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Human Anatomy, First Edition

McKinley & O'Loughlin

Chapter 21 Lecture Outline: Blood

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Blood Considered a connective tissue because it contains

cells, a liquid ground substance (called plasma), and dissolved protein fibers.

About four times more viscous (or thicker) than water. Temperature of blood is about 1°C higher than

measured body temperature. Can be broken down into its liquid and cellular

components by a machine called a centrifuge. blood is withdrawn from a vein and collected in a

centrifuge tube tube is placed into the centrifuge, which then spins it in a

circular motion for several minutes rotational movement separates the blood into liquid and

cellular components

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Components of Blood Erythrocytes (or red blood cells)

form the lower layer of the centrifuged blood typically make up about 44% of a blood sample

Buffy coat makes up the middle layer thin, slightly gray-white layer composed of cells

called leukocytes (or white blood cells) and cell fragments called platelets

forms less than 1% of a blood sample Plasma

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

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Components of Blood Erythrocytes and the components of the buffy

coat are called the formed elements. not “cells,” merely fragments broken off from a

larger cell Formed elements and the liquid plasma

compose whole blood.

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Functions of Blood –Transportation Transports numerous elements and compounds

throughout the body. erythrocytes carry oxygen from the lungs to body cells

and then transport carbon dioxide from the cells back to the lungs for expulsion from the body

blood plasma transports nutrients that have been absorbed from the GI

tract hormones secreted by the endocrine organs to their

target cells plasma

carries 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 of Body Temp. Regulates 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

when the body needs 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 of pH Levels pH is a measure of how alkaline or acidic a fluid is. Neutral pH is measured at exactly 7. Acidic fluids (e.g., orange juice) are between 0 and 7. Alkaline fluids (e.g., milk) are between 7 and 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 the pH level required for normal cellular functioning.

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Functions of Blood – Maintenance of Fluid Levels Maintains normal fluid levels in the

cardiovascular system. Prevents fluid loss. Constant exchange of fluid between the blood

plasma and the interstitial fluid. 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.

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Functions of Blood – Maintenance of Fluid Levels To maintain balance of fluid exchange

between the blood and the interstitial fluid, blood contains compounds (such as salts and some proteins) to prevent excess fluid loss in the plasma.

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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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Components of Plasma Complex mixture of water, proteins, and other

solutes. When the proteins are moved from plasma,

the remaining fluid is termed serum. 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.

6 and 8 grams of protein in a volume of 100 milliliters of blood (referred to as g/dl)

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 of plasma proteins,

forming 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.

Also called 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 Makes up about 4% of all plasma proteins. Responsible for blood clot formation. Following trauma to the walls of blood vessels,

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

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Plasma Proteins – Regulatory Proteins Form a very minor class of plasma proteins.

<1% of total plasma proteins

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

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Solutes Plasma is an extracellular fluid (ECF).

it includes all body fluids that are not found inside cells Plasma is somewhat like interstitial fluid, in that

both have similar concentrations of nutrients, waste products, and electrolytes

Concentration of dissolved oxygen is higher in plasma than in interstitial fluid, because the cells take up and use the oxygen from the interstitial fluid during energy production.

Difference in concentration ensures that oxygen will continue to diffuse from the blood into the tissues.

Difference in concentration ensures that carbon dioxide will readily diffuse from the interstitial fluid into the blood, where it will be carried to the lungs and discharged from the body.

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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 erythrocytes in the blood. Values vary slightly and are dependent on age and sex. Adult males range between 42% and 56% . Females range from 38% to 46%. Childrens’ hematocrit ranges also vary and differ from

adult values. 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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Erythrocytes Mature erythrocytes lack nuclei. Transport oxygen and carbon dioxide to and

from the tissues and the lungs. Lack of nuclei enables them to carry

respiratory gases more efficiently.

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Hemoglobin in Erythrocytes Every erythrocyte is filled with approximately

280 million molecules of a red-pigmented protein called hemoglobin.

Transports oxygen and 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 and the subcutaneous tissue.

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Hemoglobin in Erythrocytes Each hemoglobin molecule consists of four protein building

blocks, called globins. Alpha (a) chains and beta (b) chains. All globin chains contain a nonprotein (or heme) group that

is in the shape of a ring, with an iron (Fe) ion in its center. Oxygen binds to these iron ions for transport in the blood. Each hemoglobin molecule has four iron ions and is capable

of binding four molecules of oxygen. Oxygen binding is fairly weak to ensure rapid attachment

and detachment of oxygen with hemoglobin. Oxygen binds to the hemoglobin when the erythrocytes

pass through the blood vessels of the lungs. It leaves the hemoglobin when the erythrocytes pass

through the blood vessels of body tissues.

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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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Leukocytes Leukocytes help initiate an immune response

and defend the body against invading pathogens.

Leukocytes are true “cells” in that they contain a nucleus and cellular organelles.

Leukocytes also differ from erythrocytes in that they are about 1.5 to 3 times larger, and they do not contain hemoglobin.

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Leukocytes The five types of leukocytes are divided into

two distinguishable classes—granulocytes and agranulocytes—based upon the presence or absence of visible organelles termed specific granules.

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Leukocytes – Granulocytes Neutrophil

60–70% of the total number of leukocytes Eosinophils have reddish, or pink-orange granules in

their cytoplasm. constitute about 2–4% of the total number of leukocytes nucleus usually has two lobes, which are connected by a

thin strand Basophils are

1.5 times larger than erythrocytes least numerous of the granulocytes constitute about 0.5–1% of the total number of leukocytes always exhibit a bilobed nucleus and abundant blue-violet

granules in the cytoplasm

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Leukocytes – Agranulocytes Agranulocytes are leukocytes that have such

small granules in their cytoplasm that they are frequently overlooked upon casual observation—hence the name agranulocyte.

Agranulocytes include both lymphocytes and

monocytes.

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Leukocytes – Agranulocytes -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

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Leukocytes – Agranulocytes - Monocytes Up to three times the diameter of an

erythrocyte. Constitute about 3–8% of all leukocytes. Nucleus is kidney-shaped or U-shaped. Macrophages phagocytize bacteria, cell

fragments, dead cells, and debris.

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Platelets Irregular, membrane-enclosed cellular fragments that are

about 2 micrometers in diameter (less than one-fourth the size of an erythrocyte).

In stained preparations, they exhibit a dark central region. Sometimes called thrombocytes. Continually produced in the red bone marrow by cells

called megakaryocytes. 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 to halt blood flow.