Chapter 18
*Lecture Animation
Outline
The Circulatory
System: Blood
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Introduction
• Many myths about blood
– Mysterious “vital force”
– Drained “bad-blood” for medical reasons
– Hereditary traits were once thought to be transmitted
through blood
• Blood cells were seen with the first microscopes
• Hematology—the study of blood
• Recent developments in this field help save lives
18-2
Introduction
• Expected Learning Outcomes
– Describe the functions and major components of the
circulatory system.
– Describe the components and physical properties of
blood.
– Describe the composition of blood plasma.
– Explain the significance of blood viscosity and osmolarity.
– Describe in general terms how blood is produced.
18-3
Functions of the Circulatory System
• Circulatory system consists of the heart, blood
vessels, and blood
• Cardiovascular system refers only to the heart
and blood vessels
• Hematology—the study of blood
• Functions of circulatory system
– Transport
• O2, CO2, nutrients, wastes, hormones, and stem cells
– Protection
• Inflammation, limit spread of infection, destroy
microorganisms and cancer cells, neutralize toxins, and
initiate clotting
– Regulation
• Fluid balance, stabilizes pH of ECF, and temperature control
18-4
Components and General Properties
of Blood
• Adults have 4 to 6 L of blood
• A liquid connective tissue consisting of cells
and extracellular matrix
– Plasma: matrix of blood
• Clear, light yellow fluid
– Formed elements: blood cells and cell
fragments
• Red blood cells, white blood cells, and platelets
18-5
Components and General Properties
of Blood
• Seven kinds of formed elements
– 1)Erythrocytes: red blood cells (RBCs)
– 2)Platelets
• Cell fragments from special cell in bone marrow
– Leukocytes: white blood cells (WBCs)
• Five leukocyte types divided into two categories
• Granulocytes (with granules)
– 3)Neutrophils
– 4)Eosinophils
– 5)Basophils
• Agranulocytes (without granules)
– 6)Lymphocytes
– 7)Monocytes
18-6
Components and General Properties
of Blood
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Monocyte
Small
lymphocyte
Neutrophil
Platelets
Eosinophil
Small
lymphocyte
Erythrocyte
Young (band)
neutrophil
Neutrophil
Monocyte
Large
lymphocyte
Neutrophil
Basophil
Figure 18.1
18-7
Blood Plasma
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Withdraw
blood
Centrifuge
Plasma
(55% of whole blood)
Buffy coat: leukocytes
and platelets
(<1% of whole blood)
Erythrocytes
(45% of whole blood)
Figure 18.2
Formed
elements
• Hematocrit—centrifuge blood to
separate components
– Erythrocytes are heaviest and
settle first
• 37% to 52% total volume
– White blood cells and platelets
• 1% total volume
• Buffy coat
– Plasma
• The remainder of volume
• 47% to 63%
• Complex mixture of water,
proteins, nutrients,
electrolytes, nitrogenous
wastes, hormones, and gases
18-8
Blood Plasma
• Plasma—liquid portion of blood
– Serum: remaining fluid when blood clots and the solids are
removed
• Identical to plasma except for the absence of fibrinogen
• Three major categories of plasma proteins
– Albumins: smallest and most abundant
• Contribute to viscosity and osmolarity; influence blood pressure,
flow, and fluid balance
– Globulins (antibodies)
• Provide immune system functions
• Alpha, beta, and gamma globulins
– Fibrinogen
• Precursor of fibrin threads that help form blood clots
18-9
Blood Plasma
• Plasma proteins formed by liver
– Except globulins (produced by plasma cells)
• Nitrogenous compounds
– Free amino acids
• From dietary protein or tissue breakdown
– Nitrogenous wastes (urea)
• Toxic end products of catabolism
• Normally removed by the kidneys
18-10
Blood Plasma
• Nutrients
– Glucose, vitamins, fats, cholesterol, phospholipids,
and minerals
• Dissolved O2, CO2, and nitrogen
• Electrolytes
– Na+ makes up 90% of plasma cations
18-11
Blood Viscosity and Osmolarity
• Viscosity—resistance of a fluid to flow, resulting
from the cohesion of its particles
– Whole blood 4.5 to 5.5 times as viscous as water
– Plasma is 2.0 times as viscous as water
• Important in circulatory function
18-12
Blood Viscosity and Osmolarity
• Osmolarity of blood—the total molarity of those
dissolved particles that cannot pass through the
