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CHAPTER
17
Blood
Objectives
Overview: Blood Composition and Functions
1. Describe the composition and physical characteristics of whole blood. Explain why it is
Blood Plasma
3. Discuss the composition and functions of plasma.
Formed Elements
4. Describe the structure, function, and production of erythrocytes.
5. Describe the chemical composition of hemoglobin.
Hemostasis
11. Describe the process of hemostasis. List factors that limit clot formation and prevent
undesirable clotting.
12. Give examples of hemostatic disorders. Indicate the cause of each condition.
Transfusion and Blood Replacement
Diagnostic Blood Tests
15. Explain the diagnostic importance of blood testing.
Developmental Aspects of Blood
Suggested Lecture Outline
I. Overview: Blood Composition and Functions (pp. 632–633; Fig. 17.1)
A. Components (p. 632; Fig. 17.1)
2. Blood that has been centrifuged separates into three layers: erythrocytes, the buffy
coat, and plasma.
1. Blood is a slightly basic (pH = 7.35–7.45) fluid that has a higher density and viscosity
than water, due to the presence of formed elements.
1. Blood is the medium for delivery of oxygen and nutrients, removal of metabolic
wastes to elimination sites, and distribution of hormones.
3. Blood protects against excessive blood loss through the clotting mechanism and from
infection through the immune system.
II. Blood Plasma (p. 633; Table 17.1)
A. Blood plasma consists of mostly water (90%) and solutes including nutrients, gases,
hormones, wastes, products of cell activity, ions, and proteins (p. 633; Table 17.1).
B. Plasma proteins account for 8% of plasma solutes (p. 633).
1. Albumin constitutes roughly 60% of plasma proteins and functions as a carrier, a
pH buffer, and an osmoregulating protein.
III. Formed Elements (pp. 634–646; Figs. 17.2–17.12; Table 17.2)
A. Erythrocytes (Red Blood Cells) (pp. 634–640; Figs. 17.2–17.8; Table 17.2)
1. Erythrocytes, or red blood cells, are small cells that are biconcave in shape, lack nuclei
and most organelles, and contain mostly hemoglobin.
2. Erythrocytes function to transport respiratory gases in the blood on hemoglobin.
a. The normal range for hemoglobin in the blood is 13–18 g/100 ml.
3. Hemoglobin is a protein consisting of four polypeptide chains, globin proteins, each
with a ringlike heme.
4. Production of Erythrocytes
a. Hematopoiesis, or blood cell formation, occurs in the red bone marrow.
b. All blood cells form from a common hematopoietic stem cell, the hemocytoblast.
5. Erythrocyte production is controlled by the hormone erythropoietin (EPO), produced
mostly by the kidneys when certain kidney cells become hypoxic.
a. Erythropoietin production is triggered by excessive loss of RBCs or reduced
availability of oxygen.
6. Dietary requirements for erythrocyte formation include iron, vitamin B12, and folic
acid, as well as proteins, lipids, and carbohydrates.
9. Erythrocyte Disorders
a. Anemias are characterized by a deficiency in RBCs that may originate from several
causes:
i. Hemorrhagic anemia resulting from excessive blood loss.
ii. Iron-deficiency, pernicious, or renal anemia resulting from nutritional
deficiency in either iron or vitamin B12, or a lack of EPO, which leads to under-
production of erythrocytes.
B. Leukocytes (White Blood Cells) (pp. 640–645; Figs. 17.9–17.12; Table 17.2)
1. Leukocytes, or white blood cells, are the only formed elements that are complete cells
and make up less than 1% of total blood volume.
2. Leukocytes are critical to our defense against disease, and can leave the blood to enter
the tissues, a process called diapedesis, and move through the tissue by amoeboid
movement.
3. Granulocytes are a main group of leukocytes characterized as large cells with lobed
nuclei and visibly staining granules; all are phagocytic.
4. Agranulocytes are lymphocytes and monocytes that lack visibly staining granules.
a. Lymphocytes comprise 25%+ of all WBCs and are found throughout the
body—but relatively few are found in the blood.
5. Production and Life Span of Leukocytes
a. Leukopoiesis, the formation of white blood cells, is regulated by the production of
interleukins and colony-stimulating factors (CSF).
years.
6. Leukocyte Disorders
a. Leukopenia is an abnormally low white blood cell count, possibly due to drugs,
such as glucocorticoids or anticancer drugs.
C. Platelets (pp. 645–646; Fig. 17.12)
1. Platelets are not complete cells, but fragments of large cells called megakaryocytes,
5. Platelets enter the blood when a megakaryoblast sends cytoplasmic extensions through
a sinusoid wall, ruptures, and releases platelets.
IV. Hemostasis (pp. 646–651; Figs. 17.13–17.15; Table 17.3)
A. A break in a blood vessel stimulates hemostasis, a fast, localized response to reduce
blood loss through clotting (p. 646).
