Inflammation (PDF)

INFLAMMATION  LEARNING OBJECTIVES:  At the end of the chapter the student is expected to 1. Know the causes of inflammation 2. Understand the process of inflammations 3. Comprehend the etiopathogeneses of granulomatous inflammations 4. Contrast the differences between acute and...

INFLAMMATION  LEARNING OBJECTIVES:  At the end of the chapter the student is expected to 1. Know the causes of inflammation 2. Understand the process of inflammations 3. Comprehend the etiopathogeneses of granulomatous inflammations 4. Contrast the differences between acute and chronic inflammations  Introduction Inflammation is defined as the local response of living mammalian tissues to injury due to any agent. Body defense reaction – eliminate or limit the spread of injurious agent INTRODUCTION  Definition: Inflammation is a local response (reaction) of living vasculaized tissues to endogenous and exogenous stimuli.  The term is derived from the Latin "inflammare" meaning to burn.  Inflammation is fundamentally destined to localize and eliminate the causative agent and to limit tissue injury.  Thus, inflammation is a physiologic (protective) response to injury, an observation made by Sir John Hunter in 1794 concluded: “inflammation is itself not to be considered as a disease but as a salutary operation consequent either to some violence or to some diseases”. Causes Causes of inflammation are apparently causes of diseases such as  physical agents - mechanical injuries, alteration in temperatures and pressure, radiation injuries.  chemical agents- including the ever increasing lists of drugs and toxins.  biologic agents (infectious)- bacteria,viruses,fungi, parasites  immunologic disorders- hypersensitivity reactions, autoimmunity, immunodeficiency states etc  genetic/metabolic disorders- examples gout, diabetes mellitus etc How is Inflammation distinct from Infection ??  Inflammation Protective response by the body to variety of etiologic agents, while infection is invasion into the body by harmful microbes and their resultant ill-effects by toxins 2 basic processes with some overlapping – early inflammatory response – later followed by healing Sometimes it causes considerable harm to the body as well anaphylaxis to bites by insects or reptiles, drugs, toxins, atherosclerosis, chronic rheumatoid arthritis, fibrous bands Adhesions in intestinal obstruction Nomenclature  The nomenclatures of inflammatory lesion are usually indicated by the suffix 'itis’.  Thus, inflammation of the appendix is called appendicitis and that of meninges as meningitis, etc.…  However, like any rule, it has its own exceptions examples pneumonia, typhoid fever, etc…. Classification  Inflammation is classified crudely based on duration of the lesion and histologic appearances into  acute and  chronic inflammation.  ACUTE INFLAMMATION Definition: the immediate and early response to injury or necrosis that occurs in a vascularized tissue Latin – inflammare = to set on fire Nomenclature: The term used to describe inflammation in different tissues employs the tissue name and the suffix “-itis” E.g.: pulpitis = inflammation of dental pulp tissue: - dental caries; - bacterial infections; - trauma (repeated dental procedures) gingivitis = inflammation of the gum tissue: - bacterial infections of the plaque  ACUTE INFLAMMATION Roles: Acute inflammation is the most important normal non-specific (innate) defense reaction aimed at: ▪ Removing the cause (microorganisms, foreign bodies) ▪ Repairing / limiting the damage to a certain area ▪ Clearing debris and prepare the area of injury for healing ▪ Interacting with components of the specific immune system  ACUTE INFLAMMATION Etiology: I. Non-specific factors: 1. Microorganisms: bacteria, viruses, fungi, parasites 2. Foreign bodies 3. Tissue destruction with formation of tissue debris through: → Mechanical damage: cuts, stubs, scratches → Chemical compounds: acids, alkali → Physical agents: cold, heat, radiation (UV, X-rays) → Endogenous causes: tumour cells, crystals of substances precipitated in the body II. Specific factors 1. Hypersensitivity reactions (when your immune system overreacts !) 2. Autoimmune diseases (when your immune system mistakenly attacks your own healthy cells !) ACUTE INFLAMMATION  Acute inflammation is an immediate and early response to an injurious agent and it is relatively of short duration, lasting for minutes, several hours or few days.  It is characterized by exudation of fluids and plasma proteins and the emigration of predominantly neutrophilic leucocytes to the site of injury.  