blood vessel wall
– If too high, blood absorbs too much water, increasing
the blood pressure
– If too low, too much water stays in tissue, blood
pressure drops, and edema occurs
– Optimum osmolarity is achieved by the body’s
regulation of sodium ions, proteins, and red blood cells
18-13
Starvation and Plasma
Protein Deficiency
• Hypoproteinemia
– Deficiency of plasma proteins
• Extreme starvation
• Liver or kidney disease
• Severe burns
• Kwashiorkor
– Children with severe protein deficiency
• Fed on cereals once weaned
– Thin arms and legs
– Swollen abdomen
18-14
How Blood Is Produced
• Adult production of 400 billion platelets, 200 billion
RBCs, and 10 billion WBCs every day
• Hemopoiesis—production of blood, especially its
formed elements
• Hemopoietic tissues produce blood cells
– Yolk sac produces stem cells for first blood cells
• Colonize fetal bone marrow, liver, spleen, and thymus
– Liver stops producing blood cells at birth
– Spleen remains involved with lymphocyte production
18-15
How Blood is Produced
– Red bone marrow produces all seven formed
elements
• Pluripotent stem cells (PPSC)
– Formerly called hemocytoblasts or hemopoietic
stem cells
• Colony-forming units—specialized stem cells
only producing one class of formed element of
blood
• Myeloid hemopoiesis—blood formation in the
bone marrow
• Lymphoid hemopoiesis—blood formation in
the lymphatic organs
18-16
Erythrocytes
• Expected Learning Outcomes
– Discuss the structure and function of erythrocytes
(RBCs).
– Describe the structure and function of hemoglobin.
– State and define some clinical measurements of RBC
and hemoglobin quantities.
– Describe the life cycle of erythrocytes.
– Name and describe the types, causes, and effects of
RBC excesses and deficiencies.
18-17
Erythrocytes
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Capillary
wall
Erythrocytes
Figure 18.4c
(c)
7 µm
© Dr. Don W. Fawcett/Visuals Unlimited
• Two principal functions
– Carry oxygen from lungs to cell tissues
– Pick up CO2 from tissues and bring to lungs
• Insufficient RBCs may kill in minutes due to lack of oxygen
to tissues
18-18
Form and Function
• Disc-shaped cell with thick rim
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Surface view
– 7.5 m diameter and 2.0 m
thick
at rim
– Lose nearly all organelles
during development
• Lack mitochondria
– Anaerobic fermentation to
produce ATP
• Lack of nucleus and DNA
– No protein synthesis or
mitosis
7.5 µm
2.0 µm
(a)
Sectional view
Figure 18.4a
18-19
Form and Function
– Blood type determined by surface glycoprotein and
glycolipids
– Cytoskeletal proteins (spectrin
and actin) give membrane
durability and resilience
• Stretch and bend as squeezed through small capillaries
18-20
Form and Function
• Gas transport—major function
– Increased surface area/volume ratio
• Due to loss of organelles during maturation
• Increases diffusion rate of substances
– 33% of cytoplasm is hemoglobin (Hb)
• 280 million hemoglobin molecules on one RBC
• O2 delivery to tissue and CO2 transport to lungs
• Carbonic anhydrase (CAH) in cytoplasm
– Produces carbonic acid from CO2 and water
– Important role in gas transport and pH balance
18-21
Hemoglobin
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• Each Hb molecule consists of:
– Four protein chains—globins
– Four heme groups
Beta
Alpha
Heme
groups
(a)
Beta
Alpha
• Heme groups
CH3 CH
C
– Nonprotein moiety that binds O2
to ferrous ion (Fe2+) at its center
HC
CH3
C
C
N
CH2
C
C
HC
CH
C
Fe2+
N
CH2
C
C
C
CH2
C
CH3
C
CH
N
C
N
C
C
CH2
CH
COOH
C
C
CH2
CH3
CH2
COOH
(b)
Figure 18.5a,b
18-22
Hemoglobin
• Globins—four protein chains
– Two alpha and two beta chains
– 5% CO2 in blood is bound to globin moiety
• Adult vs. fetal hemoglobin
18-23
Quantities of Erythrocytes
and Hemoglobin
• RBC count and hemoglobin concentration
indicate amount of O2 blood can carry
– Hematocrit (packed cell volume): percentage of
whole blood volume composed of RBCs
• Men 42% to 52% cells; women 37% to 48% cells
– Hemoglobin concentration of whole blood
• Men 13 to 18 g/dL; women 12 to 16 g/dL
– RBC count
• Men 4.6 to 6.2 million/L; women 4.2 to 5.4
million/L
18-24
Quantities of Erythrocytes
and Hemoglobin
• Values are lower in women
