Download - Chapter 19- Blood
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Chapter 19- Blood
Copyright © 2010 Pearson Education, Inc.
Functions of Blood• Substance distribution:
• Oxygen from the lungs and nutrients from the digestive tract
• Metabolic wastes from cells to the lungs and kidneys for elimination
• Hormones from endocrine glands to target organs
• Regulation:
• Appropriate body temperature by absorbing and distributing heat
• Normal pH in body tissues using buffer systems
• Adequate fluid volume in the circulatory system
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Functions of Blood• Body protection
• prevents blood loss by:• Activating plasma proteins and platelets • Initiating clot formation when a vessel is broken
• Blood prevents infection by: • Synthesizing and utilizing antibodies• Activating complement proteins• Activating WBCs to defend the body against
foreign invaders
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Physical Characteristics and Volume
• Color varies from scarlet to dark red• The pH of blood is 7.35–7.45• Temperature is 38C• Blood accounts for approximately 8% of body weight• Average volume: 5–6 L for males, and 4–5 L for
females
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Composition of Blood• What type of tissue is blood?
• It is composed of liquid plasma (matrix) and formed elements
• Formed elements include:
• Erythrocytes, or red blood cells (RBCs)
• Leukocytes, or white blood cells (WBCs)
• Platelets
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Blood Plasma
• Blood plasma contains over 100 solutes, including:• Proteins – albumin, globulins, clotting proteins,
and others• Lactic acid, urea, creatinine• Organic nutrients – glucose, carbohydrates, amino
acids• Electrolytes – sodium, potassium, calcium,
chloride, bicarbonate • Respiratory gases – oxygen and carbon dioxide
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• Accounts for 46-63% of blood volume
• 92% of plasma is water
• In many respects, plasma composition resembles that of the interstitial fluid
• The differences between plasma and interstitial fluids are:
• Concentration of dissolved oxygen and carbon dioxide
• Concentration of dissolved proteins (plasma proteins can not cross capillary walls)
Plasma
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Blood Plasma proteins
• 8% of plasma weight
• Contribute to osmotic pressure
• Proteins are mostly produced by the liver
• 60% albumin
• 36% globulins
• 4% fibrinogen
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Formed Elements
• Erythrocytes, leukocytes, and platelets make up the formed elements
• Only WBCs are complete cells• RBCs have no nuclei or organelles, and platelets
are just cell fragments• Most formed elements survive in the bloodstream for
only a few days• Most blood cells do not divide but are renewed by
cells in bone marrow
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• What is the function of erythrocytes?
• What elements in their structure support their function?
• Function – carry respiratory gases – mainly oxygen
• They contain hemoglobin and have a biconcave structure that helps with moving into small blood
vessels
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Erythrocytes (RBCs)• Biconcave discs, anucleate, essentially no organelles• Filled with hemoglobin (Hb), a protein that functions in gas transport• The biconcave disc shape
• provides a large surface to volume ratio – help with fast exchange between the cell and the plasma
• allows RBCs to stack – facilitate flow through narrow blood vessels
• Allows the RBCs to bend and flex when entering small capillaries• Structural characteristics contribute to its gas transport function
• Erythrocytes are more than 97% hemoglobin• ATP is generated anaerobically through glycolysis (they lack
mitochondria), so the erythrocytes do not consume the oxygen they transport
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• The hematocrit (also called volume of packed red cells, VPRC, or packed cell volume, PCV) is a measure of the relative percentage of blood cells (mainly erythrocytes) in a given volume of whole blood.
