14.1: Introduction
Blood:
• Is connective tissue
• Transports vital substances
• Maintains stability of interstitial fluid
• Distributes heat
Blood cells:
• Form in red bone marrow
• Red blood cells (RBCs)
• White blood cells (WBCs)
• Platelets (cell fragments)
• The amount of blood varies with body size, changes in fluid concentration, changes in
electrolyte concentration, and amount of adipose tissue
• Blood is about 8% of body weight
• Adult blood volume is about 5 liters
1
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Capillary tube
Plasma = 55%
Buffy coat
Red cells = 45%
(hematocrit)
Plug
2
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Blood
45%
55%
Formed elements
Plasma
Platelets
Red blood cells
White blood cells
(4.8%)
(95.1%)
(0.1%)
Electrolytes
Water
(92%)
Proteins
Wastes
Nutrients
Gases
(7%)
Vitamins
Hormones
Neutrophils
Eosinophils
Basophils
(54–62%)
(1–3%)
(<1%)
Monocytes
(3–9%)
Lymphocytes
Albumins
Globulins
Fibrinogen
N2
O2
CO2
(25–33%)
3
14.2: Blood Cells
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Hematopoietic stem cell
Hemocytoblast
Lymphoid stem cell
Myeloid stem cell
Myeloblast
Proerythroblast
Monoblast
In red bone marrow
Megakaryoblast
Lymphoblast
T cell
precursor
Lymphoblast
B cell
precursor
Progranulocyte
Erythroblast
Neutrophilic
myelocyte
Basophilic
myelocyte
Neutrophilic
band cell
Basophilic
band cell
Neutrophil
Basophil
Eosinophilic
myelocyte
Promonocyte
Prolymphocyte
Prolymphocyte
T lymphocyte
B lymphocyte
Normoblast
Megakaryocyte
Eosinophilic
band cell
Erythrocyte
Thrombocytes
(platelets)
Eosinophil
Monocyte
Granulocytes
Activated in tissues
(some cells)
In circulating blood
Reticulocyte
Agranulocytes
Macrophage
(a)
(b)
© The McGraw-Hill Companies, Inc./Al Telser, photographer
Plasma cell
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The Origin of Blood Cells
• Blood cells originate in red marrow from hemocytoblasts or hematopoietic stem
cells
• Stem cells can then:
• Give rise to more stem cells
• Specialize or differentiate when responding to hematopoietic growth factors
• Lymphoid stem cells
• Myeloid stem cells
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Characteristics of Red Blood Cells
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Red blood cells are:
• Erythrocytes
• Biconcave discs
• One-third hemoglobin or:
• Oxyhemoglobin
• Deoxyhemoglobin
Top view
7.5 micrometers
2.0 micrometers
Sectional view
(a)
• Able to readily squeeze through capillaries
• Lack nuclei and mitochondria
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(b)
b: © Bill Longcore/Photo Researchers, Inc.
