INFLAMMATION Definition ; It is local changes occur in the living tissue when exposed to injury , provided that the injury is not severe enough to produce immediate death of tissues . Add suffix it is to the latin name : Examples: Glossitis = inflammation of the tongue Gastritis = Inflammation of the stomach Hepatitis = Inflammation of the liver Cholecystitis = inflammation of the gall bladder Cystitis = inflammation of the urinary bladder . Few exceptions are : Pneumonia = inflammation of the lung Pleurisy = inflammation of the pleura . Causes of inflammation : 1- Physical agents as trauma , heat , cold , electricity and irradiation 2- Chemical agents as acids , alkalies and irritant oils 3- Living agents as bacteria , viruses , fungi and parasites 4- Immunological disturbances Types of inflammation : a- Acute and subacute b- Chronic According to the onset and duration of inflammation . ACUTE INFLAMMATION Phenomena of acute inflammation A- Vascular changes 1- Momentary vasoconstriction ( lasts few second – of no practical value ) 2- Vasodilatation in arterioles and later in venules and capillaries ( due to direct action of chemical mediators) leads to : increased quantity of blood flow to the affected area hyperemia leading to redness and hotness . B-Formation of inflammatory fluid exudate Definition : It is a protein rich fluid passing through the vessel wall into the interstitial tissue . It causes swelling of the area . Mecanism : Increased filtration pressure due to : 1- vasodilatation of arterioles and capillaries ( increased blood flow )leading to increased capillary blood pressure 2- Increased capillary permeability ( gaps between the endothelium) leads to passage of protein from capillaries 3- Increased osmotic pressure in tissue spaces ( due to break down of necrotic cells into large number of small molecules (suction action) Composition : 1- Hematogenous part (plasma and leucocytes ) 2- Histogenous (cellular part ) histiocytes , plasma cells ,lymphocytss and mast cells ) 3- Protein content more than 3% 4- Specific gravity more than 1018 Functions : 1-Dilutrion and neutralization of bacterial toxins 2- It helps in localization of infection by formation of fibrin thread around the area of infection 3- The cells phagocytose microorganisms and secrete proteolytic enzymes which liquefy dead tissues and prepare the area for healing 4- Bring antibodies from the blood to the site of inflammation C- Margination and emigration of leucocytes Casuses : 1- Hyperemia and Exudation of fluid leads to increased viscosity of blood ( hemoconcentration) 2- slow of blood stream ( vasodilatation and opening of new capillaries leads to distribution of the blood reaching the area among a large number of capillaries ) 3- Swelling of the endothelium which becomes sticky and offers mechanical resistance . So: Margination : Leucocytes leave the axial stream and arrange them selves at the periphery Emigration of leucocytes : At the same the gapes between the endothelial cells widened ( swollen endothelium). Leucocytes ( polymorphs and monocytes ) send pseudopodia and escape out side the blood vessels through these gaps . This process is controlled by cell adhesion molecules on both beutrophils and endothelium ,firstly selectin and then integrins ** Chemotaxis Definition : It means attraction of cells ( neutrophils and monocytes ) towards a chemical substance ( chemotactic agent ) as : - chemical substabnces released from damaged tissues - Fraction of the complement in the blood ( C5a) - Factors derived from sensitized lymphocytes ( lymphokines ) - Factors derived from pathogenic bacteria - Factors derived from neutrophils It is a selective mechanism according to the infective agent -Cocci attract polymorphonuclear leucocytes - Bacilli attract monocytes - Viruses attract lymphocytes -Parasites attract esinophils . Chemical mediators of acute inflammation Definition: These are chemical substances that require activation may be a- circulating in the plasma c- secreted by inflammatory cells Functions : They act in inflammation and produce a- vasodilatation b- Increased permeability of blood vessels c- Margination and emigration of leucocytes d- Chemotaxis Examples : 1- polypeptides as kallikrein and bradykinin from plasma 2- Activated complement fractions as C3 and C5 3- Prostaglandins as PGE2 secreated by polymorphs and other tissues 4- Vasoactive anmines as histamine from mast cells and serotonin from platelets 5- Lysosomal enzymes 6- Bacterial toxins . 7- Phagocytosis . Manifestations of acute inflammation : 1- Local : 1-Redness 2- Hotness 3-Swelling 4- Pain 5- Disturbance of functions 2-General a- Fever : causes : bacterial toxins and Interlukin produced from leucocytes which release PGE2 by the hypothalamus b-Toxic manifestations as headache , malaise , loss of appetite and rapid pulse c- Leucocytosis increase in the blood by leucocyte promoting factor produced by the necrotic tissue and by products of T lymphocytes . Cells of Inflammation 1- polymorphnuclear leucocyte - It is characteristic of acute inflammation - The main function is phagocytosis of microorganisms - When it is dead it becomes Pus cells 2-Lymphocytes : - Seen in chronic inflammation - Two types : a-B lymphocytes which form immunoglobulins b-T lymphocytes produce lymphokines 3- Plasma cells - most characteristic cell in chronic inflammation - They secrete and store immunoglobulines 4- Histiocytes - They are large cells with abundant cytoplasm and vesicular nuclei - Sites : in the connective tissue of most organs They are called macrophages - Function : a- Phagocytosis of microorganisms , foreign bodies , necrotic debris . b- They remove and prepare the damaged tissue for repair c- play important role in immune response d- produce many active substances as the complement 5-Esinophils - Seen in allergic and parasitic infestation attracted by esinophil chemotactic factor produced from activated mast cells Function : a- Release substance that antagonize histamine , serotonin and bradykinins b- Release enzymes which help immunoglobulins to kill parasites ( shistosomulae ) c- They are capable of phagocytosing antigen antibody complexes and reduce hypersensitivity reactions d- They may release some substances that exaggerate some allergic conditions as bronchial asthma. 6-Mast cells : They contain heparin , histamine and serotonin They play important role in allergic conditions . 7-Giant cells - Occur in chronic infections ( granuloma) as in tuberculosis - They are formed by fusion of histiocytes and monocytes or nuclear division without cytoplasmic division - They are phagocytic cells -Types : 1-Langhans giant cells( in Tuberculosis ) , 2-foreign body giant cells( in chronic inflammation) , 3-megakaryocytes( In bone marrow) , 4-osteoclasts( in bone) , 5-tumour giant cells(in malignant tumours ) , 6-Hodgkins giant cells (in Hodgikins lymphoma) and 7-Aschoff giant cells ( in rheumatic fever ) 8- Touton giant cells ( in xanthomas ) Phagocytosis : Definition : Its an active process by which phagocytic cells are capable of engulfing and destroy microorganisms , dead tissues and foreign substances Aim : defensive mechanism mainly in bacterial infections Cells of phagocytosis : a- polymorphs b- Tissue histiocytes and blood monocytes They are helped by antibodies called opsonins ( coat the microorganisms) . Killing bacteria is achieved by : Action of hydrogen peroxide , myeloperoxidase system , toxic free oxygen radicals , hydrolytic enzymes of lysosomes and macrophage activating factor . 3- Spread of infection by a- Direct spread b- Lymphatics causing lymphangitis and lymphadenitis c- Blood causing toxemia or septicemia d- Septic thrombophlebitis causing pyemia 4- Suppuration if the inflammation is not suppurative from the start 5- Chronicity due to persistence of the causative agent .
Posted on: Fri, 31 Oct 2014 09:33:56 +0000
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