Chapter 17 Blood Mosby items and derived items

Composition of Blood Introduction (Figure 17 -1) Ø Blood—made up of plasma and formed elements Ø Blood—complex transport medium that performs vital pickup and delivery services for the body Ø Blood—keystone of body’s heat-regulating mechanism Blood volume Ø Young adult male has approximately 5 liters of blood Ø Blood volume varies according to age, body type, sex, and method of measurement Mosby items and derived items © 2007, 2003 by Mosby, Inc. 2

Formed Elements of Blood Red blood cells (erythrocytes) Ø Description of mature red blood cells (RBCs) (Figure 17 -4) • Have no nucleus and are shaped like tiny, biconcave disks • Do not contain ribosomes, mitochondria, and other organelles typical of most body cells • Primary component is hemoglobin • Most numerous of the formed elements Ø Function of RBCs • RBCs’ critical role in the transport of oxygen and carbon dioxide depends on hemoglobin • Carbonic anhydrase—enzyme in RBCs that catalyzes a reaction that joins carbon dioxide and water to form carbonic acid • Carbonic acid—dissociates and generates bicarbonate ions, which diffuse out of the RBC and serve to transport carbon dioxide in the blood plasma Mosby items and derived items © 2007, 2003 by Mosby, Inc. 3

Formed Elements of Blood Red blood cells (erythrocytes) (cont. ) Ø Hemoglobin (Figure 17 -5) • Within each RBC are approximately 200 to 300 million molecules of hemoglobin • Hemoglobin is made up of four globin chains, each attached to a heme molecule • Hemoglobin is able to unite with four oxygen molecules to form oxyhemoglobin to allow RBCs to transport oxygen where it is needed • A male has a greater amount of hemoglobin than a female • Anemia—a decrease in number or volume of functional RBCs in a given unit of whole blood Mosby items and derived items © 2007, 2003 by Mosby, Inc. 4

Formed Elements of Blood Red blood cells (erythrocytes) (cont. ) Ø Formation of red blood cells (review Figures 17 -6 and 17 -7) • Erythropoiesis—entire process of RBC formation • RBC formation begins in the red bone marrow with hemopoietic stem cells that go through several stages of development to become erythrocytes; entire maturation process requires approximately 4 days • RBCs are created and destroyed at a rate of approximately 100 million per minute in an adult; homeostatic mechanisms operate to balance number of cells formed against number of cells destroyed Ø Destruction of RBCs (Figure 17 -8) • Life span of a circulating RBC averages 105 to 120 days • Macrophage cells phagocytose the aged, abnormal, or fragmented RBCs • Hemoglobin is broken down and amino acids, iron, and bilirubin are released Mosby items and derived items © 2007, 2003 by Mosby, Inc. 5

Formed Elements of Blood White blood cells (leukocytes, WBCs) (review Table 17 -1) Ø Granulocytes • Neutrophils (review Figure 17 -9)—make up approximately 65% of total WBC count in a normal blood sample; highly mobile and very active phagocytic cells; capable of diapedesis; cytoplasmic granules contain lysosomes • Eosinophils (review Figure 17 -10)—account for 2% to 5% of circulating WBCs; numerous in lining of respiratory and digestive tracts; weak phagocytes; capable of ingesting inflammatory chemicals and proteins associated with antigen-antibody reaction complexes; provide protection against infections caused by parasitic worms and allergic reactions • Basophils (review Figure 17 -11)—account for only 0. 5% to 1% of circulating WBCs; motile and capable of diapedesis; cytoplasmic granules contain histamine and heparin Mosby items and derived items © 2007, 2003 by Mosby, Inc. 6

Formed Elements of Blood White blood cells (cont. ) Ø Agranulocytes (Figures 17 -12 and 17 -13) • Lymphocytes—smallest of the WBCs; second most numerous type of WBC; account for approximately 25% of circulating WBCs; T lymphocytes and B lymphocytes have an important role in immunity—T lymphocytes directly attack an infected or cancerous cell, and B lymphocytes produce antibodies against specific antigens • Monocytes—largest type of leukocyte; mobile and highly phagocytic cells WBC numbers—a cubic millimeter of normal blood usually contains 5, 000 to 9, 000 leukocytes, with different percentages for each type; WBC numbers have clinical significance because they change with certain abnormal conditions Ø Formation of WBCs (review Figure 17 -6) Ø • Granular and agranular leukocytes mature from the undifferentiated hemopoietic stem cell • Neutrophils, eosinophils, basophils, and a few lymphocytes and monocytes originate in red bone marrow; most lymphocytes and monocytes develop from hemopoietic stem cells in lymphatic tissue Mosby items and derived items © 2007, 2003 by Mosby, Inc. 7

Formed Elements of Blood Platelets (review Figure 17 -12) Ø Structure • In circulating blood, platelets are small, pale bodies that appear as irregular spindles or oval disks • Three important properties are agglutination, adhesiveness, and aggregation • Platelet counts in adults average 250, 000 per mm 3 of blood; normal range is 150, 000 to 400, 000 per mm 3 Ø Functions of platelets • Important role in hemostasis and blood coagulation • Hemostasis—refers to stoppage of blood flow; however, if injury is extensive, the blood-clotting mechanism is activated to assist Mosby items and derived items © 2007, 2003 by Mosby, Inc. 8

