Transcript Blood and Blood Cell Development

Blood
2007
Blood = specialized connective
tissue
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Cells = 45% of blood
– Erythrocytes (red blood cells, RBCs)
– Leukocytes (white blood cells, WBCs)
– Platelets
Extracellular matrix of blood = Plasma;
55% of blood
 5-6 Liters total blood volume in adult
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Functions of Blood
Gaseous transport – RBCs carry oxygen
and carbon dioxide
 Transport of metabolites and regulatory
molecules (hormones)
 Homeostatic regulation of body
temperature, osmotic balance
 Transport of cells and antibodies for
defense and immunity
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Erythrocytes
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Most numerous blood cells
Transport O2 and CO2 via hemoglobin
Only cell in blood stream that remains in blood
stream
Biconcave disk shape provides large surface area
relative to volume, 8 mm in diameter
Shape maintained by bendable cytoskeleton
In mammals, no nucleus, mitochondria, ER,
ribosomes in mature RBCs. All expelled during
development.
120-day life span; destroyed by macrophages in
spleen and bone marrow.
Erythrocytes
Relative Size of Blood Cells
Leukocytes = White Blood Cells
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Granulocytes = neutrophils, eosinophils,
basophils
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Numerous secretory vesicles in cytoplasm
2 or more lobes to nuclei
Typically short lived (a few days)
Die by apoptosis and scavenged by macrophages
Agranulocytes = lymphocytes and monocytes
– Single lobed nuclei
– Do NOT have abundant secretory vesicles
– Circulate for a few days and then invade tissues and
become macrophages
– Rounded in shape when circulating, flattened and
motile in tissues.
Leukocyte Cell Types
Agranulocytes
Granulocytes
Neutrophil
Eosinophil
Basophil
Monocyte
Platelets
Lymphocyte
Neutrophils – 60-70% of circulating
leukocytes
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Multi-lobed nuclei, 3-5 lobes
Main function: phagocytosis and destruction of
bacteria
Motile: large numbers exit the blood stream
early in response to acute bacterial infections.
Granules contain: lysozyme and other
antimicrobial enzymes, collagenase plus others.
In females, the nucleus has a drumstick (Barr
body), contains the condensed, inactivated
second X chromosome.
Eosinophils – 2-4% of circulating
leukocytes
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2-lobed nucleus
Principal function: allergic and inflammatory
reactions and parasitic infections
Often found at sites of chronic inflammation,
commonly in respiratory or digestives tracts
Counteract the effects of basophils in allergic
reaction: secrete histaminase which degrades
the histamine secreted by basophils.
Prominent eosinophilic granules (red/pink)
Basophils - <1% circulating
leukocytes
Involved in allergic and inflammatory
reactions
 Bilobed nucleus
 Basophilic granules (blue/black stained)
obscure the view of the nucleus
 Secrete histamine (vasodilation) and
heparin (anti-coagulant)
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Blood Cells
Lymphocytes – 20-25% circulating
leukoctyes
Variable in size, 6-18 mm in diameter
 Single, round, heterochromatic nucleus
 Agranulocyte
 Function in immunity
 2 classes, indistinguishable morphologically
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– B cells – humoral (antibody-mediated) immune
response
– T cells – mature in thymus, cell-mediated
immune response
Monocytes – 3-8% circulating
leukocytes
Largest in size of circulating leukocytes
 Large, acentric kidney-shaped nucleus
 Agranulocyte
 Stay in circulation a few days and then
migrate into connective tissue and
differentiate into macrophages
 As macrophages: phagocytize and
destroy dead cells
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Platelets (Thrombocytes)
Principal function: blood clotting
 Produced by megakaryocytes in bone
marrow –bud off cytoplasm to form
platelets.
 2 mm in diameter (very small) and
anucleate
 10-day life span
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Relative #s of Leukocytes
Neutrophil >
Lymphocyte >
Monocyte >
Eosinophil >
Platelets
Basophil