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An overview of the body's defense mechanisms against pathogens, focusing on the three lines of defense: the physical barriers of the skin and mucous membranes, the innate immune response, and the adaptive immune response. It covers the functions and examples of each line of defense, as well as the role of specific immune cells and chemicals in protecting the body.
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uu Nonspecific Resistance:Nonspecific Resistance: Defenses that protectDefenses that protect againstagainst allall pathogens.pathogens. uu Specific Resistance:Specific Resistance: Protection againstProtection against specificspecific pathogens.pathogens.
Skin and Mucous MembranesSkin and Mucous Membranes
uu Two layers: Outer epithelial and inner connective layer.Two layers: Outer epithelial and inner connective layer.
uu Epithelial layer secretes mucus which maintains moistEpithelial layer secretes mucus which maintains moist surfaces.surfaces. uu Although they inhibit microbial entry, they offer lessAlthough they inhibit microbial entry, they offer less protection than skin.protection than skin. uu Several microorganisms are capable of penetratingSeveral microorganisms are capable of penetrating mucous membranes:mucous membranes: FF PapillomavirusPapillomavirus FF Treponema pallidumTreponema pallidum FF EE nteroinvasiventeroinvasive E.E. colicoli FF Entamoeba histolyticaEntamoeba histolytica
3.3. LacrimalLacrimal apparatusapparatus: Continual washing and: Continual washing and blinking prevents microbes from settling on theblinking prevents microbes from settling on the eye surface.eye surface.
uu SebumSebum: Oily substance produced by: Oily substance produced by sebaceous glands that forms a protective layersebaceous glands that forms a protective layer over skin. Contains unsaturated fatty acidsover skin. Contains unsaturated fatty acids which inhibit growth of certain pathogenicwhich inhibit growth of certain pathogenic bacteria and fungi.bacteria and fungi. uu pHpH: Low, skin pH usually between 3 and 5.: Low, skin pH usually between 3 and 5. Caused by lactic acid and fatty acids.Caused by lactic acid and fatty acids. uu PerspirationPerspiration: Produced by sweat glands.: Produced by sweat glands. ContainsContains lysozymelysozyme and acids.and acids. uu LysozymeLysozyme: Enzyme that breaks down gram: Enzyme that breaks down gram-- positive cell walls. Found in nasal secretions,positive cell walls. Found in nasal secretions, saliva, and tears.saliva, and tears.
uu Gastric JuiceGastric Juice : Mixture of hydrochloric acid,: Mixture of hydrochloric acid, enzymes, and mucus. pH between 1.2 to 3enzymes, and mucus. pH between 1.2 to 3 kills many microbes and destroys most toxins.kills many microbes and destroys most toxins. Many enteric bacteria are protected by foodMany enteric bacteria are protected by food particles.particles. FF Helicobacter pyloriHelicobacter pylori neutralizes stomach acid andneutralizes stomach acid and can grow in the stomach, causing gastritis andcan grow in the stomach, causing gastritis and ulcers.ulcers. uu TransferrinsTransferrins: Iron: Iron--binding proteins in bloodbinding proteins in blood which inhibit bacterial growth by reducingwhich inhibit bacterial growth by reducing available iron.available iron.
Triggered by tissue damage due to infection, heat,Triggered by tissue damage due to infection, heat, wound, etc.wound, etc. Four Major Symptoms of Inflammation:Four Major Symptoms of Inflammation: 1.1. RednessRedness
1.1. VasodilationVasodilation: Increase in diameter of blood: Increase in diameter of blood vessels.vessels. Triggered by chemicals released by damaged cells:Triggered by chemicals released by damaged cells: histamine,histamine, kininskinins,, prostaglandinsprostaglandins, and, and leukotrienesleukotrienes..
Phagocytes are attracted to site of infectionPhagocytes are attracted to site of infection throughthrough chemotaxischemotaxis.. Phagocytes destroy microbes, as well as dead andPhagocytes destroy microbes, as well as dead and damaged host cells.damaged host cells.
I. Complement SystemI. Complement System: Large group of serum: Large group of serum proteins that participate in theproteins that participate in the lysislysis of foreignof foreign cells, inflammation, andcells, inflammation, and phagocytosisphagocytosis.. Two mechanisms of complement activation:Two mechanisms of complement activation:
1.1. CytolysisCytolysis: Due to the formation of a: Due to the formation of a membranemembrane attackattack complexcomplex (MAC) which produces lesions in(MAC) which produces lesions in microbial membranes.microbial membranes. 2.2. InflammationInflammation: Complement components (C3a): Complement components (C3a) trigger the release of histamine, which increasestrigger the release of histamine, which increases vascular permeability.vascular permeability. 3.3. OpsonizationOpsonization: Complement components (C3b): Complement components (C3b) bind to microbial surface and promotebind to microbial surface and promote phagocytosisphagocytosis.. 4.4. Inactivation of ComplementInactivation of Complement: Regulatory proteins: Regulatory proteins limit damage to host cells that may be caused bylimit damage to host cells that may be caused by complement.complement.