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Human Anatomy, Second Edition

McKinley & O'Loughlin

Chapter 21 Lecture Outline: Blood

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Cardiovascular System Blood, heart and blood vessels Lymphatic system is closely

related Circulatory system =

cardiovascular system and lymphatic system

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General Composition and Functions of Blood A connective tissue: cells and a liquid ground

substance and dissolved protein fibers (plasma).

About four times more viscous (thicker) than water.

Temperature is about 1°C higher than measured body temperature (38 degrees).

8% of body weight = 5 liters Can be broken down into its liquid and cellular

components by a machine called a centrifuge.

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Components of Blood Plasma

straw-colored liquid that rises to the top about 55% of blood

Buffy coat middle layer thin, slightly gray-white layer composed of

leukocytes and platelets less than 1% of a blood sample

Erythrocytes (or red blood cells) lowest layer about 44% of a blood sample

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Components of Blood Erythrocytes and the components of

the buffy coat are called the formed elements. WBCs are cells RBCs, no nuclei or other organelles, can’t

divide Platelets, merely fragments broken off

from a larger cell, can’t divide Formed elements plus liquid plasma

compose whole blood.

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Functions of Blood –Transportation Transports numerous elements and compounds

throughout the body: gases, nutrients, heat, wastes, hormones erythrocytes carry most of the oxygen

and some of the carbon dioxide blood plasma

nutrients absorbed from the GI tract hormones waste products from the cells to organs such

as the kidneys, where these waste products are removed

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Functions of Blood – Regulation: Body Temperature

Plasma absorbs and distributes heat throughout the body

For cooling, the blood vessels in the dermis dilate and dissipate the excess heat through the integument

To conserve heat, the dermal blood vessels constrict, and the warm blood is shunted to deeper blood vessels in the body

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Functions of Blood – Regulation: pH Levels pH is a measure of how alkaline or acidic a fluid is. Neutral pH is exactly 7 (0-14). Blood plasma contains compounds and ions that may

be distributed to the fluid among tissues (interstitial fluid) to help maintain normal tissue pH.

Blood plasma pH is continuously regulated at a value of 7.4 (7.35-7.45) for normal cellular functioning.

If pH falls to 7.0, then acidosis, and CNS depression, coma, and death possibly

If pH rises to 7.8, then alkalosis, and hyperexcited nervous system and convulsions

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Functions of Blood – Regulation: Fluid Levels Blood contains compounds (such as salts

and some proteins) to prevent excess fluid loss in the plasma.

Constant exchange of fluid between the blood plasma and the interstitial fluid.

Water content of cells regulated through blood osmotic pressure, esp. dissolved ions and proteins

If too much fluid is absorbed in the blood, high blood pressure results.

If too much fluid escapes the bloodstream and enters the tissues, blood pressure drops to unhealthy low levels, and the tissues swell with excess fluid (edema).

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Functions of Blood – Protection Leukocytes (white blood cells) help guard

against infection by mounting an immune response if a pathogen or an antigen is found.

Plasma transports antibodies, which are molecules that can immobilize antigens until a leukocyte can completely kill or remove the antigen.

Platelets and blood proteins protect the body against blood loss by forming blood clots on damaged vessels.

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Blood Plasma Complex mixture of water,

proteins, and other solutes. Serum = plasma - clotting

proteins Water makes up about 92% of

plasma’s total volume. water facilitates the transport of

materials in the plasma

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Plasma Proteins The next most abundant materials in

plasma are the plasma proteins. Make up about 7% of the plasma. The plasma proteins include:

albumins globulins fibrinogen regulatory proteins

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Plasma Proteins – Albumins Smallest and most abundant of the

plasma proteins. make up approximately 58% of total

plasma proteins Regulate water movement between the

blood and interstitial fluid. Albumins act as transport proteins that

carry ions, hormones, and some lipids in the blood.

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Plasma Proteins – Globulins Second largest group, about 37% of all

plasma proteins. Smaller alpha-globulins and the larger beta-

globulins primarily bind, support, and protect certain water-insoluble or hydrophobic molecules, hormones, and ions.

Gamma-globulins or immunoglobulins or antibodies. Produced by some of our defense cells to

protect the body against pathogens that may cause disease.

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Plasma Proteins – Fibrinogen About 4% of all plasma proteins. Responsible for blood clot formation. Following trauma to the walls of blood

vessels, the soluble fibrinogen is converted into long, insoluble strands of fibrin, the essence of a blood clot.

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Plasma Proteins – Regulatory Proteins <1% Include enzymes to accelerate

chemical reactions in the blood and hormones being transported throughout the body to target cells.

