Blood is the "river of life" that surges within us. It transports everything that must be carried from one place to another within the body-nutrients, wastes (headed for elimination from the body), and body heat-through blood vessels. For centuries, long before modern medicine, people recognized that blood was vital (some believed "magical"), and its loss was always considered to be a possible cause of death. In this chapter, we consider the composition and function of this life-sustaining fluid. The means by which it is propelled throughout the body is discussed in Chapter 11.
Objective Checklist

Composition and Functions of Blood

• Indicate the composition and volume of whole blood.
• Describe the composition of plasma and discuss its importance in the body.
• List the cell types making up the formed elements and describe the major functions of each type.
• Define anemia, polycythemia, leucopenia, and leukocytosis, and list possible causes for each condition.
• Explain the role of the hemocytoblast.

Hemostasis

• Describe the blood-clotting process.
• Name some factors that may inhibit or enhance the blood-clotting process.

Blood Groups and Transfusions

• Describe the ABO and Rh blood groups.
• Explain the basis for a transfusion reaction.

Developmental Aspects of Blood

• Explain the basis of physiologic jaundice seen in some newborn babies.
• Indicate blood disorders that increase in frequency in the aged.