2. Acute inflammation - consequences (+ types of exudate)

Question 1

Describe 4 possible local complications of acute inflammation.

Answer 1

1. Damage to normal tissue - secondary to neutrophil-produced ROS released in phagocytosis
2. Obstruction of tubes (e.g. bile duct, intestine), compression of vital structures (e.g. cardiac tamponade) or serositis - secondary to swelling from inflammatory exudate
3. Loss of fluid from a surface wound, e.g. burns (in tissue spaces, as fluid accumulates to tissue pressure increases until it reaches a level that prevents further exudation)
4. Pain and loss of function

Question 2

Name 3 systemic effects of AI.

Answer 2

1. fever
2. leucocytosis (increased WBC count)
3. acute phase response

Question 3

What causes fever in AI?

Answer 3

1. ‘Exogenous pyrogens’ (esp. bacterial endotoxin) stimulate macrophages to produce ‘endogenous pyrogens’: cytokines such as TNFa and IL-1.
2. Cytokines cause increase in synthesis of prostaglandin E2 by anterior hypothalamus.
3. Prostaglandin E2 increases temp.

Question 4

Why can fever be a useful AI response?

Answer 4

i) some bacteria can’t survive at high temperatures (40-41 degrees)
ii) inflammation is more effective at higher temperatures

Question 5

What causes leucocytosis in AI?

Answer 5

Macrophages and endothelial cells in injured tissues produce colony-stimulating factors (CSF)… stimulate bone marrow to produce more neutrophils.

Question 6

What is the acute phase response?

Answer 6

Cytokine (IL-1, IL-6 and TNFa)-mediated change in the levels of some plasma proteins (within hrs of injury) as a result of liver changing its pattern of protein synthesis (decreased albumin, increased e.g CRP)

Causes decreased appetite, raised pulse rate and altered sleep patterns.

Question 7

The acute phase response increases the synthesis of which proteins?

Answer 7

1. C-reaction protein (CRP) - opsonisation
2. fibrinogen - blood coagulation
3. C3 - complement
4. a1-antitrypsin - protease inhibitor
5. ceruloplasmin - free radical scavenger
6. haptoglobin - binds haemoglobin

Question 8

What are the effects of bacterial products/inflammatory mediators spreading in the blood stream?

Answer 8

Inflammation/acute phase response occurs throughout body… shock = dramatic drop in BP due to widespread vasodilation and increase in vascular permeability with resultant fluid exudation.

Question 9

What are the 4 possible results of acute inflammation?

Answer 9

1- complete resolution
2- continued acute inflammation with chronic inflammation - abscess
3- chronic inflammation and fibrous repair, probably with tissue regeneration
4- death

Question 10

Describe the process of AI resolution.

Answer 10

1) Absence of mediators… normal vascular permeability returns… cessation of neutrophil emigration.
2) Exudate is reabsorbed into venules or is drained away in lymphatics.
3) Fibrin is degraded by plasmin and other proteases.
4) Neutrophils apoptose and are phagocytosed along with necrotic debris by macorphages.
5) If damaged parenchymal cells can regenerate, tissue returns to normal. If regeneration cannot occur or damage has been extensive, a fibrous scar forms.

Question 11

How are chemical mediators removed upon resolution?

Answer 11

1- all mediators have short 1/2 lives

Mediators may be:
2- unstable, e.g. some arachidonic acid derivates (prostaglandins)
3- diluted in exudate, e.g. fibrin degradation products
4- inactivated by degradation, e.g. heparinase
5- bound by inhibitors, e.g. various anti-proteases

+ specific inhibitors of acute inflammatory changes

Question 12

Name 4 different types of exudate.

Answer 12

1. pus
2. haemorrhagic exudate
3. serous exudate
4. fibrinous exudate

Question 13

What is pus and what does it indicate?

Answer 13

• Creamy/white exudate (as rich in neutrophils) from abscess.
• Typical of infections by chemotatic bacteria.

Question 14

What is haemorrhagic exudate and what does it indicate?

Answer 14

• Appears bloody as many RBCs.
• Indicates significant vascular damage as well as inflammation - seen in destructive infections or when exudate is a result of infiltration by a malignant tumour.

Question 15

What is serous exudate and what does it indicate?

Answer 15

• Clear as contain plasma proteins but few leucocytes - suggests there is no MO infection.
• Typically seen in blisters, e.g. after mild burn.

Question 16

What is fibrinous exudate and what does it indicate?

Answer 16

• Significant deposition of fibrin (i.e. blood clot without RBCs).
• If occurs in pericardial or pleural spaces, prevents serosal surfaces from sliding smoothly over each other. Resulting friction can be heard as rubbing sound.