• Normal hematocrit for Adult Females: 37-48% (ave. 42%)
• Normal hematocrit for Adult Males: 42-52% (ave. 47%)
Hematocrit Measurement
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• RBC membranes have glycoprotein antigens on their external surfaces
• These antigens are:• Unique to the individual • Recognized as foreign if transfused into another
individual• Promoters of agglutination and are referred to as
agglutinogens • Presence or absence of these antigens is used to
classify blood groups
Human Blood Groups
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• The ABO blood groups consists of:• Two antigens (A and B) on the surface of the
RBCs • Two antibodies in the plasma (anti-A and anti-B)
• ABO blood groups may have various types of antigens and preformed antibodies
• Agglutinogens and their corresponding antibodies cannot be mixed without serious hemolytic reactions
ABO Blood Groups
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Blood Typing• When serum containing anti-A or anti-B agglutinins is added to
blood, agglutination will occur between the agglutinin and the corresponding agglutinogens
• Positive reactions indicate agglutination
Blood type being tested
RBC agglutinogens Serum Reaction
Anti-A Anti-B
AB A and B + +
B B – +
A A + –
O None – –
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• Transfusion reactions occur when mismatched blood is infused
• Donor’s cells are attacked by the recipient’s plasma agglutinins causing:
• Diminished oxygen-carrying capacity
• Clumped cells that impede blood flow
• Ruptured RBCs that release free hemoglobin into the bloodstream
• Circulating hemoglobin precipitates in the kidneys and causes renal failure
Transfusion Reactions
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• There are eight different Rh agglutinogens, three of which (C, D, and E) are common
• Presence of the Rh agglutinogens on RBCs is indicated as Rh+
• Anti-Rh antibodies are not spontaneously formed in Rh– individuals
• However, if an Rh– individual receives Rh+ blood, anti-Rh antibodies form
• A second exposure to Rh+ blood will result in a typical transfusion reaction
Rh Blood Groups
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RH factor blood grouping system• A person with Rh- blood can develop Rh antibodies in the blood plasma
if he or she receives blood from a person with Rh+ blood, whose Rh antigens can trigger the production of Rh antibodies.
• A person with Rh+ blood can receive blood from a person with Rh- blood without any problems.
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Homeostatic Imbalance: Hemolytic Disease of the Newborn• Also called erythroblastosis fetalis• Rh– mother becomes sensitized when exposure to Rh+
blood causes her body to synthesize anti-Rh antibodies
• Anti-Rh antibodies cross the placenta and destroy the RBCs of an Rh+ baby
• The baby can be treated with prebirth transfusions and exchange transfusions after birth
• RhoGAM serum containing anti-Rh can prevent the Rh– mother from becoming sensitized
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• Erythropoiesis requires:
• Proteins, lipids, and carbohydrates
• Iron
• vitamin B12, and folic acid (necessary for DNA production)
• Location of iron in the body• The body stores iron in Hb (65%), the liver, spleen, and bone
marrow
• Intracellular iron is stored in protein-iron complexes such as ferritin and hemosiderin
• Circulating iron is loosely bound to the transport protein transferrin
Dietary Requirements of Erythropoiesis
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RBC formation and turnover
• The life span of an erythrocyte is 100–120 days
• Old RBCs become rigid and fragile, and their Hb begins to degenerate
• RBC travels about 700 miles in 120 days and is being colliding in other RBCs or the vessels walls
• The damage in the RBC is detected by phagocytes that engulf the RBCs
• RBCs are replaced at a rate of approximately 3 million new blood cells entering the circulation per second.
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• Anemia – blood has abnormally low oxygen-carrying capacity
• It is a symptom rather than a disease itself
• Blood oxygen levels cannot support normal metabolism
• Signs/symptoms include fatigue, paleness, shortness of breath, and chills
• Hemorrhagic anemia – result of acute or chronic loss of blood
• Hemolytic anemia – prematurely ruptured RBCs
• Aplastic anemia – destruction or inhibition of red bone marrow
Erythrocyte Disorders
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• Iron-deficiency anemia results from:
• A secondary result of hemorrhagic anemia
• Inadequate intake of iron-containing foods
• Impaired iron absorption• Pernicious anemia results from:
• Deficiency of vitamin B12
• Lack of intrinsic factor needed for absorption of B12
• Treatment is intramuscular injection of B12
Anemia: Decreased Hemoglobin Content
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Anemia: Abnormal Hemoglobin• Sickle-cell anemia – results from a defective gene coding for an
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
