Cerebrum
Midbrain
Medulla
Blood plasma
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Chapter 17: Blood
Blood
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Formed elements
fluid connective tissues
plasma
o non-living fluid matrix
formed element-living blood “cells” suspended in
the plasma
o erythrocytes (red blood cells, or rbc’s)
o leukocytes (white blood cells or wbc’s)
o platelets
Blood composition: Hematocrit
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plasma
o 55 % of whole blood
Buffy coat
o Leukocytes and platelets
o <1% of the whole blood
Erythrocytes
o 45% of whole blood
o (hematocrit)
o Different in both sexes
 Male: 47%
 Female: 42%
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Sticky, opaque fluid with metallic taste
Color varies with O2 content
o High O2 - scarlet
o Low O2 – dark red
pH 7.35- 7.45
~8% of body weught
Average volume
o Male: 5-6 L
o Female: 4-5 L
Function of blood
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Distributing substances
Regulating blood levels of substances
o Deals with endocrine system
Protection
o White blood cells
o Immune system
o Antibody
o Clotting factor
White blood cells
o Complete cells
Red blood cells
o Have no nuclei or other organelles
Platelets are cell fragments
Hemoglobin is a protein
Polycythemia- body’s compensation of low oxygen
Erythrocytes
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Biconcave discs, anucleate
Diameter is larger than some capillaries
Contains spectrin
o plasma protein
filled with >97% hemoglobin (Hb)
doesn’t consume oxygen that they carry
Hemoglobin structures
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Physical characteristics and volume
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90% water
Yellow in color
Over 100 dissolved solutes
o Nutrients, gasses hormones, wastes,
proteins, inorganic ions
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Globin
o composed of 4 polypeptide chains
 two alpha and two beta chains
Heme
o pigment bonded to each globin chains
o has Fe (Iron)
Each HB molecule can transport four 02
Hb can carry 20% CO2 but are dissolved in the plasma
Hemoglobin (Hb)
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O2 loading in lungs
o Produces oxyhemoglobin (ruby red)
O2 unloading in tissues
o Produces deoxyhemoglobin or reduced
hemoglobin (dark red)
CO2 loading in tissues
o 20% of CO2 in blood binds to the Hb 
carbaminohemoglobin
Hematopoiesis: blood cell formation
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Hematopoietic stem cells (hemocytoblasts)
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Hormones and growth factors push stem
cells toward specific blood cell
development
Committed cells cannot change
o
Anemia
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This process can take up to 2 weeks
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Measure reticulocytes- to measure blood production
Hormonal control of erythropoiesis
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Hormone Erythropoietin (EPO)
Direct stimulus for erythropoiesis
Always small amount in the blood to maintain
basal rate
Released by kidneys in response to hypoxia
Signals the marrows to produce blood
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Decreases RBC numbers due to hemorrhage
Insufficient hemoglobin per RBC (e.g., Iron
deficiency)
Reduces availability of O2 (e.g., high altitude)
Blood has abnormally low O2 carrying capacity
o Three groups
 Blood loss
 Low RBC production
 High RBC destruction
Thalassemias
o Typically Mediterranean ancestry
o One globin chain absent or faulty
Sickle- cell anemia
o Black people of African malarial belt
o One amino acid wrong in a globin beta
chain
o RBC’s crescent
o Causes immunity to malaria
Leukocytes
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Cause of hypoxia
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Globin metabolized into amino acids
Make up <1% of total blood volume
Function in defense against disease
o Can leave capillaries via diapedesis
o Move through positive chemotaxis
 Taxis- moving
 Chemo- chemical
 Positive- moving toward
Leukocytes: Two Categories
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Granulocytes
o Neutrophils, eosinophils, basophils
Agranulocytes
o Lymphocytes, monocytes
Neutrophils
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Most numerous WBCs
3-6 lobes in nucleus; twice size of RBCs
Very phagocytic— "bacteria slayers"
Eosinophils
Fate and destruction of Erythrocytes
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Bilobed nucleus
Role in allergies, asthma and in modulating
immune response
Life span: 100-120 days
