1. 17
Blood: Modified by Dr. Par Mohammadian

2. Blood Composition Blood Fluid connective tissue
Plasma – non-living fluid matrix
Formed elements – living blood "cells" suspended in plasma
Erythrocytes (red blood cells, or RBCs)
Leukocytes (white blood cells, or WBCs)
Platelets
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3. Spun tube of blood yields three layers
Blood Composition
Spun tube of blood yields three layers
Plasma on top (~55%)
Erythrocytes on bottom (~45%)
WBCs and platelets in Buffy coat (< 1%)
Hematocrit
Percent of blood volume that is RBCs
47% ± 5% for males; 42% ± 5% for females
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4. Figure 17.1 The major components of whole blood.
Slide 1
Formed
elements
Plasma
• 55% of whole blood
• Least dense component
Buffy coat
• Leukocytes and platelets
• <1% of whole blood
Erythrocytes
Withdraw blood
and place in tube. 1
Centrifuge the
blood sample. 2
• 45% of whole blood
(hematocrit)
• Most dense component
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5. Physical Characteristics and Volume
Sticky, opaque fluid with metallic taste
Color varies with O2 content
High O2 - scarlet; Low O2 - dark red
pH 7.35–7.45
~8% of body weight
Average volume
5–6 L for males; 4–5 L for females
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6. Functions of Blood Distribution Functions
Functions include
Distributing substances
Regulating blood levels of substances
Protection
Distribution Functions
Delivering O2 and nutrients to body cells
Transporting metabolic wastes to lungs and kidneys for elimination
Transporting hormones from endocrine organs to target organs

7. Maintaining body temperature by absorbing and distributing heat
Regulation Functions
Maintaining body temperature by absorbing and distributing heat
Maintaining normal pH using buffers; alkaline reserve of bicarbonate ions
Maintaining adequate fluid volume in circulatory system
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8. Protection Functions Preventing blood loss Preventing infection
Plasma proteins and platelets initiate clot formation
Preventing infection
Antibodies
Complement proteins
WBCs
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9. Over 100 dissolved solutes
Blood Plasma
90% water
Over 100 dissolved solutes
Nutrients, gases, hormones, wastes, proteins, inorganic ions
Plasma proteins most abundant solutes
Remain in blood; not taken up by cells
Proteins produced mostly by liver
60% albumin; 36% globulins; 4% fibrinogen
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10. Table 17.1 Composition of Plasma (1 of 2)
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11. Table 17.1 Composition of Plasma (2 of 2)
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12. Albumin 60% of plasma protein Functions Substance carrier Blood buffer
Major contributor of plasma osmotic pressure
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13. Only WBCs are complete cells RBCs have no nuclei or other organelles
Formed Elements
Only WBCs are complete cells
RBCs have no nuclei or other organelles
Platelets are cell fragments
Most formed elements survive in bloodstream only few days
Most blood cells originate in bone marrow and do not divide
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14. Platelets
Erythrocytes
Monocyte
Neutrophils
Lymphocyte

15. Biconcave discs, anucleate, essentially no organelles
Erythrocytes
Biconcave discs, anucleate, essentially no organelles
Diameters larger than some capillaries
Filled with hemoglobin (Hb) for gas transport
Contain plasma membrane protein spectrin and other proteins
Spectrin provides flexibility to change shape
Major factor contributing to blood viscosity

