BloodBlood

20072007

Blood = specialized connective Blood = specialized connective tissuetissue

Cells = 45% of bloodCells = 45% of blood– Erythrocytes (red blood cells, RBCs)Erythrocytes (red blood cells, RBCs)– Leukocytes (white blood cells, WBCs)Leukocytes (white blood cells, WBCs)– PlateletsPlatelets

Extracellular matrix of blood = Extracellular matrix of blood = Plasma; 55% of bloodPlasma; 55% of blood

5-6 Liters total blood volume in adult5-6 Liters total blood volume in adult

Functions of BloodFunctions of Blood

Gaseous transport – RBCs carry Gaseous transport – RBCs carry oxygen and carbon dioxideoxygen and carbon dioxide

Transport of metabolites and Transport of metabolites and regulatory molecules (hormones)regulatory molecules (hormones)

Homeostatic regulation of body Homeostatic regulation of body temperature, osmotic balancetemperature, osmotic balance

Transport of cells and antibodies for Transport of cells and antibodies for defense and immunitydefense and immunity

ErythrocytesErythrocytes Most numerous blood cellsMost numerous blood cells Transport OTransport O22 and CO and CO22 via hemoglobin via hemoglobin Only cell in blood stream that remains in Only cell in blood stream that remains in

blood streamblood stream Biconcave disk shape provides large surface Biconcave disk shape provides large surface

area relative to volume, 8 area relative to volume, 8 m in diameterm in diameter Shape maintained by bendable cytoskeletonShape maintained by bendable cytoskeleton In mammals, no nucleus, mitochondria, ER, In mammals, no nucleus, mitochondria, ER,

ribosomes in mature RBCs. All expelled ribosomes in mature RBCs. All expelled during development.during development.

120-day life span; destroyed by 120-day life span; destroyed by macrophages in spleen and bone marrow.macrophages in spleen and bone marrow.

ErythrocytesErythrocytes

Relative Size of Blood CellsRelative Size of Blood Cells

Leukocytes = White Blood Leukocytes = White Blood CellsCells Granulocytes = neutrophils, eosinophils, Granulocytes = neutrophils, eosinophils,

basophilsbasophils– Numerous secretory vesicles in cytoplasmNumerous secretory vesicles in cytoplasm– 2 or more lobes to nuclei2 or more lobes to nuclei– Typically short lived (a few days)Typically short lived (a few days)– Die by apoptosis and scavenged by macrophagesDie by apoptosis and scavenged by macrophages

Agranulocytes = lymphocytes and Agranulocytes = lymphocytes and monocytesmonocytes– Single lobed nucleiSingle lobed nuclei– Do NOT have abundant secretory vesiclesDo NOT have abundant secretory vesicles– Circulate for a few days and then invade tissues Circulate for a few days and then invade tissues

and become macrophagesand become macrophages– Rounded in shape when circulating, flattened and Rounded in shape when circulating, flattened and

motile in tissues.motile in tissues.

Leukocyte Cell TypesLeukocyte Cell Types

Neutrophil Eosinophil Basophil Monocyte Lymphocyte

Platelets

Granulocytes Agranulocytes

Neutrophils – 60-70% of Neutrophils – 60-70% of circulating leukocytescirculating leukocytes

Multi-lobed nuclei, 3-5 lobesMulti-lobed nuclei, 3-5 lobes Main function: phagocytosis and destruction Main function: phagocytosis and destruction

of bacteriaof bacteria Motile: large numbers exit the blood stream Motile: large numbers exit the blood stream

early in response to acute bacterial infections.early in response to acute bacterial infections. Granules contain: lysozyme and other Granules contain: lysozyme and other

antimicrobial enzymes, collagenase plus antimicrobial enzymes, collagenase plus others.others.

In females, the nucleus has a drumstick (Barr In females, the nucleus has a drumstick (Barr body), contains the condensed, inactivated body), contains the condensed, inactivated second X chromosome.second X chromosome.

Eosinophils – 2-4% of Eosinophils – 2-4% of circulating leukocytescirculating leukocytes

2-lobed nucleus2-lobed nucleus Principal function: allergic and inflammatory Principal function: allergic and inflammatory

reactions and parasitic infectionsreactions and parasitic infections Often found at sites of chronic inflammation, Often found at sites of chronic inflammation,

commonly in respiratory or digestives tractscommonly in respiratory or digestives tracts Counteract the effects of basophils in allergic Counteract the effects of basophils in allergic

reaction: secrete histaminase which degrades reaction: secrete histaminase which degrades the histamine secreted by basophils.the histamine secreted by basophils.

Prominent eosinophilic granules (red/pink)Prominent eosinophilic granules (red/pink)

Basophils - <1% circulating Basophils - <1% circulating leukocytesleukocytes

Involved in allergic and inflammatory Involved in allergic and inflammatory reactionsreactions

Bilobed nucleusBilobed nucleus Basophilic granules (blue/black Basophilic granules (blue/black

stained) obscure the view of the stained) obscure the view of the nucleusnucleus

Secrete histamine (vasodilation) and Secrete histamine (vasodilation) and heparin (anti-coagulant)heparin (anti-coagulant)

Blood CellsBlood Cells

Lymphocytes – 20-25% Lymphocytes – 20-25% circulating leukoctyescirculating leukoctyes

Variable in size, 6-18 Variable in size, 6-18 m in diameterm in diameter Single, round, heterochromatic nucleusSingle, round, heterochromatic nucleus AgranulocyteAgranulocyte Function in immunityFunction in immunity 2 classes, indistinguishable 2 classes, indistinguishable

morphologicallymorphologically– B cells – humoral (antibody-mediated) B cells – humoral (antibody-mediated)

immune responseimmune response– T cells – mature in thymus, cell-mediated T cells – mature in thymus, cell-mediated

immune responseimmune response

Monocytes – 3-8% circulating Monocytes – 3-8% circulating leukocytesleukocytes

Largest in size of circulating leukocytesLargest in size of circulating leukocytes Large, acentric kidney-shaped nucleusLarge, acentric kidney-shaped nucleus AgranulocyteAgranulocyte Stay in circulation a few days and then Stay in circulation a few days and then

migrate into connective tissue and migrate into connective tissue and differentiate into macrophagesdifferentiate into macrophages

As macrophages: phagocytize and As macrophages: phagocytize and destroy dead cellsdestroy dead cells

Platelets (Thrombocytes)Platelets (Thrombocytes)

Principal function: blood clottingPrincipal function: blood clotting Produced by megakaryocytes in bone Produced by megakaryocytes in bone

marrow –bud off cytoplasm to form marrow –bud off cytoplasm to form platelets.platelets.

2 2 m in diameter (very small) and m in diameter (very small) and anucleateanucleate

10-day life span10-day life span

Relative #s of LeukocytesRelative #s of Leukocytes

Neutrophil > Eosinophil >

Basophil Monocyte >

Lymphocyte >

Platelets