Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Chapter 17 Blood

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Objectives:  Composition and functions of blood  Hemopoiesis  Hemostasis  Disorders of blood  Transfusion  ABO and Rh blood groups  Blood replacement  Diagnostic blood test.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Overview of Blood Circulation  Blood (a transport vehicle) exits the heart via:  Arteries that branch repeatedly into capillaries  Transported oxygen (O 2 ) and nutrients diffuse:  Across capillary walls  Enter tissues  Carbon dioxide (CO 2 ) and wastes move:  From tissues  Enter into the blood

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Overview of Blood Circulation  Oxygen-deficient blood:  leaves the capillaries  flows in veins  enter the heart  flows to the lungs  releases CO 2  picks up O 2  Oxygen-rich blood:  returns to the heart thru  (name the vessels)

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Composition of Blood  Blood is the body’s only fluid tissue  Composed of:  liquid plasma  formed elements  Formed elements include:  Erythrocytes, or red blood cells (RBCs)  Leukocytes, or white blood cells (WBCs)  Platelets  Hematocrit:  The percentage of RBCs out of the total blood volume

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Components of Whole Blood Figure 17.1

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Physical Characteristics and Volume  Blood:  Sticky, opaque fluid with a metallic taste  Color varies from scarlet red to dark red  pH of blood is 7.35–7.45  Temperature is 38  C  Approximately 8% of body weight  Average volume:  5–6 L for males  4–5 L for females

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Functions of Blood  Blood functions deal with:  Substance distribution  Substance level regulation  Body protection

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Functions of Blood: Distribution  In distribution blood transports:  Oxygen and nutrients (from lungs & digestive tract to cells)  Metabolic wastes (from cells to lungs and kidneys)  Hormones (from endocrine glands to target organs)

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Functions of Blood: Regulation  In regulation, blood maintains:  Body temperature (heat absorption & distributing)  pH (thru buffer systems)  Adequate fluid in the circulatory system (volume)

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Functions of Blood: Protection  In protection, blood:  Prevents its own loss (vessel damage):  By initiating clot formation thru plasma proteins & platelets  Defends body against foreign invaders thru:  Synthesis and utilization of antibodies  Activation of specific proteins & WBCs

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Blood Plasma Composition  About 90% water  Over 100 solutes, including proteins, which are:  The most abundant solutes in blood  Most made by the liver  Albumin:  60% of plasma proteins  Carrier to certain molecules  Blood buffer  Major osmolite ( plasma osmotic pressure contributor)

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Blood Plasma Composition(cont’d)  Globulins:  36% of plasma proteins  Transport proteins (Alpha & beta)  Synthesized by liver (Alpha & beta)  Antibodies (gamma) released by plasma cells  Fibrinogen (clotting protein, soluble)  4% of plasma proteins  Clotting protein (fibrin, insoluble)  Synthesied by the liver

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Blood Plasma Composition (cont’d)  Organic nutrients (digestion end products) :  Glucose & other simple carbohydrates, amino acids, FFA, glycerol, TG, vitamins  Electrolytes  Sodium, potassium, calcium, chloride, bicarbonate  Respiratory gases:  oxygen and carbon dioxide

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Formed Elements  Include:  Erythrocytes (RBCs):  Anucleated disc sacs of Hb  Leukocytes (WBCs) :  The only complete cells (explain?)  Platelets:  Cell fragments  Most survive for only a short time  Most do not divide but renewed by bone marrow cells

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Erythrocytes (RBCs)  Biconcave, anucleate, with no organelles  Filled with hemoglobin (Hb):  A gas transport protein  Contain plasma membrane proteins (spectrin) that:  Give erythrocytes their flexibility  Allow them to change shape as necessary

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Erythrocytes (RBCs) Figure 17.3

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Components of Whole Blood Figure 17.2

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Erythrocytes (RBCs)  RBCs structural characteristics contribute to their gas transport function:  Biconcave shape:  Provides a huge surface area relative to volume  Are more than 97% hemoglobin  Generate ATP anaerobically:  They don’t consume transported oxygen

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hemoglobin (Hb)  Hb is composed of:  The protein globin  The red heme pigment  Globin:  Made up of 4 polypeptide chains (2 α and 2 β)  Each chain is bound to a heme group  Heme:  Each heme group bears a central atom of iron  Each iron atom can bind to one oxygen molecule

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Forms of Hemoglobin (Hb)  Oxyhemoglobin:  Hb bound to oxygen  Loading of Oxygen takes place in the lungs  Deoxyhemoglobin:  Hb after oxygen diffuses into tissues (reduced Hb)  Carbaminohemoglobin:  Hb bound to carbon dioxide (20%)  CO 2 is bound to the globin’s amino acids (not to heme)  Loading of carbon dioxide takes place in the tissues

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Erythrocyte Function  Respiratory gas transport:  Hemoglobin binds oxygen reversibly  Most oxygen in the blood is bound to Hb  Class assignment:  How many oxygen molecules each Hb molecule can transport  Where are the oxygen molecules bound?  Where are the oxygen molecules:  Picked up  Delivered

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Production of Blood Cells  Hematopoiesis:  Refers to blood cell formation  Occurs in the red bone marrow of the:  Axial skeleton and girdles  Epiphyses of the humerus and femur  Hemocytoblasts:  Stem cells that give rise to all formed elements

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Production of Erythrocytes: Erythropoiesis  A hemocytoblast is transformed into a proerythroblast  Proerythroblasts develop into early erythroblasts  Developmental pathway consists of three phases:  1 – Ribosome synthesis phase: in early erythroblasts  2 – Hb accumulation phase: in late erythroblasts & normoblasts  3 – Ejection of most organelles & the nucleus from normoblasts and the formation of reticulocytes  Reticulocytes then become mature erythrocytes (disintegration of ribosomes)

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Production of Erythrocytes: Erythropoiesis Figure 17.5

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Regulation of Erythropoiesis  RBC number remains constant  This reflects a balance between their production & destruction  Imbalance of RBC production:  Too few RBCs leads to tissue hypoxia  Too many RBCs causes incresed blood viscosity  How is erythropoiesis controlled?