– Androgens stimulate RBC production
– Women have periodic menstrual losses
– Hematocrit is inversely proportional to percentage of
body fat
18-25
Erythrocyte Production
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Pluripotent
stem cell
Colony-forming
unit (CFU)
Erythrocyte CFU
Precursor
cells
Erythroblast
Mature
cell
Reticulocyte
Erythrocyte
Figure 18.6
• 2.5 million RBCs are produced per second
• Average lifespan of about 120 days
• Development takes 3 to 5 days
– Reduction in cell size, increase in cell number, synthesis
of hemoglobin, and loss of nucleus
18-26
Erythrocyte Production
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Pluripotent
stem cell
Colony-forming
unit (CFU)
Erythrocyte CFU
Precursor
cells
Erythroblast
Mature
cell
Reticulocyte
Erythrocyte
Figure 18.6
• First committed cell—erythrocyte colony-forming unit
– Has receptors for erythropoietin (EPO) from kidneys
• Erythroblasts (normoblast) multiply and synthesize
hemoglobin
• Nucleus discarded to form a reticulocyte
– Named for fine network of endoplasmic reticulum
– 0.5% to 1.5% of circulating RBCs are reticulocytes
18-27
Iron Metabolism
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leaves
8 Remaining transferrin is distributed
to other organs where Fe2+ is used
to make hemoglobin, myoglobin, etc.
7 Fe2+ binds to
apoferritin
to be stored
as ferritin
1 Mixture of Fe2+ and
Fe3+ is ingested
Fe3+
2 Stomach acid
converts Fe3+
to Fe2+
Ferritin
Fe2+
Apoferritin
Gastroferritin
6 In liver, some transferrin
releases Fe2+ for storage
Blood plasma
5 In blood plasma,
Fe2+ binds to transferrin
Transferrin
3 Fe2+ binds to
gastroferritin
4 Gastroferritin transports
Fe2+ to small intestine and
releases it for absorption
Figure 18.7
18-28
Iron Metabolism
• Iron—key nutritional requirement
– Lost daily through urine, feces, and bleeding
• Men 0.9 mg/day and women 1.7 mg/day
– Low absorption rate of iron requires consumption
of 5 to 20 mg/day
18-29
Iron Metabolism
• Dietary iron: ferric (Fe3+) and ferrous (Fe2+)
– Stomach acid converts Fe3+ to absorbable Fe2+
– Gastroferritin binds Fe2+ and transports it to small
intestine
– Absorbed into blood and binds to transferrin for
transport to bone marrow, liver, and other tissues
- Bone marrow for hemoglobin, muscle for myoglobin,
and all cells use for cytochromes in mitochondria
• Liver apoferritin binds to create ferritin for
storage
18-30
Iron Metabolism
• Vitamin B12 and folic acid
– Rapid cell division and DNA synthesis that occurs in
erythropoiesis
• Vitamin C and copper
– Cofactors for enzymes synthesizing hemoglobin
• Copper is transported in the blood by an alpha globulin called
ceruloplasmin
18-31
Erythrocyte Homeostasis
• Negative feedback control
– Drop in RBC count causes kidney
hypoxemia
– Kidney production of
erythropoietin stimulates bone
marrow
– RBC count increases in 3 to 4
days
• Stimuli for increasing
erythropoiesis
–
–
–
–
Low levels O2 (hypoxemia)
High altitude
Increase in exercise
Loss of lung tissue in emphysema
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Hypoxemia
(inadequate O2 transport)
Increased
O2 transport
Sensed by liver and kidneys
leaves
Increased
RBC count
Accelerated
erythropoiesis
Secretion of
erythropoietin
Stimulation of
red bone marrow
Figure 18.8
18-32
Erythrocyte Death and Disposal
• RBCs lyse in narrow channels in spleen
• Macrophages in spleen
– Digest membrane bits
– Separate heme from globin
• Globins hydrolyzed into amino acids
• Iron removed from heme
– Heme pigment converted to biliverdin (green)
– Biliverdin converted to bilirubin (yellow)
– Released into blood plasma (kidneys—yellow urine)
– Liver removes bilirubin and secretes into bile
- Concentrated in gallbladder: released into small
intestine; bacteria create urobilinogen (brown feces)
18-33
Erythrocyte Death and Disposal
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Amino acids
Iron
Folic acid
Vitamin B12
Erythropoiesis in
red bone marrow
Nutrient
absorption
Erythrocytes
circulate for
120 days
Small intestine
Expired erythrocytes
break up in liver and spleen
Cell fragments
phagocytized
Hemoglobin
degraded
Globin
Heme
Biliverdin
Bilirubin
Bile
Feces
Iron
Storage
Reuse
Figure 18.9
Hydrolyzed to free
amino acids
Loss by
menstruation,
injury, etc.
