Blood Chapter 8

Functions of Blood Transports oxygen and nutrients to cells Carries carbon dioxide and wastes away from cells Helps stabilize internal pH Carries infection-fighting cells Helps equalize temperature

Blood Volume and Composition Plasma –50-60 percent of volume –Water, plasma proteins, dissolved ions and molecules Cellular portion –40-50 percent of volume –Red cells, white cells, and platelets

Plasma Mostly water Main plasma protein is albumin Other proteins, including hormones Ions, glucose and other simple sugars, amino acids, various communication molecules, and dissolved gases

Erythrocytes (Red Cells) Most numerous cells in the blood Transport oxygen and carbon dioxide Colored red by oxygen-binding pigment (hemoglobin) Have no nucleus when mature

Leukocytes (White Cells) Function in housekeeping and defense Cell types Basophils EosinophilsB lymphocytes NeutrophilsT lymphocytes Macrophages NK cells Dendritic cellsMast cells

Platelets Membrane-bound cell fragments Derived from megakaryocytes, which arise from stem cells Release substances that initiate blood clotting

Oxygen Transport Oxygen binds to heme group of hemoglobin Forms oxyhemoglobin Binding affected by –Oxygen concentration –Temperature –pH heme group

Life Cycle of Red Blood Cells Stem cell gives rise to nucleated “pre-erythrocyte” that synthesizes hemoglobin Once filled with hemoglobin, nucleus is expelled Cell is now an erythrocyte and will function for about 120 days

ABO Blood Type Type A red cells have one type of marker at surface Type B red cells have a different type of marker Type AB cells have both markers Type O cells have neither marker

Blood Type in Transfusions Require that donor and recipient have same blood type If bloods of incompatible types are mixed, recipient’s immune system will attack and destroy donor cells Agglutination reaction

ABO and Transfusions

Rh Blood Type Based on presence or absence of Rh factor on red cells Can cause problems during pregnancy –if mother is Rh negative –has previously carried Rh positive child –is carrying fetus that is Rh positive Mother’s antibodies can attack fetal cells

Hemostasis Blood vessel spasm Platelet plug formation Blood coagulation Enzymes activate factor X, forming prothrombinase Blood Clot Prothrombinase converts enzyme precursor to thrombin Thrombin converts fibrinogen to insoluble threads (fibrin) Fibrin forms net that entangles blood cells, platelets

Intrinsic and Extrinsic Triggers Intrinsic clotting mechanism gets under way when a protein in the blood plasma is activated Extrinsic clotting mechanism is triggered by the release of enzymes and other substances by damaged blood vessels or from the surrounding tissues

Blood Disorders Anemias Leukemias Mononucleosis