Red Blood Cell Counts
• RBC counts is the number of RBCs in a cubic millimeter or microliter of blood
• It may vary depending on age and health
• Typical ranges include:
• 4,600,000 – 6,200,000 in males
• 4,200,000 – 5,400,000 in adult females
• 4,500,000 – 5,100,000 in children
• RBC counts reflects blood’s oxygen carrying capacity
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Red Blood Cell Production
and Its Control
• Erythropoiesis
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• Low blood oxygen causes the kidneys and the
liver to release erythropoietin (EPO) which
stimulates RBC production
Low blood oxygen
Liver
Kidney
Release into
bloodstream
Stimulation
Inhibition
–
• This is a negative feedback mechanism
•Hemocytoblast→erythroblasts→reticulocytes
→erythrocytes
•Within a few days many new blood cells
appear in the circulating blood
Erythropoietin
Bloodstream
+
Red bone marrow
Increased
oxygencarrying
capacity
Increased
number of
red blood
cells
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Dietary Factors Affecting Red Blood
Cell Production
• Vitamin B12 and folic acid are necessary
• They are required for DNA synthesis making them necessary for the growth and division
of all cells
• Iron is also necessary
• It is required for hemoglobin synthesis
9
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Red bone
marrow
Bone
3 Red blood
cells produced
4 Red blood cells
circulate in
bloodstream for
about 120 days
5
Macrophage
Nutrients
from food
2 Blood transports
absorbed nutrients
Vitamin B12
Folic acid
Iron
Old red
blood cells
Absorption
1
6 Hemoglobin
Blood
Globin + Heme
7 Iron + Biliverdin
Liver
Small
intestine
Bile
Bilirubin
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Types of White Blood Cells
• Leukocytes: White blood cells that Protect against disease
•WBC hormones are interleukins and colony-stimulating factors which stimulate development
•There are 5 types of WBCs in 2 categories:
• Granulocytes
1. Neutrophils  1st to arrive at infections
2. Eosinophils  elevated in worm infestation (defends) & allergic reaction
3. Basophils  Releases Histamine & Heparin
• Agranulocytes
4. Lymphocytes  T cells or B cells. B cells produce antibodies
5. Monocytes Phagocytize bacteria, dead cells, and other debris
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Neutrophils
• Light purple granules in acid-base stain with Lobed nucleus
•Other names
• Segs
• Polymorphonuclear leukocyte
• Bands (young neutrophils)
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• First to arrive at infections
• Phagocytic
© Ed Reschke
• 54% - 62% of leukocytes
• Elevated in bacterial infections
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Eosinophils
• Deep red granules in acid stain
• Bi-lobed nucleus
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• Moderate allergic reactions
• Defend against parasitic worm infestations
• 1% - 3% of leukocytes
• Elevated in parasitic worm infestations and
allergic reactions
© Ed Reschke
13
Basophils
• Deep blue granules in basic
stain
• Release histamine
• Release heparin
• Less than 1% of leukocytes
• Similar to eosinophils in
size and shape of nuclei
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© Ed Reschke
14
Monocytes
• Largest of all blood cells
• Spherical, kidney-shaped, oval or lobed nuclei
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• Leave bloodstream to become macrophages
• 3% - 9% of leukocytes
• Phagocytize bacteria, dead cells, and other debris
© R. Kessel/Visuals Unlimited
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Lymphocytes
• Slightly larger than RBC
• Large spherical nucleus surrounded by thin rim of cytoplasm
• T cells and B cells
• Both important in immunity
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• B cells produce antibodies
• 25% - 33% of leukocytes
© Ed Reschke
16
Functions of White Blood Cells
• WBCs protect against infection
• These leukocytes can squeeze between the cells of a capillary wall and enter the
tissue space outside the blood vessel (called diapedesis)
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Connective
tissue
Blood capillary
Leukocyte
17
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1 Splinter
punctures
epidermis
2 Bacteria are introduced
into the dermis
3 Bacteria
multiply
4 Injured cells
release histamine,
causing blood
vessels to dilate
Epidermis
Dermis
Blood vessels
5 Neutrophils move through
blood vessel walls and
migrate toward bacteria
6 Neutrophils destroy
bacteria by phagocytosis
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White Blood Cell Counts
• A procedure used to count number of WBCs per cubic millimeter of blood
