5 Acute inflammation

Question 1

What is an acute inflammatory response?

Answer 1

It is the most common response of the body tissues to an area of nearby damage

Question 2

What are the 4 cardinal signs of inflammation?

Answer 2

• Calor (Heat)
• Dolor (Pain)
• Rubor (Redness)
• Tumor (Mass)

Question 3

What stimulates the acute inflammatory response?

Answer 3

• Microorganisms (bacteria)
• Trauma (surgical incision)
• Ischaemic necrosis (infarction)
• Radiation damage (sunburn)
• Chemical damage (acids, alkali)

Question 4

What is the purpose of acute inflammatory response?

Answer 4

• To destroy or neutralise the damaging agent
• To liquefy and remove dead tissue
• To prepare the damaged area for healing

Question 5

How does acute inflammatory response occur?

Answer 5

• By the production of an acute inflammatory exudate derived from blood components from capillaries adjacent to damaged mass
• Acute inflammatory exudate compromises:
  > Fluid
  > Fibrin
  > Neutrophils, but also a few macrophages and lymphocytes

Question 6

How does exudate work?

Answer 6

• Fluid dilutes any toxins
• Fluid carries nutrients, mediators, and antibodies
• FIbrin - function is speculative
• NEUTROPHILS

Question 7

Describe the formation of exudate (steps)

Answer 7

• Blood vessels near damaged tissues become dilated
• Blood flow becomes turbulent
• Endothelial cells swell + retract; vessels leak
• Neutrophils marginate and emigrate

Question 8

Describe the events in the first step of exudate formation (blood vessel dilation + loss of axial flow pattern of blood)

Answer 8

• Blood vessels near to damaged tissue become dilated
• Blood flow initially increases (Rubor is a result of this, and calor), then slows down (due to changes in osmotic pressure - blood spends longer in this area)
• Axial flow pattern of blood is lost (turbulent blood flow - cells in the middle of bloodstream are being - on outside of the wall as well)

Question 9

Why does this stage of exudate formation occur? (blood vessel dilation

Answer 9

• Release of inflammatory mediators from damaged tissue
• Area of damaged tissue > mediators released into surrounding tissue - act on blood vessel
• Vessels dilate (histamine affects)

Question 10

Describe the next stage of exudate formation

endothelial cells swell + retract; vessels leak

Answer 10

• Inflammatory mediators affect endothelial cells - they swell
• They now separate, junctions are less robust - increased permeability
• Blood vessels become leaky
• Fluid (exudate) can now exit from the vessel into surrounding tissue
  > smaller molecules first (water, salt)
  > larger molecules follow with more fenestrations (proteins; fibrinogen becomes cross-linked - becomes degraded by enzymes - products of this stimulate other products to move out of vessel too [chemotaxic effect]
• This results in swelling [tumor]

Question 11

Describe the next stage of exudate formation

neutrophils marginate and emigrate

Answer 11

• Exiting of neutrophils from blood vessels into the area of tissue damage
• Turbulence in blood flow -allows neutrophils to move from the middle of vessels to edges, and allows it to leave vessels
• Inflammatory mediators > make endothelial cells express different receptors on the surface - once they meet neutrophils - they make the neutrophils adhere to them on the side of the blood vessels (margination)
• Once they marginate, inflammatory mediators send signals causing chemotaxis - polymorphs (neutrophils) are now induced by chemical signals to exit blood vessels and enter the area of tissue damage
• In this time, fibrin is polymerised (from fibrinogen) and released

Question 12

List the clinical types of exudate

Answer 12

• Serous: excess fluid accumulation - in the pericardial sac
• Purulent: (lots of neutrophils) can be found in meninges
• Fibrinous (lots of fibrin)
• Fibrino-purulent (lots of fibrin and cross-linked fibrin - and pus

Question 13

Describe the mediators of inflammation

Answer 13

They can cause vascular and cellular changes
- Mediated by a series of mediators of acute inflammation

e.g. 
o	Complement system
o	Coagulation system
o	Fibrinolytic system
o	Kinin system
o	Platelet-activating factor
o	Histamine
o	Serotonin
o	Nitric oxide
o	Endotoxin

Question 14

What are selectins and integrins?

Answer 14

• Selectins and integrins are adhesive molecules on the surface of endothelial cells
• These allow polymorphs to enter cells to enter cells
• These also have chemotactic effects - attracting cells to leave vessels