18-34
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Erythrocyte Disorders
• Polycythemia—an excess of RBCs
– Primary polycythemia (polycythemia vera)
• Cancer of erythropoietic cell line in red bone marrow
– RBC count as high as 11 million RBCs/L; hematocrit
80%
– Secondary polycythemia
• From dehydration, emphysema, high altitude, or
physical conditioning
– RBC count up to 8 million RBCs/L
• Dangers of polycythemia
– Increased blood volume, pressure, viscosity
• Can lead to embolism, stroke, or heart failure
18-36
Anemia
• Causes of anemia fall into three categories
– Inadequate erythropoiesis or hemoglobin synthesis
• Kidney failure and insufficient erythropoietin
• Iron-deficiency anemia
• Inadequate vitamin B12 from poor nutrition or lack of intrinsic
factor (pernicious anemia)
• Hypoplastic anemia—slowing of erythropoiesis
• Aplastic anemia—complete cessation of erythropoiesis
– Hemorrhagic anemias from bleeding
– Hemolytic anemias from RBC destruction
18-37
Anemia
• Anemia has three potential consequences
– Tissue hypoxia and necrosis
• Patient is lethargic
• Shortness of breath upon exertion
• Life-threatening necrosis of brain, heart, or kidney
– Blood osmolarity is reduced producing tissue
edema
– Blood viscosity is low
• Heart races and pressure drops
• Cardiac failure may ensue
18-38
Sickle-Cell Disease
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© Meckes/Ottawa/Photo Researchers, Inc.
Figure 18.10
7 µm
• Hereditary hemoglobin defects that
occur mostly among people of
African descent
• Caused by a recessive allele that
modifies the structure of the
hemoglobin molecule (HbS)
– Differs only on the sixth amino
acid of the beta chain (glutamic
acid for Valine)
– HbS does not bind oxygen well
– RBCs become rigid, sticky,
pointed at ends
– Clump together and block small
blood vessels causing intense
pain
– Can lead to kidney or heart failure,
stroke, rheumatism, or paralysis18-39
Blood Types
• Expected Learning Outcomes
– Explain what determines a person’s ABO and Rh blood
types and how this relates to transfusion compatibility.
– Describe the effect of an incompatibility between mother
and fetus in Rh blood type.
– List some blood groups other than ABO and Rh and
explain how they may be useful.
18-40
Blood Types
• Blood types and transfusion compatibility are a
matter of interactions between plasma proteins and
erythrocytes
• Karl Landsteiner discovered blood types A, B, and O
in 1900
– He won a Nobel Prize in 1930
• Blood types are based on interactions between
antigens and antibodies
18-41
Blood Types
• Antigens
– Complex molecules on surface of cell membrane
that are unique to the individual
• Used to distinguish self from foreign matter
• Foreign antigens generate an immune response
• Agglutinogens—antigens on the surface of the
RBC that is the basis for blood typing
18-42
Blood Types
• Antibodies
– Proteins (gamma globulins) secreted by plasma
cells
•
•
•
•
Part of immune response to foreign matter
Bind to antigens and mark them for destruction
Forms antigen–antibody complexes
Agglutinins—antibodies in the plasma that bring
about transfusion mismatch
• Agglutination
– Antibody molecule binding to antigens
– Causes clumping of red blood cells
18-43
Blood Types
• RBC antigens called
agglutinogens
– Called antigen A and B
– Determined by
carbohydrate moieties
found on RBC surface
• Antibodies called
agglutinins
– Found in plasma
– Anti-A and anti-B
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Type O
Type B
leaves
Type A
Type AB
Key
Galactose
Fucose
N-acetylgalactosamine
Figure 18.12
18-44
The ABO Group
• Your ABO blood type is determined by
presence or absence of antigens
(agglutinogens) on RBCs
–
–
–
–
Blood type A person has A antigens
Blood type B person has B antigens
Blood type AB has both A and B antigens
Blood type O person has neither antigen
• Most common: type O
• Rarest: type AB
18-45
ABO Blood Typing
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Type A
Type B
Type AB
Figure 18.14
Type O
18-46
© Claude Revey/Phototake
The ABO Group
• Antibodies (agglutinins); anti-A and anti-B
• Appear 2 to 8 months after birth; maximum
concentration by 10 years of age
– Antibody-A and/or antibody-B (both or none) are
found in plasma
• You do not form antibodies against your antigens
18-47
Agglutination of Erythrocytes
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Antibodies
(agglutinins)
Figure 18.13
18-48
The ABO Group
• Agglutination
– Each antibody can attach to several foreign antigens
on several different RBCs at the same time
• Responsible for mismatched transfusion reaction
– Agglutinated RBCs block small blood vessels,
hemolyze, and release their hemoglobin over the
next few hours or days
– Hb blocks kidney tubules and causes acute renal
failure