• Typically 5,000 – 10,000 per cubic millimeter of blood
•Leukopenia:
• Low WBC count (below 5,000)
• Typhoid fever, flu, measles, mumps, chicken pox, AIDS
• Leukocytosis:
• High WBC count (above 10,000)
• Acute infections, vigorous exercise, great loss of body fluids
• Differential WBC count
• Lists percentages of types of leukocytes
• May change in particular diseases
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20
Blood Platelets
•Throytmboces also known as Platelets
• They are cell fragments of megakaryocytes
• Produced by hemocytoblasts in response to thrombopoietin
• hemocytoblast→megakaryocyte→thrombocytes
• They lack a nucleus and are roughly half the size of a RBC
• There are approximately 150,000 – 450,000 per cubic millimeter of blood
• They help repair damaged blood vessels by sticking to broken surfaces
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• They release seratonin, which causes smooth muscles in walls of blood vessels to contract
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14.3: Blood Plasma
• Blood plasma is:
• Straw colored
• The liquid portion of blood
• 55% of blood volume
• 92% water
• Includes transporting nutrients, gases, and vitamins
• Helps regulate fluid and electrolyte balance and maintain pH
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Plasma Proteins
• These are the most abundant dissolved substances (solutes) in plasma
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Gases and Nutrients
• The most important blood gases:
• Oxygen
• Carbon dioxide
• Plasma nutrients include:
• Amino acids
• Simple sugars
• Nucleotides
• Lipids
• Fats (triglycerides)
• Phospholipids
• Cholesterol
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Nonprotein Nitrogenous Substances
• These are molecules containing nitrogen but are not proteins
• In plasma they include:
• Urea – product of protein catabolism; about 50% of nonprotein nitrogenous substances
• Uric acid – product of nucleic acid catabolism
• Amino acids – product of protein catabolism
• Creatine – stores phosphates
• Creatinine – product of creatine metabolism
• BUN – blood urea nitrogen; indicates health of kidney’
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Plasma Electrolytes
• Plasma contains a variety of these ions called electrolytes
• They are absorbed from the intestine or released as by-products of cellular metabolism
• They include:
• Sodium (most abundant with chloride)
• Potassium
• Calcium
• Magnesium
• Chloride (most abundant with sodium)
• Bicarbonate
• Phosphate
• Sulfate
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14.4: Hemostasis
• Hemostasis refers to the stoppage of bleeding
• Actions that limit or prevent blood loss include:
• Blood vessel spasm
• Platelet plug formation
• Blood coagulation
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Blood Vessel Spasm
• Blood vessel spasm
• Triggered by pain receptors, platelet release, or serotonin
• Smooth muscle in blood vessel contracts
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Platelet Plug Formation
• Platelet plug formation
• Triggered by exposure of platelets to collagen
• Platelets adhere to rough surface to form a plug
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Endothelial lining
Collagen fiber
1 Break in
vessel wall
Platelet
Red blood cell
2 Blood escaping
through break
3 Platelets adhere to each other,
to end of broken vessel, and to
exposed collagen
4
Platelet plug
helps control
blood loss
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Blood Coagulation
• Blood coagulation
• Triggered by cellular damage and blood contact with foreign surfaces
•A blood clot forms as soluble fibrinogen changes to insoluble threads of fibrin, which trap
blood cells
• Hemostatic mechanism
• Causes the formation of a blot clot via a series of reactions which activates the next in a
cascade
• Occurs extrinsically or intrinsically
• Requires clotting factors and vit. K
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Extrinsic Clotting Mechanism
• Extrinsic clotting mechanism
• Chemical outside of blood vessel triggers blood coagulation
•Triggered by tissue thromboplastin (factor III) (not found in blood)
• A number of events occur that includes factor VII, factor X, factor V, factor IV, and factor II
(prothrombin)
• Triggered when blood contacts damaged blood vessel walls or tissues
• This is an example of a positive feedback mechanism
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Intrinsic Clotting Mechanism
• Intrinsic clotting mechanism
• Chemical inside blood triggers blood coagulation
•Triggered by Hageman factor XII (found inside blood)
