Inflammation-1 Lecture Notes PDF

INFLAMMATION-1 Dr.Gehan Abdelmenam  Intended Learning Objectives Recall definition, nomenclature, causes and types of inflammation. Describe Pathogenesis of acute Inflammation. Describe mechanism, characters and function of Inflammatory Fluid Exudate.  Inflam...

INFLAMMATION-1 Dr.Gehan Abdelmenam  Intended Learning Objectives Recall definition, nomenclature, causes and types of inflammation. Describe Pathogenesis of acute Inflammation. Describe mechanism, characters and function of Inflammatory Fluid Exudate.  Inflammation Definition: Local tissue, vascular and Lymphatic reactions of living tissue against an irritant. *Inflammation is a protective mechanism with the purpose of: To defend against and eliminate the injurious agent responsible for injury and prevent its spread. Removal of the consequences of injury (necrotic cells). To start repair of injured tissue.  * Nomenclature of inflammation: Inflammation is designated by adding the suffix “itis” to the English, Latin or Greek name of the organ affected : Examples: Appendix appendicitis Fallopian tube salpingitis Ovary oophritis Pericardium pericarditis Liver hepatitis Joints Arthritis Rectum proctitis Testis orchitis Vein phlebitis umbilicus omphalitis * Causes of inflammation: (1) Living Irritants: Bacteria and their toxins, viruses, parasites and fungi. (2) Non Living Irritants: include: (a) Physical irritants: e.g. excess heat, excess cold and radiations. (b) Chemical irritants: e.g. concentrated acids, alkalis, poisons. (c) Mechanical irritants: e.g. trauma, mechanical friction and foreign bodies. (d) Immunological: e.g. allergic inflammation.  TYPES OF INFLAMMATION 1. Acute Inflammation: Characterized by sudden onset and short duration (days to weeks). 2. Chronic inflammation: Characterized by gradual onset and long duration (months to years). Acute Inflammation  * Pathogenesis of acute Inflammation: The acute inflammatory reaction consists of: Local tissue reactions. II. Local vascular reactions.  I. Local tissue reactions: Occurs at the center of the inflamed area with the maximum concentration of the irritant resulting in. Local death of tissue (necrosis). This local damage of cells together with inflammatory stimulus trigger the release and activation of chemical substances called chemical mediators as histamine, serotonin and prostaglandins. These chemical mediators play an important role in promoting the vascular and cellular changes in the inflamed area. II. Local vascular reactions - Occur in this sequence: 1.Transient vasoconstriction of the small arterioles: * Caused by: the direct effect of the irritant on the vascular wall. * Leads to: - Vasoconstriction is a protective mechanism and lasts for seconds to minutes only.  2. Vasodilatation of the arterioles, venules and capillaries: * Caused by: a. Direct action of histamine on the vascular wall. b. Local nerve axon reflex. * Leads to: - increase the blood flow to the inflammed area (hyperaemia). - The inflamed area becomes red and hot. 3. Slowing of the Blood Stream (Stasis): Caused by: a. Increased viscosity of the blood due to formation inflammatory fluid exudates. This is the main cause of stasis. b. Histamine causes swelling of the vascular endothelium which become sticky and offer mechanical resistance to the blood.  4. Formation of the Inflammatory Exudates: - The intravascular contents (plasma and cells) escape into the interstitial tissue spaces forming the inflammatory exudates which consists of: Inflammatory fluid exudate. Inflammatory cellular exudate (leucocytes). 5. Dilatation of lymphatic vessels: - Occurs at the end of inflammation to drains the fluid exudates. Exudate : microscopy Neutrophils Exudate rich in fibrin  A. The Inflammatory Fluid Exudate * Mechanism of formation: 1. Increased capillary permeability caused mainly by histamine. 2. Increased capillary hydrostatic pressure due to dilatation of the arterioles and increased blood flow. This leads to a pushing force from the capillaries. 3. Increased osmotic pressure of the interstitial tissue fluid as the large protein molecules split into smaller ones in the process of tissue necrosis. This acts as a suction force from the capillaries. * Characters of inflammatory fluid exudate: - High protein content, 4-8 gm% (the normal interstitial tissue fluid contains 1 gm% protein). - High fibrinogen content responsible for turbidity & clotting on standing). - High specific gravity (above 1018). - High cellular content (polymorphs & macrophages) * Functions: 1. It dilutes toxins, chemicals and poisons, so minimizes their effects. 2. Brings antibodies from the blood to the site of inflammation. 3. Supplies nutrition for the cells and carries away waste products. 4. Fibrinogen forms a fibrin network, which acts as a mechanical barrier to the spread of infection and as a bridge for leucocytes to reach the irritant.  REFERENCES Robbins and Cotran Pathologic Basis of Disease, 9th edition, 2014 ( Kumar, Abbas, Aster) Robbins Basic Pathology 10th edition, 2017 ( Kumar, Abbas, Aster)