18-49
Transfusion Reaction
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Blood from
type A donor
leaves
Type B
(anti-A)
recipient
Donor RBCs
agglutinated by
recipient plasma
Agglutinated RBCs
block small vessels
Figure 18.15
18-50
Charles Drew—Blood-Banking Pioneer
• Charles Drew
– First black person to
pursue advanced degree
in medicine to study
transfusion and blood
banking
– Used plasma rather than
whole blood; caused less
transfusion reactions
Figure 18.16
18-51
The ABO Group
• Universal donor
– Type O: most common blood type
– Lacks RBC antigens
– Donor’s plasma may have both antibodies
against recipient’s RBCs (anti-A and anti-B)
• May give packed cells (minimal plasma)
• Universal recipient
– Type AB: rarest blood type
– Lacks plasma antibodies; no anti-A or anti-B
18-52
The Rh Group
• Rh (C, D, E) agglutinogens discovered in rhesus
monkey in 1940
– Rh D is the most reactive and a patient is considered
blood type Rh+ if having D antigen (agglutinogens) on
RBCs
– Rh frequencies vary among ethnic groups
• Anti-D agglutinins not normally present
– Form in Rh- individuals exposed to Rh+ blood
• Rh- woman with an Rh+ fetus or transfusion of Rh+ blood
• No problems with first transfusion or pregnancy
18-53
The Rh Group
• Occurs if Rh- mother has formed antibodies
and is pregnant with second Rh+ child
– Anti-D antibodies can cross placenta
• Prevention
– RhoGAM given to pregnant Rh- women
• Binds fetal agglutinogens in her blood so she
will not form anti-D antibodies
18-54
Hemolytic Disease of the Newborn
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
leaves
Rh- mother
Rh
antigen
Second
Rh+ fetus
Rh+ fetus
Uterus
Amniotic sac
and chorion
Anti-D
antibody
Placenta
Figure 18.16
(a) First pregnancy
(b) Between pregnancies
(c) Second pregnancy
• Rh antibodies attack fetal blood causing severe
anemia and toxic brain syndrome
18-55
Leukocytes
• Expected Learning Outcomes
– Explain the function of leukocytes in general and the
individual role of each leukocyte type.
– Describe the appearance and relative abundance of
each type of leukocyte.
– Describe the formation and life history of leukocytes.
– Discuss the types, causes, and effects of leukocyte
excesses and deficiencies.
18-56
Form and Function
• Least abundant formed element
» 5,000 to 10,000 WBCs/L
• Protect against infectious microorganisms and other
pathogens
• Conspicuous nucleus
• Spend only a few hours in the bloodstream before
migrating to connective tissue
• Retain their organelles for protein synthesis
• Granules
– All WBCs have lysosomes called nonspecific (azurophilic)
granules: inconspicuous so cytoplasm looks clear
– Granulocytes have specific granules that contain enzymes
and other chemicals employed in defense against pathogens
18-57
Types of Leukocytes
• Granulocytes
– Neutrophils (60% to 70%): polymorphonuclear leukocytes
• Barely visible granules in cytoplasm; three- to five-lobed nucleus
– Eosinophils (2% to 4%)
• Large rosy-orange granules; bilobed nucleus
– Basophils (less than 1%)
• Large, abundant, violet granules (obscure a large S-shaped
nucleus)
• Agranulocytes
– Lymphocytes (25% to 33%)
• Variable amounts of bluish cytoplasm (scanty to abundant);
ovoid/round, uniform dark violet nucleus
– Monocytes (3% to 8%)
• Largest WBC; ovoid, kidney-, or horseshoe-shaped nucleus
18-58
Granulocytes
• Neutrophils—increased numbers in bacterial infections
– Phagocytosis of bacteria
– Release antimicrobial chemicals
• Eosinophils—increased numbers in parasitic infections,
collagen diseases, allergies, diseases of spleen and CNS
– Phagocytosis of antigen–antibody complexes,
allergens, and inflammatory chemicals
– Release enzymes to destroy large parasites
• Basophils—increased numbers in chickenpox, sinusitis,
diabetes
– Secrete histamine (vasodilator): speeds flow of blood to an injured
area
– Secrete heparin (anticoagulant): promotes the mobility of other
WBCs in the area
18-59
Granulocytes
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Neutrophils
10 µm
Eosinophil
10 µm
Basophil
10 µm
all: © Ed Reschke
Figures in Table 18.6
18-60
Agranulocytes
• Lymphocytes—increased numbers in diverse
infections and immune responses
– Destroy cells (cancer, foreign, and virally infected
cells)
– “Present” antigens to activate other immune cells
– Coordinate actions of other immune cells
– Secrete antibodies and provide immune memory
18-61
Agranulocytes
• Monocytes—increased numbers in viral
infections and inflammation
– Leave bloodstream and transform into macrophages
• Phagocytize pathogens and debris
• “Present” antigens to activate other immune cells—
antigen-presenting cells (APCs)
18-62
Agranulocytes
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Lymphocyte
10 µm
Monocyte
10 µm
both: Michael Ross/Photo Researchers, Inc.