SIGNS OF INFLAMMATION 4 cardinal signs (Celsus) – rubor (redness); – tumor (swelling); – calor (heat); – dolor (pain) 5th sign functio laesa (loss of function) - Virchow facebook.com/trigemclasses facebook.com/trigemclasses ACUTE INFLAMMATION The five cardinal signs of acute inflammation are  Redness (rubor) which is due to dilation of small blood vessels within damaged tissue as it occurs in cellulitis.  Heat (calor) which results from increased blood flow (hyperemia) due to regional vascular dilation  Swelling (tumor) which is due to accumulation of fluid in the extravascular space which, in turn, is due to increased vascular permeability.  Pain (dolor), which partly results from the stretching & destruction of tissues due to inflammatory edema and in part from pus under pressure in as abscess cavity. Some chemicals of acute inflammation, including bradykinins, prostaglandins and serotonin are also known to induce pain.  Loss of function: The inflammed area is inhibited by pain while severe swelling may also physically immobilize the tissue. Cellulitis ACUTE INFLAMMATION Effects of acute inflammation: A. Beneficial effects  Dilution of toxins: The concentration of chemical and bacterial toxins at the site of inflammation is reduced by dilution in the exudate and its removal from the site by the flow of exudates from the venules through the tissue to the lymphatics.  Protective antibodies: Exudation results in the presence of plasma proteins including antibodies at the site of inflammation. Thus, antibodies directed against the causative organisms will react and promote microbial destruction by phagocytosis or complement-mediated cell lysis.  Fibrin formation: This prevents bacterial spread and enhances phagocytosis by leukocytes.  Plasma mediator systems provisions: The complement, coagulation, fibrinolytic, & kinin systems are provided to the area of injury by the process of inflammation ACUTE INFLAMMATION Effects of acute inflammation: A. Beneficial effects  Cell nutrition: The flow of inflammatory exudates brings with it glucose, oxygen and other nutrients to meet the metabolic requirements of the greatly increased number of cells. It also removes their solute waste products via lymphatic channels.  Promotion of immunity: Micro-organisms and their toxins are carried by the exudates, either free or in phagocytes, along the lymphaics to local lymph nodes where they stimulate an immune response with the generation of antibodies and cellular immune mechanisms of defence. ACUTE INFLAMMATION Effects of acute inflammation: B. Harmful effects ❑ Tissue destruction Inflammation may result in tissue necrosis and the tissue necrosis may, in turn, incite inflammation. ❑ Swelling: The swelling caused by inflammation may have serious mechanical effects at certain locations. Examples include acute epiglottitis with interference in breathing; Acute meningitis and encephalitis with effects of increased intracranial pressure. ❑ Inappropriate response: The inflammatory seen in hypersensitivity reactions is inappropriate (i.e. exaggerated). CHRONIC INFLAMMATION  Definition: Chronic inflammation can be defined as a prolonged inflammatory process (weeks or months) where an active inflammation, tissue destruction and attempts at repair are proceeding simultaneously. CHRONIC INFLAMMATION  Causes of chronic inflammation:  1. Persistent infections  Certain microorganisms associated with intracellular infection such as tuberculosis, leprosy, certain fungi etc characteristically cause chronic inflammation.  These organisms are of low toxicity and evoke delayed hypersensitivity reactions.  2. Prolonged exposure to nondegradable but partially toxic substances either endogenous lipid components which result in atherosclerosis or exogenous substances such as silica, asbestos. CHRONIC INFLAMMATION  Causes of chronic inflammation:  3. Progression from acute inflammation: Acute inflammation almost always progresses to chronic inflammation following: a. Persistent suppuration as a result of uncollapsed abscess cavities, foreign body materials (dirt, cloth, wool, etc), sequesterum in osteomylitis, or a sinus/fistula from chronic abscesses.  4. Autoimmuniy. Autoimmune diseases such as rheumatoid arthritis and systemic lupus erythematosis are chronic inflammations from the outset  TYPES OF INFLAMMATION Mainly of 2 types i.e. acute and chronic Acute Inflammation – short duration – represents the early body reaction- followed by healing Chronic inflammation – longer duration – causative agent of acute inflammation persists for a long time Another variant, Chronic active inflammation : stimulus is such that it induces chronic inflammation from the beginning facebook.com/trigemclasses Components of Acute and Chronic Inflammatory responses facebook.com/trigemclasses