2. Once attached, other platelets are attracted to the site of injury, activating a positive
feedback loop for clot formation.
D. Coagulation, or blood clotting, is a multistep process in which blood is transformed from
a liquid to a gel (pp. 647–649; Figs. 17.13–17.15; Table 17.3).
1. Factors that promote clotting are called clotting factors, or procoagulants; those that
inhibit clot formation are called anticoagulants.
4. Thrombin catalyzes the reactions that convert fibrinogen to fibrin, which forms strands
that form the structure of a clot.
E. Clot Retraction and Fibrinolysis (p. 649)
1. Clot retraction is a process in which the contractile proteins within platelets contract
and pull on neighboring fibrin strands, squeezing plasma from the clot and pulling
damaged tissue edges together.
F. Factors Limiting Clot Growth or Formation (p. 649)
1. Two mechanisms limit the size of clots as they form:
a. Rapidly moving blood disseminates clotting factors before they can initiate a
clotting cascade.
G. Disorders of Hemostasis (pp. 650–651)
1. Thromboembolic disorders result from conditions that cause undesirable clotting, such
as roughening of vessel endothelium, slow-flowing blood, or blood stasis.
2. Anticoagulant drugs, such as aspirin, heparin, and warfarin, are used clinically to
prevent undesirable clotting.
3. Bleeding disorders arise from abnormalities that prevent normal clot formation.
a. Thrombocytopenia is a deficiency in circulating platelets and may result from any
4. Disseminated intravascular coagulation is a situation leading to widespread clotting
throughout intact vessels and may occur as a complication of pregnancy, septicemia,
or incompatible blood transfusions.
V. Transfusion and Blood Replacement (pp. 651–653; Fig. 17.16; Table 17.4)
A. Transfusion of whole blood is routine when blood loss is substantial or when treating
thrombocytopenia (p. 651).
1. Humans have different blood types based on specific antigens, called agglutinogens,
on RBC membranes.
2. At least 30 groups of RBC antigens occur in humans, but the ABO and Rh antigens
cause strong transfusion reactions.
a. ABO blood groups are based on the presence or absence of two types of heritable
agglutinogens: type A, and type B.
4. A transfusion reaction occurs if the agglutinogens in the donor blood type are attacked
by the recipient’s blood plasma agglutinins, resulting in agglutination and hemolysis
5. Blood typing involves determination of possible transfusion reactions prior to
transfusion between the donor and recipient blood types.
B. Blood volume expanders are given in cases of extremely low blood volume (p. 653).
1. Isotonic salt solutions, such as Ringer’s solution, mimic the normal electrolyte
concentrations of plasma.
2. Plasma expanders mimic the osmotic properties of albumin in the blood, but actually
provide no benefit over electrolyte solutions.
VI. Diagnostic Blood Tests (pp. 653–654)
A. Changes in some of the visual properties of blood can signal diseases such as anemia,
heart disease, and diabetes (p. 653).
VII. Developmental Aspects of Blood (p. 654)
A. Prior to birth, blood cell formation occurs within the fetal yolk sac, liver, and spleen, but
by the seventh month, red bone marrow is the primary site of hematopoiesis (p. 654).
B. Fetal blood cells form hemoglobin F, which has a higher affinity for oxygen than adult
hemoglobin, hemoglobin A (p. 654).
Cross References
Additional information on topics covered in Chapter 17 can be found in the chapters listed below.
1. Chapter 3: Diffusion; osmosis
2. Chapter 4: Tissue repair
3. Chapter 6: Hematopoietic tissue
4. Chapter 18: Role of the heart in blood delivery
5. Chapter 19: Vasoconstriction as a mechanism of blood flow control; general overview of
arteries, capillaries, and veins
Lecture Hints
1. Emphasize that the hematocrit is an indirect measurement of the O2-carrying capacity of
the blood. More red blood cells mean more O2 carried by the same volume of blood.
3. Spend some time with the feedback loop involved in erythropoiesis. This is a typical
negative feedback mechanism that allows the application of critical thought processes.
6. Emphasize that ABO incompatibility does not require sensitization by a previous blood
transfusion, while Rh incompatibility does.
7. The regulation of hemostasis is often difficult for students. Areas to clarify include: the
8. Students often have difficulty with the concepts of blood antigens and antibodies, and
relating them to the terms agglutinogens and agglutinins. Stress the location of each in
the blood.
Activities/Demonstrations
2. Display equipment used to perform a hematocrit, sedimentation rate, and cell counts.
3. Obtain a synthetic blood typing kit, have students type the blood, and note the
coagulation response.