• Factor XII activates factor XI which activates IX which joins with factor VIII to activate
factor X
• Triggered when blood contacts a foreign surface
35
36
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Extrinsic Clotting
Mechanism
Intrinsic Clotting
Mechanism
Tissue damage
Blood contacts
foreign surface
Releases
Activates
Tissue thromboplastin
(Factor lll)
Activates
Hageman Factor Xll
(Ca+2)
Activates
Factor Vll
Activates
Factor Xl
(Ca+2)
Activates
Factor X
Factor lX
Activates
Factor Vlll
platelet phospholipids
Factor V
(Ca+2)
Activates
Factor X
(Ca+2)
Activates
Factor V
(Ca+2)
Prothrombin
activator
Converts
Prothrombin
(Factor ll)
Thrombin
(Factor lla)
Converts
Fibrinogen
(Factor l)
Fibrin
Factor Xlll
Stabilizes
Fibrin
clot
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Fate of Blood Clots
• After a blood clot forms it retracts and pulls the edges of a broken blood vessel together (to
repair) while squeezing the fluid serum from the clot
•Platelet-derived growth factor stimulates smooth muscle cells and fibroblasts to repair damaged
blood vessel walls
• Plasmin (enzyme) digests the blood clots
• A thrombus is an abnormal blood clot (very difficult to digest)
• An embolus is a blood clot moving through the blood vessels (can cause damage to the heart)
38
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Lumen
(a)
Artery wall
Lumen
Plaque
Artery wall
(b)
© The McGraw-Hill Companies, Inc./Al Telser, photographer
39
Prevention of Coagulation
• The smooth lining of blood vessels discourages the accumulation of platelets and clotting factors
(fibrinagin)
•As a clot forms fibrin adsorbs thrombin and prevents the clotting reaction from spreading
• Anti-thrombin inactivates additional thrombin by binding to it and blocking its action on
fibrinogen
• Some cells such as basophils and mast cells secrete heparin (an anticoagulant)
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14.5: Blood Groups
and Transfusions
• In 1910, identification of the ABO blood antigen gene explained the observed blood type
incompatibilities
• Today there are 31 different genes known to contribute to the surface features of RBCs
determining compatibility between blood types
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Antigens and Antibodies
• Terms to become familiar with:
• Agglutination – clumping of red blood cells in response to a reaction between an antibody
and an antigen
• Antigens – a chemical that stimulates cells to produce antibodies
• Antibodies – a protein that reacts against a specific antigen
42
ABO Blood Group
• Based on the presence or absence of two major antigens on red blood cell membranes
• Antigen A
• Antigen B
43
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Red blood cell
Anti-B antibody
Red blood cell
Anti-A antibody
Antigen A
Antigen B
Type A blood
Red blood cell
Type B blood
Anti-A antibody
Anti-B antibody
Antigen A
Antigen B
Red blood cell
Type AB blood
Type O blood
44
ABO Blood Group
• When blood cells come in contact with non-compatible antibodies, they will
agglutinate (clump together)
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Red blood cell
Agglutinated red
blood cells
Antigen A
Anti-B antibody
Anti-A antibody
(a)
(c)
(b)
(d)
c: © G.W. Willis/Visuals Unlimited; d: © George W. Wilder/Visuals Unlimited
45
• The Rh blood group was named for the rhesus monkey
• The group includes several Rh antigens or factors
• Rh positive – presence of antigen D or other Rh antigens on
the red blood cell membranes
Wilder/Visuals Unlim
• Rh negative – lack of these antigens
• Anti-Rh antibodies form only in Rh-negative individuals in
response to the presence of red blood cells with Rh antigens
• The seriousness of the Rh blood group is evident in a fetus
that develops the condition erythroblastosis fetalis or
hemolytic disease of the newborn
ABO Blood Group
• Type 0– universal donor
• Type AB – universal recipient
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– – –
– – –
– ––
–
–
–
– – –
–
– –
–
–
– – –– – –
– – –
–
– – – –
–
– –
–
+
– –
–
–
+
+
– –
+ + +
–
+
–
+
–
+
– –
–
–
Rh-negative
woman with
Rh-positive
fetus
–– –
– – –
– – –
– ––
–
–
–
– – –
–
– –
–
–
– – –– – –
– – –
–
– – ++ +
–
++
–
+
–
+
+
+
– +
+ + +
+
+
–
+
–
+
+
– +
–
–
Cells from
Rh-positive
fetus enter
woman’s
bloodstream
–––
– – ––
–
– –
– –
–
–
–
– – ––
– – – –
– – – –– –
–
– ––
– – ––
–
–
– –
– – –
–
–
–
–
–
–
–
– +
–
–
– –
–
–
–
Woman
becomes
sensitized—
antibodies ( + )
form to fight
Rh-positive
blood cells
–––
– – ––
–
– –
– –
–
–
–
– – ––
– – – –
– – – –– –
–
– ––
– – ––
–
–
– –
– –
–
–
–
–
–
–
–
–
–
–
–
In the next
Rh-positive
pregnancy,
maternal
antibodies
attack fetal red
blood cells
48