Page 703 - Fundamentals of anatomy physiology

690 Unit 4 Fluids and Transport

Table 19–1 RBC Tests and Related Terminology

Terms Associated with Abnormal Values

Test Determines Elevated Depressed

Hematocrit (Hct) Percentage of formed elements in whole blood Polycythemia (may reflect Anemia
Reticulocyte count (Retic.) Normal = 37–54% erythrocytosis or leukocytosis) Diminished erythropoiesis
Hemoglobin concentration (Hb; Hgb) Percentage of circulating reticulocytes Reticulocytosis Anemia
RBC count Normal = 0.8% Polycythemia Anemia
Mean corpuscular volume (MCV) Concentration of hemoglobin in blood Erythrocytosis/polycythemia Microcytic
Mean corpuscular hemoglobin Normal = 12–18 g/dL Macrocytic Hypochromic
concentration (MCHC) Number of RBCs per μL of whole blood Hyperchromic
Normal = 4.2–6.3 million cells/μL
Average volume of one RBC
Normal = 82–101 μm3/cell (normocytic)
Average weight of Hb in one RBC
Normal = 27–34 ug/RBC (normochromic)

The tests can also be useful in detecting problems, such as in- cells have at least 50 kinds of surface antigens, but three surface
ternal bleeding, that may not produce other obvious signs or antigens are of particular importance: A, B, and Rh (or D).
symptoms. Table 19–1 lists examples of important blood tests
and related terms. Based on RBC surface antigens, there are four blood types
(Figure 19–6a): Type A blood has surface antigen A only, type B
19 Checkpoint has surface antigen B only, type AB has both A and B, and
type O has neither A nor B. Individuals with these blood types
8. Describe hemoglobin. are not evenly distributed throughout the world. The average
9. How would the hematocrit change after an individual percentages for various populations in the United States are
given in Table 19–2.
suffered a significant blood loss?
10. Dave develops a blockage in his renal arteries that The term Rh positive (Rh+) indicates the presence of the
Rh surface antigen, commonly called the Rh factor. The absence
restricts blood flow to the kidneys. What effect will this of this antigen is indicated as Rh negative (Rh−). When the
have on his hematocrit? complete blood type is recorded, the term Rh is usually omit-
1 1. In what way would a disease that causes damage to the ted, and a positive or negative sign is used. For example, the
liver affect the level of bilirubin in the blood? data are reported as O negative (O–), A positive (A+), and so
on. As in the distribution of A and B surface antigens, Rh type
See the blue Answers tab at the back of the book. differs by ethnic group and by region (Table 19–2).

19-4 The ABO blood types and Rh Your immune system ignores these surface antigens—
called agglutinogens (a-glu. -TIN-o. -jenz)—on your own
system are based on antigen–antibody RBCs. However, your plasma contains antibodies, sometimes
responses called agglutinins (a-GLU-ti-ninz), that will attack the anti-
gens on “foreign” RBCs. When these antibodies attack, the
Learning Outcome Explain the importance of blood typing, and the foreign cells agglutinate, or clump together. This process is
basis for ABO and Rh incompatibilities. called agglutination. If you have type A blood, your plasma
contains anti-B antibodies, which will attack type B surface
Antigens are substances that can trigger a protective defense antigens. If you have type B blood, your plasma contains
mechanism called an immune response. Most antigens are pro- anti-A antibodies. The RBCs of an individual with type O blood
teins, but some other types of organic molecules are antigens have neither A nor B surface antigens, and that person’s
as well. Your plasma membranes contain surface antigens, plasma contains both anti-A and anti-B antibodies. A type AB
substances that your immune system recognizes as “normal.” individual has RBCs with both A and B surface antigens, and
In other words, your immune system ignores these substances the plasma does not contain anti-A or anti-B antibodies. The
rather than attacking them as “foreign.” presence of anti-A and/or anti-B antibodies is genetically
determined. These antibodies are present throughout life,
Your blood type is determined by the presence or absence of regardless of whether the individual has ever been exposed
specific surface antigens in RBC plasma membranes. The surface to foreign RBCs.
antigens involved are integral membrane glycoproteins or glyco-
lipids whose characteristics are genetically determined. Red blood