Figures in Table 18.6
18-63
The Leukocyte Life Cycle
• Leukopoiesis—production of white blood cells
– Pluripotent stem cells (PPSCs)
• Myeloblasts—form neutrophils, eosinophils,
basophils
• Monoblasts—form monocytes
• Lymphoblasts give rise to all forms of lymphocytes
– T lymphocytes complete development in thymus
• Red bone marrow stores and releases
granulocytes and monocytes
18-64
The Leukocyte Life Cycle
• Circulating WBCs do not stay in bloodstream
– Granulocytes leave in 8 hours and live 5 days longer
– Monocytes leave in 20 hours, transform into
macrophages, and live for several years
– Lymphocytes provide long-term immunity (decades),
being continuously recycled from blood to tissue fluid
to lymph and back to the blood
18-65
Leukopoiesis
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Pluripotent
stem cell
Colony-forming
units (CFUs)
Mature
cells
Precursor
cells
leaves
Eosinophilic
CFU
Eosinophilic
myeloblast
Eosinophilic
promyelocyte
Eosinophilic
myelocyte
Eosinophil
Basophilic
CFU
Basophilic
myeloblast
Basophilic
promyelocyte
Basophilic
myelocyte
Basophil
Neutrophilic
CFU
Neutrophilic
myeloblast
Neutrophilic
promyelocyte
Neutrophilic
myelocyte
Neutrophil
Monocytic
CFU
Monoblast
Promonocyte
Monocyte
B lymphocyte
B prolymphocyte
Lymphocytic
CFU
T prolymphocyte
T lymphocyte
NK prolymphocyte
NK cell
Figure 18.18
Lymphoblast
18-66
Leukocyte Disorders
• Leukopenia—low WBC count: below 5,000
WBCs/L
– Causes: radiation, poisons, infectious disease
– Effects: elevated risk of infection
• Leukocytosis—high WBC count: above 10,000
WBCs/L
– Causes: infection, allergy, disease
– Differential WBC count: identifies what percentage
of the total WBC count consist of each type of
leukocyte
18-67
Leukocyte Disorders
• Leukemia—cancer of hemopoietic tissue that usually
produces an extraordinary high number of circulating
leukocytes and their precursors
– Myeloid leukemia: uncontrolled granulocyte production
– Lymphoid leukemia: uncontrolled lymphocyte or
monocyte production
18-68
Leukocyte Disorders
Cont.
– Acute leukemia: appears suddenly, progresses rapidly,
death within months
– Chronic leukemia: undetected for months, survival
time 3 years
– Effects: normal cell percentages disrupted; impaired
clotting; opportunistic infections
18-69
The Complete Blood Count
• Hematocrit
• Hemoglobin concentration
• Total count for RBCs, reticulocytes, WBCs,
and platelets
• Differential WBC count
• RBC size and hemoglobin concentration per
RBC
18-70
Normal and Leukemic Blood
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Platelets
Monocyte
Neutrophils
Lymphocyte
Erythrocytes
(a)
Figure 18.19a,b
(b)
75 µm
© Ed Reschke
18-71
Platelets and Hemostasis—
The Control of Bleeding
• Expected Learning Outcomes
– Describe the body’s mechanism for controlling
bleeding.
– List the functions of platelets.
– Describe two reaction pathways that produce blood
clots.