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Differences Between Plasma and Interstitial Fluid Plasma is an extracellular fluid (ECF), a body

fluid outside cells Plasma is similar to interstitial fluid

(fluid between cells) both have similar concentrations of

nutrients, waste products, and electrolytes The concentrations of oxygen and

carbon dioxide are different to ensure the movement of the gases in the right directions

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Formed Elements in the Blood Erythrocytes

make up more than 99% of formed elements primary function is to transport respiratory gases in

the blood Leukocytes

make up less than .01% of formed elements contribute to defending the body against pathogens

Platelets make up less than 1% of formed elements and help with blood clotting

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Hematocrit Percentage of the volume of formed elements (or

erythrocytes, clinically) in the blood. Values vary slightly and are dependent on age and sex. Adult males: 42% - 56% ; Adult females: 38% - 46%. Childrens’ hematocrit ranges also vary and differ from adult

values. Uses:

Diagnosis of anemia, polycythemia (greater than 65), and abnormal hydration

Normally higher in athletes Altitude can affect the hematocrit.

body compensates by making more erythrocytes more erythrocytes in the blood can carry more oxygen to

the tissues

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Blood Doping RBC donation to yourself Increases oxygen carrying capacity of

blood for competition Results in increased performance in

endurance events Danger: increased viscosity of blood

increases the workload for the heart and may lead to heart failure

Banned by athletic governing bodies

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Erythrocytes Transport O2 and CO2 to and from the tissues and the lungs.

About 5 million/cubic mm of blood (1/3 or all cells!) and 99.9% of formed elements.

Mature erythrocytes lack nuclei which enables them to carry

respiratory gases more efficiently.

7.5 microns in diameter - about the width of the smallest

capillaries. Rouleau formation in capillaries.

Biconcave shape

Increases surface area for gas exchange

Increases flexibility which helps them squeeze through

small capillaries No nucleus, mitochondria, or ribosomes (more room to carry

oxygen and without mitochondria, they do not use up the oxygen)

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Hemoglobin in Erythrocytes About 280 million molecules of a red-

pigmented protein called hemoglobin/RBC.

Transports almost all of the oxygen and some carbon dioxide, and is responsible for the characteristic bright red color of arterial blood.

Hemoglobin that contains no oxygen has a deep red color that is perceived as blue because the blood within these veins is observed through the layers of the skin (with collagen) and the subcutaneous tissue.

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Hemoglobin (Hb) in Erythrocytes Each Hb molecule has four protein building blocks, called

globins: 2 alpha and 2 beta chains. All globin chains contain a nonprotein (or heme) group

with an iron ion (Fe++) in its center. Each Hb molecule has four iron ions and each is capable

of binding a molecule of oxygen, i.e., 4 O2 /Hb Over 99% of the oxygen is carried by the

heme. Oxygen binding is fairly weak to ensure rapid attachment

in the lungs and detachment in the tissues. The globin carries 23% of the carbon dioxide.

Most of the carbon dioxide is carried in the bicarbonate ion.

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Erythrocyte Life Cycle About 120 days - plasma

membrane wears away Fixed macrophages in spleen and

liver remove. Also hemolysis. Components recycled.

Need about 2-3 million new mature RBC/sec to balance destruction

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Anemia: low Hct or low Hb Aplastic anemia: bone marrow Congenital hemolytic anemia: genetic Erthroblastic anemia: immature RBCs Familial microcytic anemia: genetic defect of

iron Hemorrhagic anemia: blood loss Macrocytic anemia: lack of B12 and folic acid

Pernicious anemia: lack of intrinsic factor leads to lack of B12 absorption

Sickle-cell disease: recessive genetic disease, cells sickle when oxygen low. Malaria protection from one copy of gene.

Erythrocyte Volume Disorders

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Polycythemia - Hematocrit >65 Compensatory polycythemia: chronic

hypoxia (smoker’s) Relative polycythemia: decrease in blood

plasma (dehydration-temporary) Erythrocytosis: increase in EPO Polycythemia vera: increase in blood

volume and RBCs due to loss of RBC growth regulation in red bone marrow

Erythrocyte Volume Disorders

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Blood Types Surface antigens on RBCs are genetically

determined At least 14 blood group systems and more than

100 antigens Uses

Transfusions Paternity tests Crime detection

2 major blood group classifications ABO blood grouping Rh blood grouping

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Antibodies An antibody interacts with a specific

antigen. The ABO blood group has both anti-A

and anti-B antibodies that react with the surface antigen A and the surface antigen B, respectively.

The antibodies in your blood plasma do not recognize the surface antigens on your erythrocytes.

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Transfusions Type O is the universal donor Type AB is universal recipient Whole blood seldom used. Usually

divided into three components. Erythrocytes Clotting proteins Platelets

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Anti-Rh (D) antibodies only made if Rh- person is sensitized by previous exposure to Rh+ RBCs: transfusions and pregnancy

Rh- mother who is sensitized carrying Rh+ baby could hemolyze the baby’s blood

Rho-Gam is an anti-Rh gamma globulin given to mother that inactivates Rh+ fetal blood cells in mother’s blood before she becomes sensitized and produced antibodies

Hemolytic Disease of the Newborn (Erthroblastosis fetalis)