16. Figure 17.3 Structure of erythrocytes (red blood cells).
2.5 µm
Side view (cut)
7.5 µm
Top view
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17. Structural characteristics contribute to gas transport
Erythrocytes
Structural characteristics contribute to gas transport
Biconcave shape—huge surface area relative to volume
>97% hemoglobin (not counting water)
No mitochondria; ATP production anaerobic; do not consume O2 they transport
Superb example of complementarity of structure and function
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18. RBCs dedicated to respiratory gas transport
Erythrocyte Function
RBCs dedicated to respiratory gas transport
Hemoglobin binds reversibly with oxygen
Normal values
Males - 13–18g/100ml; Females - 12–16 g/100ml
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19. Globin composed of 4 polypeptide chains
Hemoglobin Structure
Globin composed of 4 polypeptide chains
Two alpha and two beta chains
Heme pigment bonded to each globin chain
Gives blood red color
Heme's central iron atom binds one O2
Each Hb molecule can transport four O2
Each RBC contains 250 million Hb molecules
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20. Figure 17.4 Structure of hemoglobin.
 Globin chains
Heme
group
 Globin chains
Hemoglobin consists of globin (two alpha and two beta
polypeptide chains) and four heme groups.
Iron-containing heme pigment.
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21. Hemoglobin (Hb) O2 loading in lungs O2 unloading in tissues
Produces oxyhemoglobin (ruby red)
O2 unloading in tissues
Produces deoxyhemoglobin or reduced hemoglobin (dark red)
CO2 loading in tissues
20% of CO2 in blood binds to Hb  carbaminohemoglobin
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22. Blood cell formation in red bone marrow
Hematopoiesis
Blood cell formation in red bone marrow
Composed of reticular connective tissue and blood sinusoids
In adult, found in axial skeleton, girdles, and proximal epiphyses of humerus and femur
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23. Hematopoietic stem cells (Hemocytoblasts)
Hematopoiesis
Hematopoietic stem cells (Hemocytoblasts)
Give rise to all formed elements
Hormones and growth factors push cell toward specific pathway of blood cell development
Committed cells cannot change
New blood cells enter blood sinusoids
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24. Erythropoiesis: Red Blood Cell Production
Stages
Myeloid stem cell transformed into proerythroblast
In 15 days proerythroblasts develop into basophilic, then polychromatic, then orthochromatic erythroblasts, and then into reticulocytes
Reticulocytes enter bloodstream; in 2 days mature RBC
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25. As myeloid stem cell transforms
Erythropoiesis
As myeloid stem cell transforms
Ribosomes synthesized
Hemoglobin synthesized; iron accumulates
Ejection of nucleus; formation of reticulocyte (young RBC)
Reticulocyte ribosomes degraded; Then become mature erythrocytes
Reticulocyte count indicates rate of RBC formation
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26. Figure 17.5 Erythropoiesis: formation of red blood cells.
Stem cell
Committed cell
Developmental pathway
Phase 1
Ribosome synthesis
Phase 2
Hemoglobin accumulation
Phase 3
Ejection of nucleus
Hematopoietic stem
cell (hemocytoblast)
Basophilic
erythroblast
Polychromatic
erythroblast
Orthochromatic
erythroblast
Proerythroblast
Reticulocyte
Erythrocyte
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27. Regulation of Erythropoiesis
Too few RBCs leads to tissue hypoxia
Too many RBCs increases blood viscosity
> 2 million RBCs made per second
Balance between RBC production and destruction depends on
Hormonal controls
Adequate supplies of iron, amino acids, and B vitamins
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28. Hormonal Control of Erythropoiesis
Hormone Erythropoietin (EPO)
Direct stimulus for erythropoiesis
Always small amount in blood to maintain basal rate
High RBC or O2 levels depress production
Released by kidneys (some from liver) in response to hypoxia
Dialysis patients have low RBC counts
