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Blood
Chapter 12
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2. Learning Objectives Lesson 12.1: Blood
Describe the primary functions of blood.
Describe the characteristics of blood plasma.
List the formed elements of blood and identify the most important function of each.
Discuss the structure and function of red blood cells and how red blood cell numbers and hemoglobin content may change to produce anemia.
Describe ABO and Rh blood typing.
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3. Learning Objectives Lesson 12.1: Blood (Cont.)
Discuss the structure and function of white blood cells.
Explain the steps involved in blood clotting.
Define the following medical terms associated with blood: acidosis, serum, hematocrit, anemia, sickle cell, polycythemia, erythroblastosis fetalis, Rh factor, leukocytosis, leukopenia, phagocytosis, fibrinogen, thrombosis.
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Blood Composition
Blood tissue
Blood plasma
Definition
Blood minus its cells
Composition
Water containing many dissolved substances (e.g., nutrients, salts, and hormones)
Amount of blood
Varies with size and sex
4 to 6 L about average
About 7% to 9% of body weight
Blood is a fluid tissue with many kinds of chemicals dissolved in it.
Liquid (extracellular part) is called plasma.
Blood not only performs vital pickup and delivery services but also provides much of the protection necessary to withstand foreign “invaders.”
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5. Formed Elements of the Blood
Table 12-1 shows the formed elements of blood – each blood cell and its functions.
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6. Blood Composition (Cont.)
Formed elements (Figure 12-1)
Types
Red blood cells (RBCs), or erythrocytes
White blood cells (WBCs), or leukocytes
Granular leukocytes: Neutrophils, eosinophils, and basophils
Agranular leukocytes: Lymphocytes and monocytes
Platelets, or thrombocytes
Count
RBCs: 4.2 to 6.2 million per mm3 of blood
WBCs: 5000 to 10,000 per mm3 of blood
Platelets: 300,000 per mm3 of blood
There are three main types (RBCs, WBCs, and platelets/thrombocytes) of formed elements.
It is difficult to believe how many blood cells and cell fragments there are in the body. For instance, 5,000,000 RBCs, 7,500 WBCs, and 300,000 platelets in 1 cubic millimeter (mm3) of blood (a tiny fraction of a drop) would be considered normal counts.
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7. Blood Composition (Cont.)
Hematopoiesis
Definition
Formation of new blood cells
Two kinds of connective tissue make blood cells for the body
Myeloid tissue
Lymphoid tissue
The formation of new blood cells is called hematopoiesis.
Red bone marrow (myeloid tissue) forms all blood cells except some lymphocytes and monocytes, which are formed by lymphatic tissue in the lymph nodes, thymus, and spleen.
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8. Components of Blood
Figure 12-1 shows the components of blood, including approximate values for the components of blood in a normal adult.
Courtesy Barbara Cousins.
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Red Blood Cells
RBC structure and function
Structure
Disk-shaped, without nuclei
Function
Transport oxygen and carbon dioxide
Mature RBCs have no nucleus or cytoplasmic organelles.
Because of this they are unable to reproduce themselves or replace lost or damaged cellular components.
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Red Blood Cells (Cont.)
RBC count
Complete blood cell count (CBC)
Battery of tests used to measure amounts or levels of many blood constituents
Hematocrit (Hct) test
Medical test in which a centrifuge is used to separate whole blood into formed elements and liquid fraction (Figure 12-3)
Buffy coat is WBC and platelet fraction
Normal RBC level is about 45%
Erroneous test result can be caused by dehydration
The hematocrit test—also called packed-cell volume (PCV) test—gives an estimate of the proportion of RBCs to whole blood.
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Hematocrit (Hct) Test
Figure 12-3: A, A normal percentage of RBCs. B, Anemia (a low percentage of RBCs). C, Polycythemia (a high percentage of RBCs). D, Photograph shows a laboratory centrifuge used to “spin down” tubes of whole blood to separate the formed elements from the plasma.
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Red Blood Cells (Cont.)
Hemoglobin
Anemia
Inability of blood to carry adequate oxygen to tissues; caused, for example, by:
Inadequate RBC numbers
Deficiency of hemoglobin
Pernicious anemia: Deficiency of vitamin B12
Blood types (Figure 12-6)
Antigen
Substance that can activate immune system
Antibody
Substance made by body in response to stimulation by an antigen
Hemoglobin molecules that fill the millions of RBCs are critical in transport and exchange of oxygen and carbon dioxide between the blood and the body’s cells.
The term anemia describes a number of different disease conditions caused by an inability of the blood to carry sufficient oxygen to the body cells.
Polycythemia is a condition of an abnormally high RBC count.
Blood is often identified as a specific “type” by using the ABO system and Rh system of classification.
Many antibodies react with their antigens to cause clumping; that is, they agglutinate the antigens.
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Red Blood Cells (Cont.)
Blood types: ABO system
Type A
Type A self-antigens in RBCs; anti-B type antibodies in plasma
Type B
Type B self-antigens in RBCs; anti-A type antibodies in plasma
Type AB
Type A and type B self-antigens in RBCs; no anti-A or anti-B antibodies in plasma
Type O
No type A or type B self-antigens in RBCs; both anti-A and anti-B antibodies in plasma
Each person’s blood is one of the blood types in the ABO system of typing.