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Red bone marrow - need to match Hipbones used: heparin added, passed

through screens, T-cells removed, injected, reseed bone marrow

Uses: Aplastic anemia Some leukemias Severe combined immunodeficiency

disease

Bone Marrow Transplant

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Leukocytes Help initiate an immune response and defend the

body against invading pathogens. “Cells.” About 1.5 to 3 times larger than RBCs and no

hemoglobin. Fight infections in the loose connective tissues

outside the capillaries Blood: 5000-10,000/mm3 but most are outside

the blood! Leukopenia = lack possibly from viral or bacterial

infection, some leukemias, or bone marrow toxins Leukocytosis = increased number may indicate

dehydration, allergy, or infection

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Leukocyte Characteristics Do not circulate for long. They move

into abnormal tissue areas. Amoeboid movement Diapedesis = squeeze through blood

vessel walls to go into tissues Positive chemotaxis Some phagocytic

Neutrophils Eosinophils Monocytes -> macrophages

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Leukocytes The five types are granulocytes or

agranulocytes — based upon the presence or absence of visible organelles termed specific granules. Granules are actually lysosomes

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Wright’s Stain Helps distinguish WBCs

Eosin is an acid stain Methylene blue is a basic stain

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Granulocytes Neutrophils (polymorphonuclear leukocytes)

60–70% of the total number of leukocytes 2-6 lobes Light colored granules with lilac cytoplasm d = 10-12 microns Increase during bacterial infections - lysozyme helps destroy

cell walls Eosinophils have reddish, or pink-orange granules in their

cytoplasm. about 2–4% of the total number of leukocytes d = 10-12 microns nucleus usually has two lobes, which are connected by a thin

strand Increase to phagocytize antigen-antibody complexes and

during parasitic worm infections

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Granulocytes Basophils are

1.5 times larger than erythrocytes about 0.5–1% of the total number of leukocytes d = 8-10 microns have a bilobed nucleus (obscured by the

granules) and abundant blue-violet granules in the cytoplasm

Contain histamine which increases the diameter of blood vessels and other allergic symptoms.

Contains heparin, a natural anticoagulant, that inhibits blood clotting.

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Agranulocytes Agranulocytes have such small granules in

their cytoplasm that they are frequently overlooked.

Agranulocytes include both lymphocytes and

monocytes.

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Lymphocytes Most are in the lymphatic tissues Small ones only have only a thin

rim of blue-gray cytoplasm around the nucleus

When activated, they grow larger and have proportionally more cytoplasm

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Types of Lymphocytes T-lymphocytes (T-cells)

manage and direct an immune response some directly attack foreign cells and virus-

infected cells B-lymphocytes (B-cells)

stimulated to become plasma cells and produce antibodies

Natural killer cells (NK cells) attack abnormal and infected tissue cells “immunological surveillance” nonspecific

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Monocytes Up to three times the diameter of an RBC. About 3–8% of all leukocytes. Nucleus is kidney-shaped or U-shaped. After about 3 days in the circulation,

monocytes move into tissues and become macrophages that phagocytize bacteria, cell fragments, dead cells, and debris.

Nonspecific

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Mnemonic Disease Never let monkeys eat

bananas

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Lifespan Varies: 12 hrs. for neutrophils to

years for lymphocytes During an infection, some may live

for only a few hours

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Characterized by abnormal development and proliferation of WBCs in the bone marrow and circulating blood

Acute leukemia: rapid progression and death in a few months following onset of symptoms

Severe anemia, hemorrhages, and recurrent infection Occurs usually in children and young adults

Chronic leukemia: progresses more slowly with survival exceeding one year following onset of symptoms

Anemia and tendency to bleed Occurs usually in middle-aged and older individuals

Good chance of cure now in childhood leukemias

Leukemia

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Platelets (Thrombocytes) Fragments (2 microns) continually shed

by megakaryocytes in the red bone marrow which then enter circulation.

120,000-about 300,000/mm3 of blood Severe trauma to a blood vessel causes the

blood to coagulate, or clot. Components in the plasma produce a web of

fibrin that traps erythrocytes and platelets in the web (platelet plug) to halt blood flow.

Lifespan: about 8-10 days

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Hemopoiesis: Production of Formed Elements Hemocytoblast (blood stem cell) Myeloid stem cells

Erythropoiesis Thrombopoiesis Leukopoiesis

Granulocytes Monocytes

Lymphoid stem cells lymphocytes

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Hemopoiesis: Production of Formed Elements Hormones and growth factors

influence the maturation and division of the blood stem cells

Called colony-stimulating factors (CSFs)

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Erythropoiesis Erythrocyte production is about three million per

second. Testosterone stimulates, but estrogen inhibits Erythropoietin released by the kidney in response to hypoxia

(low tissue oxygen levels) increases mitotic rate and accelerates maturation.

Reticulocyte count is a measure of the rate of erythropoiesis (about 1% is normal)

Low “retic” count in anemia indicates an inability for red bone marrow response

High “retic” count in anemia indicates a good red bone marrow response

Hemopoietic growth factors: recombinant available Increases RBC in end-stage kidney disease

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Thrombopoiesis A committed cell, the megakaryoblast,

produces a megakaryocyte. The megakaryocyte produces

thousands of platelets.

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Leukopoiesis Three different maturation processes:

Granulocyte maturation Monocyte maturation Lymphocyte maturation