Chapter 14 The Cardiovascular System: Blood Copyright 2010, John Wiley & Sons, Inc. Functions Transportation: water, gases, nutrients, hormones, enzymes, electrolytes, wastes, heat Regulation: pH, temperature, water balance Protection: blood clotting, defense: phagocytic cells, interferons, complement Copyright 2010, John Wiley & Sons, Inc. Composition A connective tissue with components readily seen when blood is centrifuged: Plasma(~55%): soluble materials (mostly water); lighter so at top of tube Formed elements (~45%): cells (heavier so at bottom of tube) Mostly red blood cells (RBCs) Percent of blood occupied by RBCs = hematocrit (Hct) Normal hematocrit value: 42-47% Females: 38 to 46%; males: 40 to 54% Buffy coat: site of white blood cells (WBCs), platelets Copyright 2010, John Wiley & Sons, Inc. Composition Copyright 2010, John Wiley & Sons, Inc. Composition Copyright 2010, John Wiley & Sons, Inc. Plasma: Liquid Portion of Blood Water: 91.5% Plasma proteins: 7% Albumin (54%): function in osmosis; carriers Globulins (38%): serve as antibodies Fibrinogen (7%): important in clotting Other: 1.5% Electrolytes, nutrients, gases, hormones, vitamins, waste products Copyright 2010, John Wiley & Sons, Inc. Formed Elements I. Red Blood Cells (RBCs) II. White blood cells (WBCs) A. Granular leukocytes 1. Neutrophils 2. Eosinophils 3. Basophils B. Agranular leukocytes 1. Lymphocytes and natural killer (NK) cells 2. Monocytes III Platelets Copyright 2010, John Wiley & Sons, Inc. Formation of Blood Cells Called hemopoiesis or hematopoiesis Occurs throughout life In response to specific hormones, stem cells undergo a series of changes to form blood cells Pluripotent stem cells in red marrow Lymphoid stem cells lymphocytes (in lymphatic tissues) Myeloid stem cells all other WBCs, all RBCs, and platelets (in red bone marrow) Copyright 2010, John Wiley & Sons, Inc. Formation of Blood Cells Copyright 2010, John Wiley & Sons, Inc. Formation of Blood Cells Copyright 2010, John Wiley & Sons, Inc. Erythrocytes (RBCs) Hemoglobin (red pigment) RBC count: about 5 million/µl Carries 98.5% of O2 and 23% of CO2 Male: 5.4 million cells/µl; female: 4.8 million/µl Structure of mature RBC No nucleus/DNA so RBCs live only 3 to 4 mos Lack of nucleus causes biconcave disc shape with extensive plasma membrane Provides for maximal gas exchange Is flexible for passing through capillaries Copyright 2010, John Wiley & Sons, Inc. RBC Recycling Cleared by macrophages (liver and spleen) Recycled components Globin amino acids recycled to form proteins Heme broken down into: Fe Carried in blood by transferrin (“protein escort” of Fe) Recycled in bone marrow for forming synthesis of new hemoglobin; proteins and vitamin B12 required also Non-Fe portion of heme biliverdin bilirubin Bilirubin to liver bile helps absorb fats Intestinal bacteria convert bilirubin into other chemicals that exit in feces (stercobilin) or urine (urobilin) Copyright 2010, John Wiley & Sons, Inc. Formation and Destruction of RBC’s Circulation for about 120 days 7 3 Reused for protein synthesis Amino acids Globin 4 6 5 Fe3+ Fe3+ Transferrin 2 Heme Fe3+ Ferritin Transferrin Bilirubin 9 1 Red blood cell Biliverdin Bilirubin 11 10 death and phagocytosis Small intestine Kidney 13 12 Urobilin Macrophage in spleen, liver, or red bone marrow Bilirubin Urobilinogen Stercobilin Urine Liver + Globin + Vitamin B12 + Erythopoietin 8 Erythropoiesis in red bone marrow Bacteria Key: in blood Large 14 intestine Feces Copyright 2010, John Wiley & Sons, Inc. in bile RBC Synthesis: Erythropoiesis Develop from myeloid stem cells in red marrow Cells lose nucleus; are then released into bloodstream as reticulocytes These almost-mature RBCs develop into erythrocytes after 1-2 days in bloodstream High reticulocyte count (> normal range of 0.5% to 1.5% as more of these circulate in bloodstream) indicates high rate of RBC formation Copyright 2010, John Wiley & Sons, Inc. RBC Synthesis: Erythropoiesis Production and destruction: normally balanced Stimulus for erythropoiesis is low O2 delivery (hypoxia) in blood passing to kidneys Kidneys release erythropoietin release (EPO) Stimulates erythropoiesis in red marrow increased O2 delivery in blood (negative feedback mechanism) Copyright 2010, John Wiley & Sons, Inc. RBC Synthesis: Erythropoiesis Signs of lower-than-normal RBC count changes in skin, mucous membranes, and finger nail beds Cyanosis: bluish color Anemia: pale color Copyright 2010, John Wiley & Sons, Inc. Regulation of Erythropoiesis Copyright 2010, John Wiley & Sons, Inc. White Blood Cells (WBCs or Leukocytes) Appear white because lack hemoglobin Normal WBC count: 5,000-10,000/µl WBC count usually increases in infection Two major classes based on presence or absence of granules (vesicles) in them] Granular: neutrophils, eosinophils, basophils Neutrophils usually make up 2/3 of all WBCs Agranular: lymphocytes, monocytes Major function: defense against Infection and inflammation Antigen-antibody (allergic) reactions Copyright 2010, John Wiley & Sons, Inc. White Blood Cell Functions Neutrophils: first responders to infection Monocytes macrophages (“big eaters”) Phagocytosis Release bacteria-destroying enzyme lysozyme Known as wandering macrophages Eosinophils Phagocytose antibody-antigen complexes Help suppress inflammation of allergic reactions Respond to parasitic