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hormonal Control of Erythropoiesis  The kidneys release erythropoietin (EPO) hormone  EPO release is triggered by:  Hypoxia due to decreased RBCs  Decreased Hb amount  Decreased oxygen availability  Increased tissue demand for oxygen  Enhancement of erythropoiesis results in:  Increased RBC count in circulating blood  Increased oxygen carrying ability of the blood

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Homeostasis: Normal blood oxygen levels Increases O 2 -carrying ability of blood Erythropoietin stimulates red bone marrow Reduces O 2 levels in blood Kidney (and liver to a smaller extent) releases erythropoietin Enhanced erythropoiesis increases RBC count Stimulus: Hypoxia due to decreased RBC count, decreased amount of hemoglobin, or decreased availability of O 2 Start Imbalance Erythropoietin Mechanism Figure 17.6

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings  Erythropoiesis requires:  Usual nutrients:  Proteins  Lipids  Carbohydrates  Vitamin B 12, & folic acid (for RBCs DNA synthesis)  Dietary iron  Free iron ions (Fe ++ & Fe +++ ) are toxic Dietary Requirements of Erythropoiesis

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings  The body stores of iron:  65% in Hb  Remainder in:  Liver  Spleen  Bone marrow (least)  Intracellular iron is stored in protein-iron complexes:  Ferritin  Hemosiderin  Circulating iron is loosely bound to:  A transport protein called transferrin Body Stores of Iron

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Fate and Destruction of Erythrocytes  The life span of an erythrocyte is 100–120 days  Old RBCs become rigid and fragile  Their Hb begins to degenerate  Macrophages engulf & destroy dying RBCs  Heme and globin are separated  Heme iron is salvaged as cellular protein-bound ferritin or hemosiderin for reuse  Heme remainder is degraded to the yellow pigment bilirubin  Bilirubin is transported in blood to the liver

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Fate and Destruction of Erythrocytes  Liver cells pick up bilirubin & secrete it (in bile) into the intestine  In the intestines bilirubin is metabolized into another degraded pigment (urobilinogen)  Most urobilinogen leaves the body as a brown pigment (stercobilin) in feces (fecal color)  The heme globin is metabolized into amino acids  Amino acids are released into the circulation

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hemoglobin Amino acids Globin Raw materials are made available in blood for erythrocyte synthesis. Iron is bound to transferrin and released to blood from liver as needed for erythropoiesis Food nutrients, including amino acids, Fe, B 12, and folic acid are absorbed from intestine and enter blood Heme Circulation Iron stored as ferritin, hemosiderin Bilirubin Bilirubin is picked up from blood by liver, secreted into intestine in bile, metabolized to stercobilin by bacteria and excreted in feces Erythropoietin levels rise in blood. Erythropoietin and necessary raw materials in blood promote erythropoiesis in red bone marrow. New erythrocytes enter bloodstream; function about 120 days. Low O 2 levels in blood stimulate kidneys to produce erythropoietin. Aged and damaged red blood cells are engulfed by macrophages of liver, spleen, and bone marrow; the hemoglobin is broken down Figure 17.7

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings  Anemia:  Abnormal low oxygen-carrying capacity of blood  Types & Causes: 1-Insufficient number of RBCs:  Hemorrhagic anemia:  Acute/chronic loss of blood  Hemolytic anemia:  Prematurely ruptured RBCs  Aplastic anemia:  Red bone marrow destruction/ inhibition Erythrocyte Disorders: Anemia

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings  Causes and Types: 2- Low Hemoglobin Content  Iron-deficiency anemia (microcytic) :  A secondary result of hemorrhagic anemia  Inadequate intake of iron-containing foods  Impaired iron absorption  Pernicious anemia (macrocytic) :  Deficiency of vitamin B 12 (developing RBCs grow but don’t divide)  Lack of intrinsic factor by gastric parietal cells  Intrinsic factor is required for the intestinal absorption of vit B 12 Erythrocyte Disorders: Anemia Cont’d

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Erythrocyte Disorders: Anemia (Cont’d)  3- Abnormal Hemoglobin  Thalassemias:  Absent/faulty globin chain in Hb  Sickle-cell anemia:  A defective gene coding for abnormal Hb called hemoglobin S (HbS)  HbS has a single amino acid substitution in the beta chain  This defect causes RBCs to become sickle-shaped in low oxygen situations

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Erythrocyte Disorders: Polycythemia  Polycythemia:  Excess RBCs that increase blood viscosity  Blood doping:  Induced polycythemia by athletes  Blood is withdrawn and re-infused later before the event