Chapter 21
*Lecture Outline
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Chapter 21 Outline
• General Composition and Functions of
Blood
• Blood Plasma
• Formed Elements in the Blood
• Hemopoiesis: Production of Formed
Elements
Introduction
Blood serves many functions. Some examples are:
• Transportation of oxygen and carbon dioxide as
well as nutrients and waste products
• Regulation of body temperature, pH, and fluid
volume
• Protection by mounting an immune response
and the production of antibodies
Composition of Blood
Figure 21.1
Composition of Blood
Upon separation by centrifugation, blood
has three factions:
1. Erythrocytes—represent ~ 44% of total
blood volume
2. Buffy coat—represents about 1% of total
blood volume
3. Plasma—represents ~ 55% of total blood
volume
Composition of Blood
Figure 21.2
Blood Smear
Figure 21.3
Blood Plasma
Formed Elements
• The hematocrit is the % of the volume of
all formed elements in one’s blood
• It varies in females from 38%–46% and
between 42%–56% in males
Erythrocytes
• Also referred to as red blood cells or
RBCs, but this is a misnomer as mature
RBCs lack nuclei and other organelles
Figure 21.4
Erythrocytes
• Relatively small (7.5 μm in diameter)
• Unique biconcave shape
• As they pass through small blood vessels,
they line up in single file termed a rouleau
Hemoglobin in Erythrocytes
•
•
•
Every erythrocyte contains 280 million
molecules of a red-pigmented protein called
hemoglobin
Hemoglobin is capable of reversibly
transporting oxygen and carbon dioxide in the
blood
Hemoglobin consists of four globin protein
molecules:
1.
2.
Two alpha (α) chains
Two beta (ß) chains
Molecular Structure of Hemoglobin
Figure 21.5
Hemoglobin
• Each of the four globins possesses a
nonprotein heme group containing an iron
(Fe2+) molecule.
• Each hemoglobin molecule can bind a
combination of four oxygen/carbon dioxide
molecules.
Recycling the Components of Aged
or Damaged Erythrocytes
Figure 21.6
Blood Type
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ABO Blood Types
Antigen A
Antigen B
Antigens A and B
Neither antigen
A nor B
Erythrocytes
Anti-B antibodies
Anti-A antibodies
Neither anti-A nor
anti-B antibodies
Both anti-A and
anti-B antibodies
Plasma
Blood type
Type A
Erythrocytes with
type A surface
antigens and plasma
with anti-B antibodies
Type B
Erythrocytes with
type B surface
antigens and plasma
with anti-A antibodies
(a)
Rh Blood Types
Antigen D
No antigen D
Erythrocytes
No anti-D antibodies
Anti-D antibodies
(after prior exposure)
Rh positive
Erythrocytes with
type D surface
antigens and plasma
with no anti-D
antibodies
Rh negative
Erythrocytes with no
type D surface
antigens and plasma
with anti-D antibodies,
only if there has been
prior exposure to Rh
positive blood
Plasma
Blood type
Figure 21.7
(b)
Type AB
Erythrocytes with
both type A and
type B surface
antigens, and plasma
with neither anti-A
nor anti-B antibodies
Type O
Erythrocytes with
neither type A nor
type B surface
antigens, but plasma
with both anti-A and
anti-B antibodies
Agglutination Reaction
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+
Donor blood type
=
Recipient blood type
Agglutination reaction
Antigen A
+
Type A blood of donor
(has surface antigenA)
=
Type A blood of recipient
(contains anti-B antibodies)
Antigen and
antibody
do not match
No clumping seen.
Successful blood type match.
No agglutination
Antigen A
+
Type A blood of donor
(has surface antigenA)
=
Type B blood of recipient
(contains anti-A antibodies)
Antigen and
antibody match
and connect
Agglutination
Clumping seen.
Hemolysis occurs.
Unsuccessful blood type match.
(a) Agglutination test
Type B recipient erythrocyte
Blood from type A donor
Anti-A antibody in recipient plasma
Type A donor erythrocyte
Agglutinated erythrocytes
from type A donor block
small vessels
Figure 21.8
(b) Erythrocyte agglutination
a: © Jean Claude Revy-ISM/Phototake
Leukocytes
• Unlike erythrocytes, leukocytes possess a
nucleus and organelles.
• They help initiate an immune response and
defend the body against pathogens.
• They are 1.5 to 3 times larger than erythrocytes.
