibodies
- transport of drugs
- fibrin formation
- delivery of nutrients and oxygen
- stimulation of immune response
- responsible for swelling
Why does stasis occur in AI?
- loss of fluid into tissues and increased calibre of vessels
- slower blood flow and increased viscosity
How does the formation of the cellular exudate occur?
- Margination of neutrophils
- Pavementing of neutrophils
- Pass between endothelial cells
- Pass through basal lamina and migrate into adventitia
- Gap seals itself behind
(neutrophils line up along the vascular endothelium, stick to the endothelium and migrate through walls into tissues)
What is margination?
usually neutrophil polymorphs travel down the centre but as blood thickens they move to the side and exit the vessel
What is chemotaxis?
movement of a motile cell or organism, in a direction corresponding to a gradient of increasing or decreasing concentration of a particular substance
give 5 features of neutrophils
- produced in bone marrow
- commonest white cell in blood
- increased in acute inflammation
- motile, amoeboid, can move into tissues
- short lifespan
- directional chemotaxis
Which chemical mediators of AI are cell derived?
- histamine - released by mast cells which increases vascular permeability and dilatation
- prostaglandins - come from arachidonic acid with vasodilator properties
- lysosomal components
- leukotrines - come from arachidonic acid with vasodilator properties
- cytokines
What are the systemic effects of inflammation?
- pyrexia (fever)
- lymph node enlargement
- nausea, malaise, anorexia
- leukocytosis
What is fibrinous inflammation?
- increased vascular permeability can result in large molecules such as fibrinogen entering tissues and forming fibrin
- causes inflammation in linings of body cavities
- can be removed by fibrinolysis and removal of debris by macrophages
- if not can lead to scarring (organisation)
What is the ideal outcome of AI?
Resolution - tissue restores to normal. This only occurs when there is minimal cell death and depends on the regenerative capacity of the organ or tissue