chapter 19- blood

Copyright © 2010 Pearson Education, Inc.

Chapter 19- Blood


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


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


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


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


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


• 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


Blood Plasma proteins

• 8% of plasma weight

• Contribute to osmotic pressure

• Proteins are mostly produced by the liver

• 60% albumin

• 36% globulins

• 4% fibrinogen


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


• 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


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


• 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


• 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


• 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


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 – –


• 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


• 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


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.


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


• 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


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.


• 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


• 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


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


http://pathy.med.nagoya-u.ac.jp/atlas/img/t2/img0027.jpg

Thalassemias – absent or faulty globin chain in Hb RBCs are thin, delicate, and deficient in Hb

Anemia: Abnormal Hemoglobin


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


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


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


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


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


• 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


• 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


Agranulocytes

• Agranulocytes: lymphocytes and monocytes

• Lack visible cytoplasmic granules

• Have spherical or kidney-shaped nuclei


• 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


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


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


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


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


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)

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