– Explain what happens to blood clots when they are no
longer needed.
– Explain what keeps blood from clotting in the absence
of injury.
– Describe some disorders of blood clotting.
18-72
Platelets and Hemostasis—
The Control of Bleeding
• Hemostasis—the cessation of bleeding
– Stopping potentially fatal leaks
– Hemorrhage: excessive bleeding
• Three hemostatic mechanisms
– Vascular spasm
– Platelet plug formation
– Blood clotting (coagulation)
• Platelets play an important role in all three
18-73
Platelet Form and Function
• Platelets—small fragments of
megakaryocyte cells
– 2 to 4 m diameter; contain “granules”
– Complex internal structure and open
canalicular system
– Amoeboid movement and phagocytosis
• Normal platelet count—130,000 to 400,000
platelets/L
18-74
Platelet Form and Function
• Functions
– Secrete vasoconstrictors that help reduce blood loss
– Stick together to form platelet plugs to seal small
breaks
– Secrete procoagulants or clotting factors to promote
clotting
18-75
Platelet Form and Function
Cont.
– Initiate formation of clot-dissolving enzyme
– Chemically attract neutrophils and monocytes to sites
of inflammation
– Phagocytize and destroy bacteria
– Secrete growth factors that stimulate mitosis to
repair blood vessels
18-76
Platelets
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Pseudopod
Granules
Open
canalicular
system
Mitochondria
(a)
2 µm
Platelets
Bloodflow
Figure 18.20a,b
Endothelium
Sinusoid of
bone marrow
Proplatelets
RBC
WBC
Megakaryocyte
(b)
18-77
a: NIBSC/Science Photo Library/Photo Researchers, Inc.
Platelet Production
• Thrombopoiesis
– Stem cells (that develop receptors for thrombopoietin)
become megakaryoblasts
• Megakaryoblasts
– Repeatedly replicate DNA without dividing
– Form gigantic cells called megakaryocytes with a
multilobed nucleus
• 100 m in diameter, remains in bone marrow
• Megakaryocytes—live in bone marrow adjacent to
blood sinusoids
– Long tendrils of cytoplasm (proplatelets) protrude into
the blood sinusoids: blood flow splits off fragments called
platelets
– Circulate freely for 10 days
– 40% are stored in spleen
18-78
Hemostasis
• Vascular spasm—prompt constriction of a broken
vessel
– Most immediate protection against blood loss
• Causes
– Pain receptors
• Some directly innervate blood vessels to constrict
– Smooth muscle injury
– Platelets release serotonin (vasoconstrictor)
• Effects
– Prompt constriction of a broken vessel
• Pain receptors—short duration (minutes)
• Smooth muscle injury—longer duration
– Provides time for other two clotting pathways
18-79
Hemostasis
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Vasoconstriction
Platelet
plug
Blood
clot
Platelet
Vessel
injury
Collagen
fibers
Endothelial
cells
(a) Vascular spasm
(b) Platelet plug formation
(c) Coagulation
Figure 18.21a–c
All three pathways involve platelets
18-80
Hemostasis
• Endothelium smooth, coated with prostacyclin—a
platelet repellant
• Platelet plug formation
– Broken vessel exposes collagen
– Platelet pseudopods stick to damaged vessel and other
platelets; pseudopods contract and draw walls of vessel
together forming a platelet plug
18-81
Hemostasis
Cont.
– Platelets degranulate releasing a variety of substances
• Serotonin is a vasoconstrictor
• ADP attracts and degranulates more platelets
• Thromboxane A2, an eicosanoid, promotes platelet
aggregation, degranulation, and vasoconstriction
– Positive feedback cycle is active until break in small
vessel is sealed
18-82
Hemostasis
• Coagulation (clotting)—last and most effective defense against
bleeding
– Conversion of plasma protein fibrinogen into insoluble fibrin
threads to form framework of clot
• Procoagulants (clotting factors)—usually produced by the
liver; are present in plasma
– Activate one factor and it will activate the next to form a reaction
cascade
• Extrinsic pathway
– Factors released by damaged tissues begin cascade
• Intrinsic pathway
– Factors found in blood begin cascade (platelet degranulation)
18-83
SEM of Blood Clot
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Figure 18.22
© P. Motta/SPL/Photo Researchers, Inc.
