Chapter 19: The Cardiovascular System: The Blood
Copyright 2009, John Wiley & Sons, Inc.
Blood
Liquid connective tissue3 general functions
Transportation
Gases, nutrients, hormones, waste products
Regulation
pH, body temperature, osmotic pressure
Protection
Clotting, white blood cells, proteins
Copyright 2009, John Wiley & Sons, Inc.
Components of Blood
Blood plasma water liquid extracellular matrix91.5% water, 8.5% solutes (primarily proteins)Hepatocytes synthesize most plasma proteinsAlbumins, fibrinogen, antibodiesOther solutes include electrolytes, nutrients, enzymes, hormones, gases and waste productsFormed elements cells and cell fragmentsRed blood cells (RBCs)White blood cells (WBCs)Platelets
Copyright 2009, John Wiley & Sons, Inc.
Copyright 2009, John Wiley & Sons, Inc.
Formed Elements of Blood
Copyright 2009, John Wiley & Sons, Inc.
Formation of Blood Cells
Negative feedback systems regulate the total number of RBCs and platelets in circulationAbundance of WBC types based of response to invading pathogens or foreign antigensHemopoiesis or hemotopoiesisRed bone marrow primary sitePluripotent stem cells have the ability to develop into many different types of cells
Copyright 2009, John Wiley & Sons, Inc.
Copyright 2009, John Wiley & Sons, Inc.
Formation of Blood Cells
Stem cells in bone marrowReproduce themselvesProliferate and differentiateCells enter blood stream through sinusoidsFormed elements do not divide once they leave red bone marrowException is lymphocytes
Copyright 2009, John Wiley & Sons, Inc.
Formation of Blood Cells
Pluripotent stem cells produceMyeloid stem cellsGive rise to red blood cells, platelets, monocytes, neutrophils, eosinophils and basophilsLymphoid stem cells give rise toLymphocytesHemopoietic growth factors regulate differentiation and proliferationErythropoietin RBCsThrombopoietin plateletsColony-stimulating factors (CSFs) and interleukins WBCs
Copyright 2009, John Wiley & Sons, Inc.
Red Blood Cells/ Erythrocytes
Contain oxygen-carrying protein hemoglobinProduction = destruction with at least 2 million new RBCs per secondBiconcave disc increases surface areaStrong, flexible plasma membraneGlycolipids in plasma membrane responsible for ABO and Rh blood groupsLack nucleus and other organellesNo mitochondria doesnt use oxygen
Copyright 2009, John Wiley & Sons, Inc.
Hemoglobin
Globin 4 polypeptide chainsHeme in each of 4 chainsIron ion can combine reversibly with one oxygen moleculeAlso transports 23% of total carbon dioxideCombines with amino acids of globinNitric oxide (NO) binds to hemoglobinReleases NO causing vasodilation to improve blood flow and oxygen delivery
Copyright 2009, John Wiley & Sons, Inc.
Shapes of RBC and Hemoglobin
Copyright 2009, John Wiley & Sons, Inc.
Red Blood Cells
RBC life cycleLive only about 120 daysCannot synthesize new components no nucleusRuptured red blood cells removed from circulation and destroyed by fixed phagocytic macrophages in spleen and liverBreakdown products recycledGlobins amino acids reusedIron reusedNon-iron heme ends as yellow pigment urobilin in urine or brown pigment stercobilin in feces
Copyright 2009, John Wiley & Sons, Inc.
Formation and Destruction of RBCs
Copyright 2009, John Wiley & Sons, Inc.
Copyright 2009, John Wiley & Sons, Inc.
Erythropoiesis
Starts in red bone marrow with proerythroblastCell near the end of development ejects nucleus and becomes a reticulocyteDevelop into mature RBC within 1-2 daysNegative feedback balances production with destructionControlled condition is amount of oxygen delivery to tissuesHypoxia stimulates release of erythropoietin
Copyright 2009, John Wiley & Sons, Inc.
White Blood Cells/ Leukocytes
Have nucleiDo not contain hemoglobinGranular or agranular based on staining highlighting large conspicuous granulesGranular leukocytesNeutrophils, eosinophils, basophilsAgranular leukocytesLymphocytes and monocytes
Copyright 2009, John Wiley & Sons, Inc.
Types of White Blood Cells
Copyright 2009, John Wiley & Sons, Inc.
Functions of WBCs
Usually live a few daysExcept for lymphocytes live for months or yearsFar less numerous than RBCsLeukocytosis is a normal protective response to invaders, strenuous exercise, anesthesia and surgeryLeukopenia is never beneficialGeneral function to combat invaders by phagocytosis or immune responses
Copyright 2009, John Wiley & Sons, Inc.