• They are capable of leaving the blood vessels,
diapedesis, and entering a tissue.
• Leukocytes are attracted to a site of infection by
molecules from damaged cells or invading
pathogens. This attraction is called chemotaxis.
Classification of Leukocytes
• The five types of leukocytes are divided
into two classes (granulocytes and
agranulocytes) based on the presence or
absence of visible organelles termed
granules.
Leukocytes
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Table 21.3
Leukocytes
LM 1600x
Eosinophil
LM 1600x
LM 1600x
Neutrophil
Basophil
Granulocytes
Agranulocytes
LM 1600x
LM 1600x
Lymphocyte
Type
GRANULOCYTES
Monocyte
Characteristics
Functions
Approximate %
Neutrophils
Nucleus is multilobed (as many as five lobes)
Cytoplasm contains neutral or pale, distinct
granules (when stained)
Phagocytize pathogens, especially bacteria
Release enzymes that target pathogens
50–70% of total leukocytes
Eosinophils
Nucleus is bilobed
Phagocytize antigen-antibody complexes and
allergens
1–4% of total leukocytes
Cytoplasm contains reddish or pink-orange
granules (when stained)
Basophils
Nucleus is bilobed
Cytoplasm contains deep blue-violet granules
(when stained)
Release chemical mediators to destroy parasitic
worms
Release histamine (vasodilator) and heparin
(anticoagulant) during inflammatory or allergic
reactions
0.5–1% of total leukocytes
AGRANULOCYTES
Lymphocytes
Round or slightly indented nucleus (fills the
cell in smaller lymphocytes)
Nucleus is usually darkly stained
Thin rim of cytoplasm surrounds nucleus
Attack pathogens and abnormal/infected cells
Coordinate immune cell activity
Produce antibodies
20–40% of total leukocytes
Monocytes
Kidney-shaped or C-shaped nucleus
Nucleus is generally pale staining
Abundant cytoplasm around nucleus
Can exit blood vessels and become
macrophages Phagocytize pathogens,
cellular debris, dead cells
2–8% of total leukocytes
Platelets
• Irregular membrane-enclosed cellular fragments
that represent shed cytoplasm from cells in the
red bone marrow called megakaryocytes
• Megakaryocytes are about 15× larger than
erythrocytes
• Platelets are about ¼ the size of erythrocytes
• Platelets are involved in the clotting of blood
Platelets and Megakaryocytes
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Red bone
marrow
Megakaryocyte
Megakaryocytes
LM 1600x
Endothelial cells
(a)
(b)
a: © The McGraw-Hill Companies, Inc./Photo by Dr. Alvin Telser
Figure 21.9
Proplatelets
Platelets
Blood Clot
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Fibrin
Platelets
Erythrocytes
SEM 4100x
Reprinted by permission from Macmillan Publishers Ltd: Nature, Dr. John W. Weisel and Yuri Veklich. Vol. 413, Issue 4, Cover
Image, October 2001. © 2001 Nature Publishing Group
Figure 21.10
Hemopoiesis
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Hemocytoblast
(blood stem cell)
Lymphoid line
Myeloid line
Myeloid stem cell
Multi-CSF
Lymphoid stem cell
Multi-CSF
Multi-CSF
Erythropoiesis
Progenitor cell
Thrombopoiesis
Leukopoiesis
Progenitor cell
B-lymphoblast
GM-CSF
T-lymphoblast
Progenitor cell
Proerythroblast
Megakaryoblast
Myeloblast
M-CSF
Monoblast
EPO
Early erythroblast
Thrombopoietin
G-CSF
Promegakaryocyte
Promyelocytes
Late
erythroblast
M-CSF
Promonocyte
Thrombopoietin
Normoblast
Megakaryocyte
Eosinophilic
myelocyte
Basophilic
myelocyte
Neutrophilic
myelocyte
Eosinophil
Basophil
Neutrophil
Nucleus
ejected
Reticulocyte
Erythrocyte
Thrombopoietin
Platelets
Figure 21.11
Monocyte
B-lymphocyte
T-lymphocyte
Erythropoiesis
• Erythropoiesis is the process of
erythrocyte production.
• About 3 million erythrocytes are produced
per second.
• During maturation all organelles within the
erythrocyte, including the nucleus,
degenerate leaving the erythrocyte with
nothing more than a “bag of hemoglobin.”