Inflammation

Definition: Inflammation of the dynamic process by which living tissues react to injury. (Ref- Reid & Roberts/ 6^th /32)

Definition (Acute inflammation): Acute inflammation is the inflammation which is rapid in onset (Seconds or minutes) and is relatively short in duration (lasting for minutes, several hours or a few days) which is characterized by the exudation of fluid and plasma protein (edema) and the emigration of leukocytes, predominantly neutrophils.

Fates/Outcomes of acute inflammation:

1.     Complete resolution: Resolution means the complete return to normal of a tissue following acute inflammation. Usually it occurs-

a)     When the injury is limited or short lived.

b)    When there has been little tissue destruction and the damaged parenchymal cells can regenerate.

2.     Abscess formation: If causative is pyogenic organism.

3.     Healing by connective tissue replacement (fibrosis): This occurs when the injured tissue cannot regenerate.

4.     Progression to chronic inflammation: If causative agent persist or there is interference of repair.

Definition (Chronic inflammation): It is define as inflammation of prolonged duration (weeks or months) in which active inflammation, tissue destruction and attempts at repair are proceeding simultaneously.

Cardinal signs of acute inflammation:

1.     Readness

2.     Swelling

3.     Heat

4.     Pain

5.     Loss of function

Differences between acute & chronic inflammation:

Traits	Acute inflammation	Chronic inflammation
1.     Common cause	Pyogenic bacteria	Tubercle bacilli, lepra bacilli etc
2.     Duration	Hours to days	Weeks to months
3.     Character	Exudative	Proliferate, Granuloma may form
4.     Vascular phenomenon	Prominent	Not prominent
5.     Fluid exudate	Marked	Usually scanty
6.     Cellular exudate	Early neutrophil then macrophages in most cases	Mononuclear cells in most cases
7.     Repair process	Follows	Starts concurrently
8.     Example	Acutetoasilitis, acute appendicitis	Tuberculosis, Leprosy, Syphilis etc

Name the chemical mediators of inflammation:

1.     Cellular	a)     Preformed	Ø Histamin Ø Serotonin Ø Lysosomal enzymes
	b)    Newly synthesized	Ø Prostaglandins Ø Leukotrienes Ø Platelate activating factore (PAF) Ø Activated oxygen species Ø Nitric oxide Ø Cytokines
2.     Plasma	a)     Factor XII (Hageman factor) activation	Ø Kinin system (Bradykinin) Ø Coagulation/fibrinolysis system
	b)    Complement activation	Ø C3a Ø C5a Ø C3b Ø C5b-9 (membrane attack complex)

Functions of chemical mediators of inflammation:

Function	Chemical mediators
1.     Vasodilatation	Prostaglandins, Nitric oxide, histamine
2.     Increase vascular permeability	Vasoactive amines C3a & C5a (through liberating amines) Bradykinin Leukotrienes C4,D4,E4 PAF (Platelet activating factor) Substance P
3.     Chemotaxix, leukocyte recruitment and activation	C5a Leukotriene B4 Chemokines Bacterial products
4.     Fever	IL-1, TNF Prostaglandins
5.     Pain	Prostaglandins, Bradykinin
6.     Tissue damage	Neutrophil & macrophage lysosmal enzymes Oxygen metabolies Nitric oxide