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Thalassemias – absent or faulty globin chain in Hb RBCs are thin, delicate, and deficient in Hb
Anemia: Abnormal Hemoglobin
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Erythrocyte Disorders - polycythemia
• Polycythemia: excess of RBCs that increase blood viscosity
• Results from:
• Polycythemia vera — bone marrow cancer
• Secondary polycythemia — when less O2 is available (high altitude) or when EPO production increases
• Blood doping – increase RBC by infusion or by injections of erythropoietin
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Leukocytes (WBCs)
• Leukocytes, the only blood components that are complete cells:
• Are less numerous than RBCs• Make up 1% of the total blood volume• Can leave capillaries via diapedesis• Move through tissue spaces
• Leukocytosis – WBC count over 11,000 / mm3
• Normal response to bacterial or viral invasion
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Types of WBC• Five types of WBC: neutrophils, eosinophils, basophils,
monocytes, lymphocytes
• First 4 are part of the body non-specific defense and lymphocytes are part of the specific defense (will be discussed later in the course)
• WBC are divided into 2 groups on the basis of their appearance after staining:
• Granulocytes – visible stained granules
• Agranulocytes – non-visible granules
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Granulocytes• Granulocytes –
• Neutrophils – netural granules
• Eosinophils – acidic staining
• Basophils – basic staining
• Contain cytoplasmic granules that stain specifically (acidic, basic, or both) with Wright’s stain
• Are larger and usually shorter-lived than RBCs
• Have lobed nuclei
• Are all phagocytic cells
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Neutrophils• 50-70% of WBC• Segmented nuclei with 2-5 lobes
(polymorphonuclear)• Highly mobile• First to arrive to site of injury• Attack and digest bacteria that have
been marked with antibodies (Ab)• Contain peroxidases, hydrolytic
enzymes, and defensins (antibiotic-like proteins)
• Short life span (~10d); if activated live 30min or less
• Breakdown of a neutrophil releases chemicals that attract other neutrophils
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• Eosinophils account for 1–4% of WBCs
• Have bilobed nuclei connected via a broad band of nuclear material
• Have red to crimson (acidophilic) large, granules
• attack parasites and phagocyte antigen-antibody complexes
Eosinophils
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• Account for 0.5% of WBCs• Have U- or S-shaped nuclei• The staining of the granules is dark and
obscure the nucleus• Have large, purplish-black (basophilic)
granules that contain histamine• Histamine – inflammatory chemical
that acts as a vasodilator and attracts other WBCs (antihistamines counter this effect)
• In the site of injury releases granules that contain histamine (vassodilator) and heparin( prevents clotting)
Basophils
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Agranulocytes
• Agranulocytes: lymphocytes and monocytes
• Lack visible cytoplasmic granules
• Have spherical or kidney-shaped nuclei
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• Account for 25% or more of WBCs• Have large, dark-purple, circular
nuclei with a thin rim of blue cytoplasm
• Are found mostly in lymphoid tissue (some circulate in the blood)
• There are two types of lymphocytes:• T cells function in the immune
response • B cells give rise to plasma cells,
which produce antibodies
Lymphocytes
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Monocytes• Monocytes account for 4–8% of
leukocytes
• They are the largest leukocytes
• They have abundant pale-blue cytoplasm
• They have purple-staining, U- or kidney-shaped nuclei
• They leave the circulation, enter tissue, and differentiate into macrophages
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Leukopoiesis
• Production of WBCs
• Stimulated by chemical messengers from bone marrow and mature WBCs
• Interleukins (e.g., IL-1, IL-2)
• Colony-stimulating factors (CSFs) named for the WBC type they stimulate (e.g., granulocyte-CSF stimulates granulocytes)
• All leukocytes originate from hemocytoblasts
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Leukocyte Disorders
• Leukopenia
• Abnormally low WBC count—drug induced
• Leukemias
• Cancerous conditions involving WBCs
• Named according to the abnormal WBC clone involved
• Myelocytic leukemia involves myeloblasts
• Lymphocytic leukemia involves lymphocytes
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Leukemia
• Bone marrow totally occupied with cancerous leukocytes
• Immature nonfunctional WBCs in the bloodstream
• Death caused by internal hemorrhage and overwhelming infections
• Treatments include irradiation, antileukemic drugs, and stem cell transplants
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Platelets
• Small fragments of megakaryocytes
• Formation is regulated by thrombopoietin
• Blue-staining outer region, purple granules
• Granules contain serotonin, Ca2+, enzymes, ADP, and platelet-derived growth factor (PDGF)