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Micro Final (got the best grade in class)

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Biological Sciences
BIOL 2051
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Chapter 23 Human Microflora and Nonspecific Host Defenses Human MicrofloraoHumans colonized by many microbesoNormal flora Commensal mutualistic organismsoMicrobe populations change constantlyVary with type of tissueconditionsPh moisture other microbespresentIntestinal flora varies with food eatenCan cause disease if reach abnormal locationoMetagenomecollective genome of all microbes in and on bodyNormal Human FloraoThere are billions of microbial cells living in and on the human body majority are unknown and have never been grown in laboAreas which should be sterileInternal organsBloodCerebrospinal fluidoSites where bacteria are normally foundSkinOral cavityGastrointestinal tractRespiratory tractUrogenital tractoSee Fig 231oHuman Microflora SkinSkin is difficult to colonizeDry salty acidic protective oils lysozymeMicrobes grow mostly in moist areasunderarms genitals etcAssociated with sebaceous oil glandsapocrine sweat glands pH 46Factors that affect types of normal flora weather age personal hygieneMicrobes commonly associated with the skinMost are G bacteriaoStaphylococcusoStreptococcusoPropionibacterium Gramanaerobic rodsPropionibacterium acnes can cause acneoBacillusSome yeastsoCandidaoHuman Microflora EyeMost inhibited by lysozymecontinual rinsing of conjunctiva eye surfaceSometimes S epidermidis and some Gram rods can temporarily reside in eye without causing infectionPinkeyeconjunctivitis can be caused by several types of bacteriavirusesoHuman Microflora MouthBacteria in the mouth prior to tooth formation are mainly aerotolerant anaerobes such as streptococcusLactobacillus well as some yeastAfter teeth emerge anaerobic areas between teeth and gums support anaerobes such as Prevotella Fusobacteriumand Teeth and gingival crevices colonized by over 500 species of bacteriaAcidic glycoproteins in saliva form a layer on teeth providing a firm attachment site for microbes usually Streptococcus speciesExtensive growth of these microbes results in thick bacterial layers called dental plaqueDental procedures can cause organisms to enter the bloodstream and causes organisms to enter the bloodstream and cause bacteremia which is quickly cleared by immune systemIn patients with mitral valve prolapse heart murmur bacteria can be trapped in defective valve and form vegetations bacterial cells glycocalyx fibrin subacute bacterial endocarditis Microflora of dental plaques make acids that decalcify tooth enamelresults in dental caries tooth decay cavitiesTooth surfaces in and near the gingival crevice where food particles remain are common sites of tooth decayFlossDiets high in sucrose are cariogeniccavity causingLactic acid bacteria ferment the sucrose to lactic acidStreptococcus mutans producesdextran polysaccharide used for attachment to tooth surface only when sucrose is presentDiets containing fluoride during formation of tooth enamel make teeth more resistant to tooth decayIncorporation of fluoride into the calcium phosphate crystal matrix increases resistance to decalcificationoHuman Microflora Respiratory TractUpper respiratory tract nasopharynx oral cavitythroatMost bacteria that are breathed in are trapped in mucusAre many opportunistic pathogens in nasopharynxOpportunistic pathogens which can be found in the nasopharynxoStaphylococcusCauses sinusear infectionsoStreptococcusCauses sinus infectionsbronchitisoStreptococcus Causes sinus infectionsstrep throatoCorynebacterium diphtheriaeCauses diphtheria severe childhood illnessLower respiratory tract Bacteria are not normally found in lower respiratory tractLower respiratory tract is lined with cilia which push bacteriadust particles up where they are caught in mucussaliva mucociliaryNormal flora of the gastrointestinal tractoHuman Microflora StomachpH2Only acidtolerant bacteria can colonize stomach wallex Heliobacter pylori peptic ulcersVery few bacteria are found in stomach fluidsoHuman Microflora Small Intestine of bacteria increases down through small intestinedue to rising pHDuodenum few bacteria due to stomach acids pancreatic secretions and bile mainly Gramcocci and bacilliJejunum Enterococcus LactobacillusIleum microbiota reflects that of large intestine large number of Bacteroidesfacultative aerobes like EcolioHuman Microflora Large IntestineFermentation vessel many bacteria 300 species mostly anaerobesmost have never been culturedCommonly 10 11 bacterial cellsgram of intestinal contentsSmall number of facultative aerobes E coliconsume oxygen which allows obligate anaerobes to growBacteria ferment ingested food into products we can absorb we absorb 15 of our caloric intake this way studies on sets of twins where one was obese and one lean showed drastic differences in their gut microbiomesProvide nutrients inhibit pathogensCommon intestinal flora
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