Blood

FunctionsTransportation: water, gases, nutrients, hormones, enzymes, electrolytes, wastesRegulation: pH, temperature, water balance Protection: blood clotting, defense: phagocytic cells, interferons, complement

CompositionA connective tissue with components readily seen when blood is centrifuged:Plasma(~55%): soluble materials (mostly water); lighter (top of tube)Formed elements (~45%): cells (heavier so at bottom of tube) Mostly red blood cells (RBCs)Buffy coat: site of white blood cells (WBCs), platelets

Composition

Plasma: Liquid Portion of BloodWater: 91.5% Plasma proteins: 7%Albumin (54%): function in osmosis; carriers Globulins (38%): serve as antibodiesFibrinogen (7%): important in clottingOther: 1.5%Electrolytes, nutrients, gases, hormones, vitamins, waste products

Formed ElementsI. Red Blood Cells (RBCs)II. White blood cells (WBCs)Granular leukocytesNeutrophilsEosinophilsBasophilsAgranular leukocytesLymphocytes and natural killer (NK) cellsMonocytesIII Platelets

Formation of Blood Cells

Erythrocytes (RBCs)Hemoglobin (red pigment)Carries 98.5% of O2 and 23% of CO2 RBC count: about 5 million/lMale: 5.4 million cells/l; female: 4.8 million/lStructure of mature RBCNo nucleus/DNA so RBCs live only 3 to 4 mosLack of nucleus causes biconcave disc shape with extensive plasma membraneProvides for maximal gas exchangeIs flexible for passing through capillaries

White Blood Cells (WBCs or Leukocytes)Appear white because lack hemoglobinNormal WBC count: 5,000-10,000/lWBC count usually increases in infectionTwo major classes based on presence or absence of granules (vesicles) in themGranular: neutrophils, eosinophils, basophilsNeutrophils usually make up 2/3 of all WBCsAgranular: lymphocytes, monocytes Major function: defense againstInfection and inflammationAntigen-antibody (allergic) reactions

WBC Life SpanWBCs: 5000-10,000 WBCs/l blood

Life span: typically a few hours to daysAbnormal WBC countsLeukocytosis: high WBC count in response to infection, exercise, surgeryLeukopenia: low WBC count

Platelets megakaryocytes Normal count: 150,000-400,000/l bloodFunctionsPlug damaged blood vesselsPromote blood clottingLife span 59 days

Blood Groups and Blood TypesRBCs have antigens (agglutinogens) on their surfacesEach blood group consists of two or more different blood typesTwo examples: ABO group has types A, B, AB, ORh group has type Rh positive (Rh+), Rh negative (Rh) Blood types in each person are determined by genetics

ABO GroupTwo types of antigens on RBCs: A or BType A has only A antigenType B has only B antigenType AB has both A and B antigensType O has neither A nor B antigen

Typically blood has antibodies in plasmaThese can react with antigensTwo types: anti-A antibody or anti-B antibodyBlood lacks antibodies against own antigensType A blood has anti-B antibodies (not anti-A)Type AB blood has neither anti-A nor anti-B antibodies

ABO Group

Rh Blood GroupName Rh: antigen found in rhesus monkeyRh blood typesIf RBCs have Rh antigen: Rh+If RBCs lack Rh antigen: Rh

Antibodies develop in Rh- persons after first exposure to Rh+ blood in transfusion (or pregnancy hemolytic disease of newborn)

TransfusionsIf mismatched blood (wrong blood type) given, antibodies bind to antigens on RBCs hemolyze RBCsType AB called universal recipients because have no anti-A or anti-B antibodies so can receive any ABO type blood Type O called universal donors because have neither A nor B antigen on RBCs so can donate to any ABO type Misleading because of many other blood groups that must be matched