infections Copyright 2010, John Wiley & Sons, Inc. White Blood Cell Functions Basophils Intensify inflammatory responses and allergic reactions Release chemicals that dilate blood vessels: histamine and serotonin; also heparin (anticoagulant) Copyright 2010, John Wiley & Sons, Inc. White Blood Cell Functions Lymphocytes Three types of lymphocytes T cells B cells Natural killer (NK) cells Play major roles in immune responses B lymphocytes respond to foreign substances called antigens and differentiate into plasma cells that produce antibodies. Antibodies attach to and inactivate the antigens. T lymphocytes directly attack microbes. Copyright 2010, John Wiley & Sons, Inc. White Blood Cell Functions Major histocompatibility (MHC) antigens Proteins protruding from plasma membrane of WBCs (and most other body cells) Called “self-identity markers” Unique for each person (except for identical twins) An incompatible tissue or organ transplant is rejected due to difference in donor and recipient MHC antigens MHC antigens are used to “type tissues” to check for compatibility and reduce risk of rejection Copyright 2010, John Wiley & Sons, Inc. WBC Life Span WBCs: 5000-10,000 WBCs/µl blood RBCs outnumber WBCs about 700:1 Life span: typically a few hours to days Abnormal WBC counts Leukocytosis: high WBC count in response to infection, exercise, surgery Leukopenia: low WBC count Differential WBC count: measures % of WBCs made up of each of the 5 types Copyright 2010, John Wiley & Sons, Inc. Platelets Myeloid stem cells megakaryocytes 2000–3000 fragments = platelets Normal count: 150,000-400,000/µl blood Functions Plug damaged blood vessels Promote blood clotting Life span 5–9 days Copyright 2010, John Wiley & Sons, Inc. Hemostasis: “Blood Standing Still” Sequence of events to avoid hemorrhage 1. Vascular spasm Response to damage Quick reduction of blood loss 2. Platelet plug formation Platelets become sticky when contact damaged vessel wall 3. Blood clotting (coagulation) Series of chemical reactions involving clotting factors Copyright 2010, John Wiley & Sons, Inc. Blood Clotting (Coagulation) Extrinsic pathway Intrinsic Pathway Tissue factor(TF) from damaged cells 1 2 3 Materials “intrinsic” to blood 1 2 3 Common pathway: 3 major steps 1. Prothrombinase 2. Prothrombin thrombin 3. Fibrinogen fibrin clot Ca++ plays important role in many steps Copyright 2010, John Wiley & Sons, Inc. Clot Retraction and Vessel Repair Clot plugs ruptured area Gradually contracts (retraction) Pulls sides of wound together Repair Fibroblasts replace connective tissue Epithelial cells repair lining Copyright 2010, John Wiley & Sons, Inc. Hemostatic Control Mechanisms Fibrinolysis: breakdown of clots by plasmin Inappropriate (unneeded) clots Inactivated plasminogen Activated (by tPA) plasmin Clots can be triggered by roughness on vessel wall = thrombosis Loose (on-the-move) clot = embolism Anticoagulants: decrease clot formation Heparin Warfarin (Coumadin) Copyright 2010, John Wiley & Sons, Inc. (a) Extrinsic pathway Stages of Clotting Tissue trauma (b) Intrinsic pathway Blood trauma Damaged endothelial cells expose collagen fibers Tissue factor (TF) Damaged platelets Activated XII Activated platelets Ca2+ Ca2+ + Platelet phospholipids Activated X Activated X V 1 Ca2+ Ca2+ V + PROTHROMBINASE (c) Common pathway Ca2+ Prothrombin (II) THROMBIN Ca2+ 2 XIII Fibrinogen (I) Activated XIII Loose fibrin threads STRENGTHENED FIBRIN THREADS 3 Copyright 2010, John Wiley & Sons, Inc. Blood Groups and Blood Types RBCs have antigens (agglutinogens) on their surfaces Each blood group consists of two or more different blood types There are > 24 blood groups Two examples: ABO group has types A, B, AB, O Rh group has type Rh positive (Rh+), Rh negative (Rh–) Blood types in each person are determined by genetics Copyright 2010, John Wiley & Sons, Inc. ABO Group Two types of antigens on RBCs: A or B Type A has only A antigen Type B has only B antigen Type AB has both A and B antigens Type O has neither A nor B antigen Most common types in US: type O and A Typically blood has antibodies in plasma These can react with antigens Two types: anti-A antibody or anti-B antibody Blood lacks antibodies against own antigens Type A blood has anti-B antibodies (not anti-A) Type AB blood has neither anti-A nor anti-B antibodies Copyright 2010, John Wiley & Sons, Inc. ABO Group Copyright 2010, John Wiley & Sons, Inc. Rh Blood Group Name Rh: antigen found in rhesus monkey Rh blood types If RBCs have Rh antigen: Rh+ If RBCs lack Rh antigen: Rh– Rh+ blood type in 85-100% of U.S. population Normally neither Rh+ nor Rh– has anti-Rh antibodies Antibodies develop in Rh- persons after first exposure to Rh+ blood in transfusion (or pregnancy hemolytic disease of newborn) Copyright 2010, John Wiley & Sons, Inc. Transfusions If mismatched blood (“wrong blood type”) given, antibodies bind to antigens on RBCs hemolyze RBCs Type 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 Copyright 2010, John Wiley & Sons, Inc. End of Chapter 14 Copyright 2010 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permission Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publishers assumes no responsibility for errors, omissions, or damages caused by the use of theses programs or from the use of the information herein. Copyright 2010, John Wiley & Sons, Inc.