Inflammation - B. Pharma 2nd Semester Pathophysiology notes pdf

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

Pathogenesis of altered vascular permeability

Normal circumstances - fluid balance - two opposing sets of forces that causes:

Outward movement of fluid from microcirculation

–      intravascular hydrostatic pressure

–      colloid osmotic pressure of interstitial fluid

Inward movement of interstitial fluid into circulation

–      intravascular colloid osmotic pressure

–       hydrostatic pressure of interstitial fluid

Contraction of endothelial cells

•       Increased leakiness - venules exclusively

•       Endothelial cells - temporary gaps – contraction - vascular leakiness - release of histamine, bradykinin and others

•       Response - immediately after injury – reversible - short duration (15-30 minutes)

•       Example: immediate transient leakage is mild thermal injury of skin of forearm

Retraction of endothelial cells

•       structural re-organisation of the cytoskeleton of endothelial cells - reversible retraction – intercellular junctions – venules - cytokines such as interleukin-1 (IL-1) and tumour necrosis factor (TNF)-α - response takes 4-6 hours after injury - lasts for 2-4 hours or more

•       The example invitro experimental work only

Direct injury to endothelial cells

•       Cell necrosis, physical gaps at the sites of detached endothelial cell - thrombosis at site initiated

•       Affects – microvasculature -  immediately after injury  last for several hours or days or  delay of 2-12 hours and last for hours or days

Summary

•       Inflammation is the local response of living mammalian tissues to injury due to any agent

•       The four cardinal signs of inflammation are redness, swelling, heat and pain

•       Inflammation is of 2 type acute and chronic inflammation

•       Acute inflammation is of Shorter duration , represents early body reaction, followed by repair

•       Chronic inflammation is of longer duration and occurs when the agents remains for longer time

•       Acute inflammation is characterized by cellular events and vascular events