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29. Hormonal Control of Erythropoiesis
Causes of hypoxia
Decreased RBC numbers due to hemorrhage or increased destruction
Insufficient hemoglobin per RBC (e.g., iron deficiency)
Reduced availability of O2 (e.g., high altitudes)
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30. Hormonal Control of Erythropoiesis
Effects of EPO
Rapid maturation of committed marrow cells
Increased circulating reticulocyte count in 1–2 days
Some athletes abuse artificial EPO
Dangerous consequences
Testosterone enhances EPO production, resulting in higher RBC counts in males
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31. Figure 17.6 Erythropoietin mechanism for regulating erythropoiesis.
Slide 1
IMBALANCE
Homeostasis: Normal blood oxygen levels
Stimulus:
Hypoxia
(inadequate O2
delivery) due to 1
O2-carrying
ability of blood
rises. 5
IMBALANCE
• Decreased
RBC count
• Decreased amount
of hemoglobin
• Decreased
availability of O2
Enhanced
erythropoiesis
increases RBC count. 4
Kidney (and liver to
a smaller extent)
releases
erythropoietin. 2
Erythropoietin
stimulates red
bone marrow. 3
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32. Dietary Requirements for Erythropoiesis
Nutrients—amino acids, lipids, and carbohydrates
Iron
Available from diet
65% in Hb; rest in liver, spleen, and bone marrow
Free iron ions toxic
Stored in cells as ferritin and hemosiderin
Transported in blood bound to protein transferrin
Vitamin B12 and folic acid necessary for DNA synthesis for rapidly dividing cells (developing RBCs)
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33. Fate and Destruction of Erythrocytes
Life span: 100–120 days
No protein synthesis, growth, division
Old RBCs become fragile; Hb begins to degenerate
Get trapped in smaller circulatory channels especially in spleen
Macrophages engulf dying RBCs in spleen
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34. Fate and Destruction of Erythrocytes
Heme and globin are separated
Iron salvaged for reuse
Heme degraded to yellow pigment bilirubin
Liver secretes bilirubin (in bile) into intestines
Degraded to pigment urobilinogen
Pigment leaves body in feces as stercobilin
Globin metabolized into amino acids
Released into circulation
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35. Figure 17.7 Life cycle of red blood cells.
Slide 1
Low O2 levels in blood stimulate
kidneys to produce erythropoietin. 1 2
Erythropoietin levels rise in blood.
Erythropoietin and necessary
raw materials in blood promote
erythropoiesis in red bone marrow. 3
New erythrocytes
enter bloodstream;
function about 120
days. 4
Aged and damaged
red blood cells are engulfed
by macrophages of spleen,
liver, and bone marrow; the
hemoglobin is broken down. 5
Hemoglobin
Heme
Globin
Bilirubin is
picked up
by the liver.
Iron is stored
as ferritin or
hemosiderin.
Amino
acids
Iron is bound to transferrin
and released to blood
from liver as needed
for erythropoiesis.
Bilirubin is secreted into
intestine in bile where
it is metabolized to
stercobilin by bacteria.
Circulation
Raw materials are
made available in blood
for erythrocyte synthesis. 6
Food nutrients
(amino acids, Fe,
B12, and folic acid)
are absorbed from
intestine and enter
blood.
Stercobilin
is excreted
in feces.
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36. Make up <1% of total blood volume
Leukocytes
Make up <1% of total blood volume
4,800 – 10,800 WBCs/μl blood
Function in defense against disease
Can leave capillaries via diapedesis
Move through tissue spaces by ameboid motion and positive chemotaxis
Leukocytosis: WBC count over 11,000/mm3
Normal response to infection
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37. Leukocytes: Two Categories
Granulocytes – Visible cytoplasmic granules
Neutrophils, eosinophils, basophils
Agranulocytes – No visible cytoplasmic granules
Lymphocytes, monocytes
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38. Granulocytes Granulocytes Larger and shorter-lived than RBCs
Lobed nuclei
Cytoplasmic granules stain specifically with Wright's stain
All phagocytic to some degree
Platelets
Erythrocytes
Monocyte
Neutrophils
Lymphocyte