18-84
Coagulation
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Extrinsic mechanism
• Extrinsic pathway
Intrinsic mechanism
Factor XII
Factor XI
(active)
Damaged
perivascular
tissues
Factor IX
(active)
Thromboplastin
(factor III)
Platelets
Inactive
Inactive
Ca2+, PF3
Factor VII
Factor VIII
(active)
Inactive
– Initiated by release of
tissue thromboplastin
(factor III) from damaged
tissue
– Cascade to factor VII, V,
and X (fewer steps)
Ca2+
• Intrinsic pathway
Factor X
(active)
– Initiated by platelets
releasing Hageman factor
(factor XII)
– Cascade to factor XI to IX
to VIII to X
Inactive
Factor III
Factor V
Ca2+
PF3
Prothrombin
activator
Factor V
Prothrombin
(factor II)
Thrombin
Factor XIII
Ca2+
Fibrinogen
(factor I)
Fibrin
Figure 18.23
Fibrin
polymer
• Calcium required for
either pathway
18-85
Reaction Cascade in Clotting
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Factor
XII
Figure 18.24
Factor
IX
Factor
VIII
Factor
X
Prothrombin
activator
Reaction cascade (time)
Factor
XI
Thrombin
Fibrin
• Rapid clotting—each activated cofactor activates many
more molecules in next step of sequence
18-86
Completion of Coagulation
• Activation of factor X
– Leads to production of prothrombin activator
• Prothrombin activator
– Converts prothrombin to thrombin
• Thrombin
– Converts fibrinogen into fibrin
• Positive feedback—thrombin speeds up
formation of prothrombin activator
18-87
The Fate of Blood Clots
• Clot retraction occurs within 30 minutes
• Platelet-derived growth factor secreted by
platelets and endothelial cells
– Mitotic stimulant for fibroblasts and smooth muscle to
multiply and repair damaged vessel
• Fibrinolysis—dissolution of a clot
– Factor XII speeds up formation of kallikrein enzyme
– Kallikrein converts plasminogen into plasmin, a fibrindissolving enzyme that breaks up the clot
18-88
Blood Clot Dissolution
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Prekallikrein
Factor
XII
Kallikrein
Plasminogen
Positive
feedback
loop
Figure 18.25
Plasmin
Fibrin
polymer
Clot dissolution
Fibrin degradation
products
• Positive feedback occurs
• Plasmin promotes formation of fibrin
18-89
Prevention of Inappropriate Clotting
• Platelet repulsion
– Platelets do not adhere to prostacyclin-coated
endothelium
• Thrombin dilution
– By rapidly flowing blood
• Heart slowing in shock can result in clot formation
• Natural anticoagulants
– Heparin (from basophils and mast cells) interferes with
formation of prothrombin activator
– Antithrombin (from liver) deactivates thrombin before
it can act on fibrinogen
18-90
Clotting Disorders
• Deficiency of any clotting factor can shut down the
coagulation cascade
• Hemophilia—family of hereditary diseases
characterized by deficiencies of one factor or another
• Sex-linked recessive (on X chromosome)
– Hemophilia A missing factor VIII (83% of cases)
– Hemophilia B missing factor IX (15% of cases)
• Hemophilia C missing factor XI (autosomal)
18-91
Clotting Disorders
• Physical exertion causes bleeding and
excruciating pain
– Transfusion of plasma or purified clotting
factors
– Factor VIII produced by transgenic bacteria
• Hematomas—masses of clotted blood in the
tissues
18-92
Clotting Disorders
• Thrombosis—abnormal clotting in unbroken vessel
– Thrombus: clot
• Most likely to occur in leg veins of inactive people
– Pulmonary embolism: clot may break free, travel
from veins to lungs
• Embolus—anything that can travel in the blood and
block blood vessels
• Infarction (tissue death) may occur if clot blocks
blood supply to an organ (MI or stroke)
– 650,000 Americans die annually of thromboembolism
(traveling blood clots)
18-93
Clinical Management of Blood Clotting
• Goal—prevent formation of clots or dissolve existing
clots
• Preventing clots
– Vitamin K is required for formation of clotting factors
• Coumarin, warfarin (Coumadin)—vitamin K
antagonists
– Aspirin suppresses thromboxane A2
– Other anticoagulants discovered in animal research
• Medicinal leeches used since 1884 (hirudin)
• Snake venom from vipers (arvin)
18-94
Clinical Management of Blood Clotting
• Dissolving clots that have already formed
– Streptokinase: enzyme made by streptococci bacteria
• Used to dissolve clots in coronary vessels
• Digests almost any protein
– Tissue plasminogen activator (TPA): works faster, is
more specific, and now made by transgenic bacteria
– Hementin: produced by giant Amazon leech
18-95