000200010270575674_R1_CH17_p0634-0660.qxd

14/2/2011 06:06 PM Page 634

17 Overview: Blood Composition and Functions (pp. 635–636) Components (p. 635) Physical Characteristics and Volume (p. 635) Functions (pp. 635–636)

Blood Plasma (p. 636) Formed Elements (pp. 637–649) Erythrocytes (pp. 637–643) Leukocytes (pp. 643–648) Platelets (pp. 648–649)

Hemostasis (pp. 649–654)

Blood

Vascular Spasm (p. 649) Platelet Plug Formation (pp. 649–650) Coagulation (pp. 650–652) Clot Retraction and Repair (p. 652) Fibrinolysis (p. 652) Factors Limiting Clot Growth or Formation (pp. 652–653) Disorders of Hemostasis (pp. 653–654)

Transfusion and Blood Replacement (pp. 654–657) Transfusion of Red Blood Cells (pp. 654–656) Restoring Blood Volume (pp. 656–657)

Diagnostic Blood Tests (p. 657) Developmental Aspects of Blood (p. 657)

634

B

lood is the river of life that surges within us, transporting nearly everything that must be carried from one place to another. Long before modern medicine, blood was viewed as magical—an elixir that held the mystical force of life—because when it drained from the body, life departed as well. Today, centuries later, blood still has enormous importance in the practice of medicine. Clinicians examine it more often than any other tissue when trying to determine the cause of disease in their patients. In this chapter, we describe the composition and functions of this life-sustaining fluid that serves as a transport “vehicle” for the organs of the cardiovascular system. To get started, we need a brief overview of blood circulation, which is initiated by the pumping action of the heart. Blood exits the heart via arteries, which branch repeatedly until they

000200010270575674_R1_CH17_p0634-0660.qxd

14/2/2011 06:06 PM Page 635

Chapter 17 Blood

1 Withdraw blood and place in tube.

Plasma • 55% of whole blood • Least dense component Buffy coat • Leukocytes and platelets •