Formed Elements of Blood Platelets (cont. ) Ø Platelet plug formation • 1 to 5 seconds after injury to vessel wall, platelets adhere to damaged endothelial lining and to each other, forming a platelet plug • Temporary platelet plug is an important step in hemostasis • Normal platelets (positive charge) adhere to damaged capillary wall and underlying collagen fibers, which both have a negative charge • “Sticky platelets” form physical plug and secrete several chemicals involved in the coagulation process Ø Formation and life span of platelets (7 to 10 days)—formed in red bone marrow, lungs, and spleen by fragmentation of megakaryocytes Mosby items and derived items © 2007, 2003 by Mosby, Inc. 9

Blood Types (Blood Groups) The ABO system (Figures 17 -15 to 17 -17) Ø Every person’s blood belongs to one of four ABO blood groups Ø Named according to antigens present on RBC membranes • Type A—antigen A on RBC • Type B—antigen B on RBC • Type AB—both antigen A and antigen B on RBC; known as universal recipient • Type O—neither antigen A nor antigen B on RBC; known as universal donor Mosby items and derived items © 2007, 2003 by Mosby, Inc. 10

Blood Types (Blood Groups) The Rh system (Figure 17 -18) Ø Rh-positive blood—Rh antigen is present on the RBCs Ø Rh-negative—RBCs have no Rh antigen present Ø Anti-Rh antibodies are not normally present in blood; anti-Rh antibodies can appear in Rh-negative blood if it has come in contact with Rh-positive RBCs Mosby items and derived items © 2007, 2003 by Mosby, Inc. 11

Blood Plasma Plasma—liquid part of blood; clear, straw-colored fluid; made up of 90% water and 10% solutes (Figure 17 -19) Solutes— 6% to 8% of plasma solutes are proteins, consisting of three main compounds: Ø Albumins—helps maintain osmotic balance of the blood Ø Globulins—essential component of the immunity mechanism Ø Fibrinogen—key role in blood clotting Plasma proteins have an essential role in maintaining normal blood circulation Mosby items and derived items © 2007, 2003 by Mosby, Inc. 12

Blood Clotting (Coagulation) Mechanism of blood clotting—goal of coagulation is to stop bleeding and prevent loss of vital body fluid in a swift and sure method; the “classic theory” (Figure 17 -20) is as follows: Ø “Classic theory” of coagulation advanced in 1905 • Identified four components critical to coagulation: Prothrombin Thrombin Fibrinogen Fibrin Mosby items and derived items © 2007, 2003 by Mosby, Inc. 13

Blood Clotting (Coagulation) Mechanism of blood clotting (cont. ) Ø Current explanation of coagulation involves three stages: (Figure 17 -21) • Stage I—production of thromboplastin activator by one or the other of the following: • • chemicals released from damaged tissues (extrinsic pathway) chemicals present in the blood (intrinsic pathway) Stage II—conversion of prothrombin to thrombin Stage III—conversion of fibrinogen to fibrin and production of fibrin clot Mosby items and derived items © 2007, 2003 by Mosby, Inc. 14

Blood Clotting (Coagulation) Conditions that oppose clotting Ø Clot formation in intact vessels is opposed Ø Several factors oppose clotting • Perfectly smooth surface of the normal endothelial lining of blood vessels does not allow platelets to adhere • Antithrombins—substances in the blood that oppose or inactivate thrombin; prevent thrombin from converting fibrinogen to fibrin; e. g. , heparin Mosby items and derived items © 2007, 2003 by Mosby, Inc. 15

Blood Clotting (Coagulation) Conditions that hasten clotting Ø Rough spot in the endothelium Ø Abnormally slow blood flow Clot dissolution (Figure 17 -22) Ø Fibrinolysis—physiological mechanism that dissolves fibrin Ø Fibrinolysin—enzyme in the blood that catalyzes the hydrolysis of fibrin, causing it to dissolve Ø Additional factors are presumed to aid clot dissolution; e. g. , substances that activate profibrinolysin Mosby items and derived items © 2007, 2003 by Mosby, Inc. 16

The Big Picture: Blood and the Whole Body Blood plasma transports substances, including heat, around the body, linking all body tissues together Ø Substances can be transported between almost any two points in the body Blood tissue contains formed elements—blood cells and platelets Ø RBCs assist in the transport of oxygen and carbon dioxide Ø WBCs assist in the defense mechanisms of the whole body Ø Platelets prevent loss of the fluid that constitutes the internal environment Mosby items and derived items © 2007, 2003 by Mosby, Inc. 17

The Big Picture: Blood and the Whole Body No organ or system of the body can maintain proper levels of nutrients, gases, or water without direct or indirect help from blood Ø Other systems assist the blood Blood is useless unless it continues to transport, defend, and maintain balance Mosby items and derived items © 2007, 2003 by Mosby, Inc. 18