4. Provide a sample of centrifuged animal blood so that students can examine consistency,
Critical Thinking/Discussion Topics
1. Discuss the procedure of autologous transfusion.
2. Discuss why gamma globulin injections are painful.
3. Why do red blood cells lack a nucleus? Why is this an advantage?
Library Research Topics
1. Research the blood disorders associated with IV street drug use.
2. Investigate inherited blood disorders.
3. Explore the blood antigens other than A, B, and Rh.
List of Figures and Tables
All of the figures in the main text are available in JPEG format, PPT, and labeled & unlabeled
format on the Instructor Resource DVD. All of the figures and tables will also be available in
Transparency Acetate format. For more information, go to www.pearsonhighered.com/educator.
Figure 17.1 The major components of whole blood.
Figure 17.2 Photomicrograph of a human blood smear stained with Wright’s stain.
Figure 17.8 Sickle-cell anemia.
Figure 17.9 Types and relative percentages of leukocytes in normal blood.
Figure 17.10 Leukocytes.
Figure 17.11 Leukocyte formation.
Figure 17.16 Blood typing of ABO blood types.
Table 17.1 Composition of Plasma
Table 17.2 Summary of Formed Elements of the Blood
Table 17.3 Blood Clotting Factors (Procoagulants)
Table 17.4 ABO Blood Groups
Answers to End-of-Chapter Questions
Multiple-Choice and Matching Question answers appear in Appendix H of the main text.
Short Answer Essay Questions
11. a. The formed elements are living blood cells. The major categories of formed elements
are erythrocytes, leukocytes, and platelets.
12. Hemoglobin is made up of the protein globin bound to the pigment heme. Each molecule
contains four polypeptide chains (globins) and four heme groups, each bearing an atom
13. With a high hematocrit, you would expect the hemoglobin determination to be
14. In addition to carbohydrates for energy and amino acids needed for protein synthesis, the
nutrients needed for erythropoiesis are iron and certain B vitamins. (p. 638)
15. a. In the process of erythropoiesis, a hemocytoblast is transformed into a proerythroblast,
which gives rise to basophilic, then polychromatic erythroblasts, orthochromatic
16. The physiological attributes that contribute to the function of white blood cells in the
17. a. With a severe infection, the WBC count would be closest to 15,000 WBC/mm3 of
18. a. Platelets appear as small discoid fragments of large, multinucleated cells called
19. a. Literally, hemostasis is “blood standing still” because it refers to clotted blood. It
encompasses the steps that prevent blood loss from blood vessels. (p. 646)
b. The three major steps of coagulation include the formation of prothrombin activator
20. a. Fibrinolysis is the disposal of clots when healing has occurred.
b. The importance of this process is that without it, blood vessels would gradually
become occluded by clots that are no longer necessary. (p. 649)
21. a. Clot overgrowth is usually prevented by rapid removal of coagulation factors and
22. Bleeding disorders occur when the liver cannot synthesize its usual supply of
procoagulants. (p. 650)
23. a. A transfusion reaction involves agglutination of foreign RBCs, leading to clogging of
small blood vessels, and lysis of the donated RBCs. It occurs when mismatched blood
24. Among other things, poor nutrition can cause iron-deficiency anemia due to inadequate
25. The most common blood-related problems for the aged include chronic types of
leukemias, anemias, and thromboembolic disease. (p. 654)
Critical Thinking and Clinical Application Questions
1. Hematopoiesis is a process involving fairly rapid cell production. Because chemothera-
2. a. The woman would probably be given a whole blood transfusion. It is essential that she
maintain sufficient O2-carrying capacity to serve fetal needs and blood volume to
3. a. Polycythemia accounts for his higher erythrocyte count because of the need to produce
more RBCs to increase his O2 binding and transport ability in the high-altitude (thinner
air) environment of the Alps. Enhanced production of RBCs was prompted by an
increased production of erythropoietin, in response to chronic hypoxia.
4. As a consequence of acute lymphocytic anemia, Janie’s leukocytes are immature or
abnormal and are incapable of defending her body in the usual way. (p. 639)
5. Red bone marrow is the site of hemopoiesis, and if it is destroyed by benzene, hemocy-
toblasts will not be produced, which will reduce the production of megakaryocytes (the
progenitor cells of platelets, which are involved in clotting). (p. 636)
7. Based on the description of the roles of various proteins in the clotting process, the two
blood proteins are thrombin and fibrinogen. (p. 648)
8. An elevated RBC count could be related to smoking, due to the frequent hypoxia that
9. Aspirin is a mild anticoagulant, which could cause excessive bleeding during or after
surgery. (p. 650)
Suggested Readings
Ballerini, David R., Xu Li, and Wei Shen. “An Inexpensive Thread-Based System for Simple
and Rapid Blood Grouping.” Analytical & Bioanalytical Chemistry 399 (5) (Feb. 2011):
1869–1875.
(2012): 321–339.
Gratzer, Walter. “The Wright Stuff.” Nature 416 (6878) (March 2002): 275–277.
Luzzatto, Lucio, and Rosario Notaro. “Haemoglobin’s Chaperone.” Nature 417 (6890)