39. Second most numerous WBC
Lymphocytes
Second most numerous WBC
Large, dark-purple, circular nuclei with thin rim of blue cytoplasm
Mostly in lymphoid tissue (e.g., lymph nodes, spleen); few circulate in blood
Crucial to immunity
Platelets
Erythrocytes
Monocyte
Neutrophils
Lymphocyte
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40. Lymphocytes
Two types
T lymphocytes (T cells) act against virus-infected cells and tumor cells
B lymphocytes (B cells) give rise to plasma cells, which produce antibodies
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41. Abundant pale-blue cytoplasm
Monocytes
Largest leukocytes
Abundant pale-blue cytoplasm
Dark purple-staining, U- or kidney-shaped nuclei
Platelets
Erythrocytes
Monocyte
Neutrophils
Lymphocyte
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42. Leave circulation, enter tissues, and differentiate into macrophages
Monocytes
Leave circulation, enter tissues, and differentiate into macrophages
Actively phagocytic cells; crucial against viruses, intracellular bacterial parasites, and chronic infections
Activate lymphocytes to mount an immune response

43. All leukocytes originate from hemocytoblasts
Leukopoiesis
Production of WBCs
Stimulated by 2 types of chemical messengers from red bone marrow and mature WBCs
Interleukins (e.g., IL-3, IL-5)
Colony-stimulating factors (CSFs) named for WBC type they stimulate (e.g., granulocyte-CSF stimulates granulocytes)
All leukocytes originate from hemocytoblasts
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44. Lymphoid stem cells  lymphocytes Myeloid stem cells  all others
Leukopoiesis
Lymphoid stem cells  lymphocytes
Myeloid stem cells  all others
Progression of all granulocytes
Myeloblast  promyelocyte  myelocyte  band  mature cell
Granulocytes stored in bone marrow
3 times more WBCs produced than RBCs
Shorter life span; die fighting microbes
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45. Progression of agranulocytes differs Monocytes – live several months
Leukopoiesis
Progression of agranulocytes differs
Monocytes – live several months
Share common precursor with neutrophils
Monoblast  promonocyte  monocyte
Lymphocytes – live few hours to decades
Lymphoid stem cell  T lymphocyte precursors (travel to thymus) and B lymphocyte precursors

46. Figure 17.11 Leukocyte formation.
Stem cells
Hematopoietic stem cell
(hemocytoblast)
Myeloid stem cell
Lymphoid stem cell
Committed
cells
Myeloblast
Myeloblast
Myeloblast
Monoblast
B lymphocyte
precursor
T lymphocyte
precursor
Developmental
pathway
Promyelocyte
Promyelocyte
Promyelocyte
Promonocyte
Eosinophilic
myelocyte
Basophilic
myelocyte
Neutrophilic
myelocyte
Eosinophilic
band cells
Basophilic
band cells
Neutrophilic
band cells
Granular
leukocytes
Agranular
leukocytes
Eosinophils
Basophils
Neutrophils
Monocytes
B lymphocytes
T lymphocytes
(a)
(b)
(c)
(d)
(e)
(f)
Some become
Some become
Some become
Macrophages (tissues)
Plasma cells
Effector T cells

47. Cytoplasmic fragments of megakaryocytes
Platelets
Cytoplasmic fragments of megakaryocytes
Blue-staining outer region; purple granules
Granules contain serotonin, Ca2+, enzymes, ADP, and platelet-derived growth factor (PDGF)
Act in clotting process
Normal = 150,000 – 400,000 platelets /ml of blood
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48. Form temporary platelet plug that helps seal breaks in blood vessels
Platelets
Form temporary platelet plug that helps seal breaks in blood vessels
Circulating platelets kept inactive and mobile by nitric oxide (NO) and prostacyclin from endothelial cells lining blood vessels
Age quickly; degenerate in about 10 days
Formation regulated by thrombopoietin
Derive from megakaryoblast
Mitosis but no cytokinesis  megakaryocyte - large cell with multilobed nucleus

49. Figure 17.12 Formation of platelets.
Stem cell
Developmental pathway
Hematopoietic stem
cell (hemocytoblast)
Megakaryoblast
(stage I megakaryocyte)
Megakaryocyte
(stage II/III)
Megakaryocyte
(stage IV)
Platelets
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50. Table 17.2 Summary of Formed Elements of the Blood (1 of 2)
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51. Table 17.2 Summary of Formed Elements of the Blood (2 of 2)
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