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14. ABO Blood Typing
Figure 12-6: The left columns shows the recipient’s blood characteristics, and the top row shows the donor’s blood type.
Courtesy Barbara Cousins.
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Red Blood Cells (Cont.)
Blood types: Rh system
Rh-positive blood
Rh factor antigen present in RBCs
Rh-negative blood
No Rh factor present in RBCs; no anti-Rh antibodies present naturally in plasma; anti-Rh antibodies, however, appear in the plasma of Rh-negative persons if Rh-positive RBCs have been introduced into their bodies
Plasma never naturally contains anti-Rh antibodies.
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Red Blood Cells (Cont.)
Blood types: Rh system
Universal donor and universal recipient blood
Type O Rh negative: Universal donor blood
Type AB Rh positive: Universal recipient blood
Hemolytic anemia called erythroblastosis fetalis—may occur when:
Rh-negative mother carries a second fetus
Rh-positive fetus; caused by mother’s Rh antibodies reacting with fetus's Rh-positive cells
Blood types: Combined ABO-Rh system
Both the ABO and Rh systems are often used in combination to identify a person’s blood type
All Rh-negative mothers who carry an Rh-positive baby should be treated with an immunoglobulin (antibody) serum (RhoGAM).
Likewise, a person with Rh-negative blood who receives a transfusion of Rh-positive blood will also develop anti-Rh antibodies and be at risk of an immune reaction if exposed to Rh-positive blood again later.
Knowing one’s blood type can be lifesaving in a medical emergency or during surgery.
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White Blood Cells
Introduction to WBCs
WBCs are also called leukocytes
General function: Defense
WBC count
Differential WBC count reveals proportions of each type of WBC
Leukopenia: Abnormally low WBC count
Leukocytosis: Abnormally high WBC count
Different types of WBCs are categorized by the presence or absence of stained granules in their cytoplasm.
All of the WBCs are involved in immunity.
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18. White Blood Cells (Cont.)
WBC types
Granular leukocytes
Neutrophils and monocytes carry out phagocytosis
Eosinophils protect against parasitic irritants and allergies
Basophils produce heparin, which inhibits clotting
Agranular leukocytes
Lymphocytes produce antibodies (B-lymphocytes) or directly attack foreign cells (T-lymphocytes)
WBC disorders
Leukemia (cancer)
Elevated WBC count
Cells do not function properly
Leukemia is the term used to describe a number of cancers affecting the WBCs.
Different types of leukemia are either “acute” or “chronic.”
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19. Platelets and Blood Clotting
Play an essential role in blood clotting
Blood clotting (Figure 12-10)
Clotting factors released at the injury site produce prothrombin activator
Prothrombin activator and calcium convert prothrombin to thrombin
Thrombin reacts with fibrinogen and triggers formation of fibrin, which traps RBCs to form a clot
Platelets are the third main type of formed element.
Platelets are also called thrombocytes.
Hemostasis is a process of how bleeding stops when an injury occurs.
Abnormal blood clots can occur.
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20. Blood Clotting
Blood clotting is described in the basic steps outlined in Figure B
B: Copyright Dennis Kunkel Microscopy, Inc.
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21. Platelets and Blood Clotting (Cont.)
Abnormal blood clots
Thrombus: When a clot stays in the place it has formed
Condition is called thrombosis
Embolus: When a part of a clot dislodges and circulates through the bloodstream
Condition is called embolism
A number of drugs are now available to help dissolve abnormal clots.
Streptokinase and recombinant tissue plasminogen activator are drugs frequently used in a variety of conditions, including treatment of clot-induced strokes, heart attacks, and other thrombus-induced and embolus-induced medical emergencies.
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Blood Terms
Acidosis
Serum
Hematocrit
Anemia
Sickle cell
Polycythemia
Erythroblastosis fetalis
Acidosis: When the alkalinity of blood decreases toward neutral; increased acidity in the blood.
Serum: Plasma minus its clotting factors such as fibrinogen.
Hematocrit (Hct): A component of the complete blood count (CBC), it provides information about the volume of RBCs in a blood sample.
Anemia: An inability of the blood to carry sufficient oxygen to the body cells.
Sickle cell: A fragile, crescent-shaped red blood cell, caused by a genetic disease (sickle cell anemia) in which abnormal forms of hemoglobin, called sickle hemoglobin, or hemoglobin S (HbS), form crystals and weaken the cell when the blood oxygen level is low.
Polycythemia: A condition in which bone marrow produces an excess of RBCs, such that the blood may become too thick to flow properly, resulting in a stroke or heart attack.
Erythroblastosis fetalis: A type of hemolytic anemia caused by the mother’s Rh antibodies reacting with the baby’s Rh-positive cells.
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Blood Terms
Rh factor
Leukocytosis
Leukopenia
Phagocytosis
Fibrinogen
Thrombosis
Rh factor: A type of protein on the surface of red blood cells.
Leukocytosis: Abnormally high WBC count.
Leukopenia: Abnormally low WBC count.
Phagocytosis: The process by which a cell engulfs a solid particle.
Fibrinogen: A normal plasma protein; aids in the formation of blood clots.
Thrombosis: When a clot stays in the place that it is formed.
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Questions?
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