Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsBlood Supply to the Liver[Question]: Since the liver receives DEOXYGENATEDblood from the small intestine, how do liver cells getenough oxygen to carry out cellular respiration?[Answer]: The liver receives a blood supply from twosources:-The hepatic artery delivers oxygenated blood fromthe general circulation.-The hepatic portal vein delivers deoxygenated bloodfrom the small intestine containing nutrients.Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsBlood Supply to the Liver• 75% of the blood entering the liver is venous blood from thehepatic portal vein (deoxygenated and nutrient-rich)• The remaining 25% of the blood supply to the liver is arterialblood from the hepatic artery (oxygenated)• Terminal branches of the hepatic portal vein and hepatic arteryempty together and mix as they enter the liver (i.e., bloodenters partially oxygenated and nutrient-rich)• All blood exits the liver via the hepatic vein and returns to theheart, now deoxygenated, detoxified, and containing normal(homeostatic) nutrient levels(Sources: http://www.geocities.com/mamablondie/liver.html,http://www.nottingham.ac.uk/nursing/sonet/rlos/bioproc/liveranatomy/2.html)LE 43-2Invadingmicrobes(pathogens)External defensesSkinMucous membranesSecretionsINNATE IMMUNITYRapid responses to abroad range of microbesACQUIRED IMMUNITYSlower responses tospecific microbesInternal defensesPhagocytic cellsInflammatory responseHumoral response(antibodies)Antimicrobial proteinsNatural killer cellsCell-mediated response(cytotoxiclymphocytes)Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsExternal Defenses• Skin and mucous membranes are physicalbarriers to entry of microorganisms and viruses• Mucous membrane cells produce mucus, aviscous fluid that traps microbes and otherparticles• In the trachea, ciliated epithelial cells sweepmucus and any entrapped microbes upward,preventing microbes from entering the lungsLE 43-310 µmCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Secretions of the skin and mucous membranesprovide an environment hostile to microbes• Secretions give the skin a pH between 3 and 5,acidic enough to prevent colonization of manymicrobes• Skin secretions include proteins such aslysozyme, which digests bacterial cell wallsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsInternal Cellular and Chemical Defenses• Internal cellular defenses depend mainly onphagocytosis• White blood cells called phagocytes ingestmicroorganisms and initiate inflammationLE 43-13 µmLE 43-4PseudopodiaMicrobesMACROPHAGELysosomecontainingenzymesVacuoleCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Macrophages, a type of phagocyte, migratethrough the body and are found in organs of thelymphatic system• The lymphatic system defends against pathogensLE 43-5AdenoidTonsilLymphnodesPeyer’s patches(small intestine)SpleenAppendixLymphaticvesselsLymphnodeMasses oflymphocytes andmacrophagesLymphaticvesselBloodcapillaryTissuecellsLymphaticcapillaryInterstitialfluidCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsAntimicrobial Proteins• Proteins function in innate defense by attackingmicrobes directly or impeding their reproduction• About 30 proteins make up the complementsystem, which causes lysis of invading cells andhelps trigger inflammation• Interferons provide innate defense against virusesand help activate macrophagesCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsInflammatory Response• In local inflammation, histamine and otherchemicals released from injured cells promotechanges in blood vessels• These changes allow more fluid, phagocytes, andantimicrobial proteins to enter tissuesLE 43-6PathogenPinChemical signalsCapillaryPhagocytic cellsMacrophageRed blood cellBloodclottingelementsBlood clotPhagocytosisCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsNatural Killer Cells• Natural killer (NK) cells attack virus-infected bodycells and cancer cells• They trigger apoptosis in the cells they attackCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsInvertebrate Immune Mechanisms• Many invertebrates defend against infection bymany of the same mechanisms in the vertebrateinnate
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