Emigration of WBCs
Many WBCs leave the bloodstreamEmigration (formerly diapedesis)Roll along endotheliumStick to and then squeeze between endothelial cellsPrecise signals vary for different types of WBCs
Copyright 2009, John Wiley & Sons, Inc.
WBCs
Neutrophils and macrophages are active phagocytesAttracted by chemotaxisNeutrophils respond most quickly to tissue damage by bacteriaUses lysozymes, strong oxidants, defensinsMonocytes take longer to arrive but arrive in larger numbers and destroy more microbesEnlarge and differentiate into macrophages
Copyright 2009, John Wiley & Sons, Inc.
WBCs
Basophila leave capillaries and release granules containing heparin, histamine and serotonin, at sites of inflammationIntensify inflammatory reactionInvolved in hypersensitivity reactions (allergies)Eosinophils leave capillaries and enter tissue fluidRelease histaminase, phagocytize antigen-antibody complexes and effective against certain parasitic worms
Copyright 2009, John Wiley & Sons, Inc.
Lymphocytes
Lymphocytes are the major soldiers of the immune systemB cells destroying bacteria and inactivating their toxinsT cells attack viruses, fungi, transplanted cells, cancer cells and some bacteriaNatural Killer (NK) cells attack a wide variety of infectious microbes and certain tumor cells
Copyright 2009, John Wiley & Sons, Inc.
Platelets/ Thrombocytes
Myeloid stem cells develop eventually into a megakaryocyteSplinters into 2000-3000 fragmentsEach fragment enclosed in a piece of plasma membraneDisc-shaped with many vesicles but no nucleusHelp stop blood loss by forming platelet plugGranules contain blood clot promoting chemicalsShort life span 5-9 days
Copyright 2009, John Wiley & Sons, Inc.
Stem cell transplants
Bone marrow transplantRecipient's red bone marrow replaced entirely by healthy, noncancerous cells to establish normal blood cell countsTakes 2-3 weeks to begin producing enough WBCs to fight off infectionsGraft-versus-host-disease transplanted red bone marrow may produce T cells that attack host tissuesCord-blood transplantStem cells obtained from umbilical cord shortly before birthEasily collected and can be stored indefinitelyLess likely to cause graft-versus-host-disease
Copyright 2009, John Wiley & Sons, Inc.
Hemostasis
Sequence of responses that stops bleeding3 mechanisms reduce blood loss
Vascular spasm
Smooth muscle in artery or arteriole walls contracts
Platelet plug formation
Platelets stick to parts of damaged blood vessel, become activated and accumulate large numbers
Blood clotting (coagulation)
Copyright 2009, John Wiley & Sons, Inc.
Platelet Plug Formation
Copyright 2009, John Wiley & Sons, Inc.
Copyright 2009, John Wiley & Sons, Inc.
Blood Clotting
Blood clotting
Serum is blood plasma minus clotting proteinsClotting series of chemical reactions culminating in formation of fibrin threadsClotting (coagulation) factors Ca2+, several inactive enzymes, various molecules associated with platelets or released by damaged tissues
Copyright 2009, John Wiley & Sons, Inc.
3 Stages of Clotting
Extrinsic or intrinsic pathways lead to formation of prothrombinase
Prothrombinase converts prothrombin into thrombin
Thrombin converts fibrinogen (soluble) into fibrin (insoluble) forming the threads of the clot
Copyright 2009, John Wiley & Sons, Inc.
Copyright 2009, John Wiley & Sons, Inc.
Blood Clotting
Extrinsic pathwayFewer steps then intrinsic and occurs rapidlyTissue factor (TF) or thromboplastin leaks into the blood from cells outside (extrinsic to) blood vessels and initiates formation of prothrombinaseIntrinsic pathwayMore complex and slower than extrinsicActivators are either in direct contact with blood or contained within (intrinsic to) the bloodOutside tissue damage not neededAlso forms prothrombinase
Copyright 2009, John Wiley & Sons, Inc.
Blood Clotting: Common pathway
Marked by formation of prothrombinaseProthrombinase with Ca2+ catalyzes conversion of prothrombin to thrombinThrombin with Ca2+ converts soluble fibrinogen into insoluble fibrinThrombin has 2 positive feedback effectsAccelerates formation of prothrombinaseThrombin activates plateletsClot formation remains localized because fibrin absorbs thrombin and clotting factor concentrations are low
Copyright 2009, John Wiley & Sons, Inc.
Blood Groups and Blood Types
Agglutinogens surface of RBCs contain genetically determined assortment of antigensBlood group based on presence or absence of various antigens At least 24 blood groups and more than 100 antigensABO and Rh
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ABO Blood Group
