What is acute inflammation?
A stereotyped, immediate response of a living, vascular tissue to injury in order to limit the tissue damage
What are the cardinal signs of inflammation?
- Heat (calor)
- Swelling (tumor)
- Redness (rubor)
- Pain (dolor)
- Loss of function
What are the features of acute inflammation?
- innate
- immediate and early
- stereotyped (always the same regardless of cause)
- short in duration
What are the main causes of acute inflammation?
infections hypersensitivity reactions trauma physical and chemical agents/ damage tissue necrosis
Outline the 2 key stages of acute inflammation
change in blood flow + exudate formation (vascular phase)
infiltration of inflammatory cells/delivery of neutrophils (cellular phase)
Why cant you get inflammation in cartilage or the lens of the eye?
No/ little blood supply
What changes occur to blood flow in acute inflammation and how? (vascular phase)
- after a few seconds the blood vessels vasoconstrict (not sure why)
- then they dilate to increase blood flow to the area (redness and heat)
- they then become more permeable (so fluid escapes and exudate forms)
what 2 chemical mediators cause increased blood flow and dilation, where are they released from?
histamine and prostaglandins (from mast cells, basophils ect)
What 2 chemical mediators causes increased capillary permeability?
histamine and leukotrienes, bradykinin, c3b and c5a
How does the exudate form?
Increased hydrostatic pressure due to vasodilation means more fluid leaves. Increased permeability means proteins from blood can enter the interstitial fluid which increases its oncotic pressure so less fluid moves back into blood at venous end- leading to swelling
(increased hydrostatic + decreased oncotic pressure)
What are the differences between exudate and transudate? (3)
- transudate has low protein concentration, exudate is protein rich
- increased vascular permeability in exudate, unchanged in transudate
- Exudate occurs in inflammation, transudate in HF/hepatic failure/renal failure
What is the result of water and proteins leaving the blood?
stasis (reduced flow through vessel) - blood becomes more viscous
How are blood vessels made more permeable? (3)
1) histamine makes endothelial cells contract to create gaps by cytoskeletal reorganisation
2) direct injuries (burns) - cause damage to vessel wall
3) leukocyte dependant injury (by toxic o2 species and enzymes released by inflammatory cells)
Outline the steps in infiltration of neutrophils into exudate (cellular phase) - 4 steps
- stasis causes RBCS to aggregate in middle and neutrophils on outline (margination)
- Neutrophils roll along endothelium and stick to it intermediately (rolling)
- IL1 and TNF causes increased expression of adhesion molecules which help it adhere to endothelium (adhesion)
- they relax the cell junctions, digest the basement membrane and then move into interstitial space (emigration)
Give examples of chemoattractants - what do they allow for?
C5a, bacterial peptides - allow neutrophils to move through interstitial towards site of injury via increasing concentration of chemokines.
What mediators cause pain?
bradykinin, substance P, prostaglandins
What local complications can be caused by acute inflammation?
- swelling (via compression of tubes) - e.g.: bile duct
- exudate can compress organs - e.g. cardiac tamponade
- loss of fluid (severe burns)
- pain and loss of function
- shock due to wide spread vasodilation
What are the systemic complications of acute inflammation? (4)
- fever due to pyrogens such as prostaglandins
- leukocytosis (increased production of white cells)- TNF, IL-1, macrophage and endothelial cells stimulate leukocyte release from bone marrow
- acute phase response (reduced appetite, increased pulse, sleep pattern changes, tiredness)
- Septic shock, huge release of chemical mediators leading to widespread hypotension, tachycardia and multi-organ failure
What are possible outcomes to inflammation? (3)
1) Complete resolution - exudate drained by lymphatics, mediators short t1/2, neutrophils undergo apoptosis, tissue undergoes regeneration.
2) Repair w/connective tissue (fibrosis) - if theres been substantial tissue destruction.
3) Progression to chronic inflammation - prolonged inflammation with repair
What is lobar pneumonia
- exudate in alveolar sacs due in strep. pneumoniae infections
- characterised by fever, dry cough, dysopnea
only effects a single lobe- bronchopneumonia effects multiple lobes supplied by same bronchus
What is most common cause of appendicitis?
- obstruction/blockage of lumen
- appendix invaded by gut flora/bacteria
- Increased pressure + perforation
What is seen in autopsy of brain with meningitis?
purlent exudate in sulci
Name 2 causative organims of meningitis
neisseria meningitidis,
strep pneumonia
group b streptococcus
Give possible complications of meningitis
seizures walking difficulty, cognitive impairment, inconenance, deafness amputations sepsis abcesses thrombosis
