Inflammation
Content
• Inflammation
• Types of inflammation
• Changes involved in acute
inflammation
Objectives
At the end of this PDF, student will be able to
• Define “inflammation”
• Classify inflammation
• Describe the etiology of inflammation
• Identify the signs of inflammation
• Describe the changes involved in acute
inflammation
Inflammation
“Local response of living mammalian tissues to
injury due to any agent “
•
Body
defence reaction to eliminate or limit the spread of injurious agent, followed
by removal of the necrosed cells and tissues
•
Protective response
Etiology of Inflammation
•
Infective agents – bacteria, viruses and their
toxins, fungi, parasites
•
Immunological agents – cell-mediated and antigen antibody reactions
•
Physical agents – heat, cold, radiation, mechanical
trauma
•
Chemical agents – organic and inorganic poisons
Signs of inflammation
4 cardinal signs of inflammation
•
Rubor
(redness)
•
Tumor
(swelling)
•
Calor
(heat) and
•
Dolor
(pain)
Fifth sign – functio laesa (loss of
function) – Virchow
Types of inflammation
Depending upon the defense
capacity of host and duration of response
•
Acute Inflammation
•
Chronic inflammation
Acute Inflammation
•
Short duration
•
Represents early body reaction
•
Followed by repair
Main features
•
Accumulation of fluid & plasma at the
affected site
•
Intravascular activation of platelets
•
Polymorpho nuclear neutrophills (PMN) –
inflammatory cells
Chronic Inflammation
•
Longer duration
•
If causative agent of acute inflammation
persists for long periods
•
Recurrent attack of acute inflammation
Main features:
•
Presence of lymphocytes, plasma cells &
Macrophages as inflammatory cells
Changes in Acute
inflammation
Two main events involved
1. Vascular events
•
Alteration of microvasculature (arteries,
capillaries & venules)
2. Cellular events
•
Exudation of leucocytes
•
Phagocytosis
Vascular events
•
Alteration
in the microvasculature – tissue injury
Haemodynamic Changes
Earliest features – vascular flow change, calibre of small blood vessels
1.
Irrespective of the type of injury –
transient vasoconstriction of arterioles
•
Mild
form – blood flow – 3-5 seconds
•
More
severe injury the vasoconstriction – 5
minutes
Vascular changes
2.
Persistent progressive vasodilatation
•
Mainly
arterioles
•
lesser
extent – venules and capillaries
•
Increased
blood volume – redness and warmth
3.
Progressive
vasodilatation
•
Elevate
the local hydrostatic pressure – transudation of fluid into the extracellular
space – swelling
4. Stasis of microcirculation
•
Increased
concentration of red cells – blood viscosity
5. Leucocytic margination
•
Leucocytes
stick to the vascular endothelium
•
Move
and migrate through the gaps between the endothelial cells into the
extravascular space
•
Emigration
Triple response
Flush
–
Appearance
of red line
–
Local
vasodilatation of capillaries and venules
Flare
–
Bright
reddish appearance or flush surrounding the red line
–
Vasodilatation
of the adjacent arterioles
Wheal
–
Swelling
or oedema of the surrounding
–
Transudation
of fluid into the extravascular space