Old RBC’s become fragile; Hb begins to degenerate Basophils
Get trapped in the spleen
 Rarest WBCs
Macrophages engulf dying RBC’s in spleen
 Contain histamine
Heme and globin are separated in the spleen
o acts as vasodilator to attract WBCs to
o Iron salvage for reuse
inflamed sites
o Hehe degraded to yellow pigment
bilirubin; liver secretes it in the bile into
 Are functionally similar to mast cells
intestines
Agranulocytes
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Lack visible cytoplasmic granules
Have spherical or kidney-shaped nuclei
Lymphocytes
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Second most numerous WBC
Mostly in lymphoid tissue; few circulate in blood
Two types
o T lymphocytes (T-cells)
 Kills antibodies and virus
o B lymphocytes (B-cells)
 Marks anti bodies
 Marks virus and antibodies
Monocytes
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Largest leukocytes
Leave circulation, enter tissues, and differentiate
into macrophages
Activate lymphocytes to mount an immune
response
Leukopoiesis
Derive from megakaryoblast
o Mitosis but no cytokinesis 
megakaryocyte
Stem cell Developmental pathway
Hemostasis -Stoppage of Bleeding
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Clotting factors and substances released by
platelets and injured tissues
Three steps
1. Vascular spasm
2. Platelet plug formation
3. Coagulation (blood clotting)
Clotting Process
Step 1 Vascular spasm
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Smooth muscle contracts, causing
vasoconstriction.
Step 2 Platelet plug formation
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Injury to lining of vessel exposes collagen fibers;
platelets adhere.
Platelets release chemicals that make nearby
platelets sticky; platelet-plug forms.
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Production of WBCs
o Stimulated by
 Interleukins
Step 3 Coagulation
 Colony-stimulating factors (CSFs)
 All leukocytes originate from hemocytoblasts
 Fibrin forms a mesh that traps red blood cells and
 Lymphoid stem cells lymphocytes
platelets, forming the clot.
 Myeloid stem cells  all others
o Granulocytes go from Myeloblastmature Coagulation
cell
 Prothrombin activator
 Granulocytes stored in bone marrow
o Prothrombin converted to thrombin
o Thrombin converts fibrinogen  fibrin
Agranulocytes differ
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Monocytes
o live several months
o Share common precursor with neutrophils
o Myeloid stem cells  monocyte
Lymphocytes
o live few hours to decades
o Lymphoid stem cell  T lymphocyte and B
lymphocyte precursors
Platelets
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Cytoplasmic fragments of megakaryocytes
Contain a platelet-derived growth factor (PDGF)
Form temporary plug that seals blood vessels
Circulating platelets kept inactive
Age quickly; degenerate in about 10 days
Clot Retraction
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Stabilizes clot
Actin and myosin in platelets contract blood
vessels’ smooth muscle tissue within 30–60
minutes
Draws ruptured blood vessel edges together
Vessel Repair
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Platelet-derived growth factor (PDGF) stimulates
the rebuild of blood vessel wall
Vascular endothelial growth factor
(VEGF)stimulates endothelial cells to multiply and
restore endothelial lining
Thromboembolic Conditions
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Thrombus
 Type O
o clot that develops and persists in unbroken
o universal donor
blood vessel
o No A or B antigens
o May block circulation leading to tissue
 Type AB
death
o universal recipient
Embolus
o No anti-A or anti-B antibodies
o thrombus freely floating in bloodstream
Blood being tested Serum
Embolism
o embolus obstructing a vessel
o e.g., pulmonary and cerebral emboli
Human Blood Groups
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blood cells has protein attached outside the RBC
RBC membranes bear 30 types of glycoprotein
antigens
o Promoters of agglutination; called
agglutinogens
Mismatched transfused blood perceived as foreign
Presence or absence of each antigen is used to
classify blood groups : ABO and Rh
ABO Blood Groups
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Types A, B, AB, and O
Based on presence or absence of two
agglutinogens (A and B) on surface of RBC’s
Rh Blood Groups
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52 named Rh agglutinogens (Rh factors)
C, D, and E are most common
Rh+ indicates presence of D antigen
o 85% Americans Rh+
Anti-Rh+ antibodies not spontaneously formed in
Rh– individuals
o form if Rh– individual receives Rh+ blood,
or Rh– mom carrying Rh+ fetus
Second exposure
Transfusions