Introduction to Blood

Learning Objectives

  1. Describe the basic functions, physical characteristics, and components of blood.
  2. Describe the appearance, constituents and functions of plasma.
  3. Describe the functions, structural features, production and destruction of
    erythrocytes. Include the roles of hemoglobin and erythropoietin in your
    discussion.
  4. Describe the production, basic functions and properties of each of the five main
    varieties of leukocytes.
  5. Describe the structural appearance and basic function of platelets.
  6. Describe the three stages of hemostasis.
  7. Describe the process of fibrinolysis.
This photo shows a red blood cell and a white blood cell.

Figure 1. Blood cell types.

Single-celled organisms do not need blood. They obtain nutrients directly from and excrete wastes directly into their environment. The human organism cannot do that. Our large, complex bodies need blood to deliver nutrients to and remove wastes from our trillions of cells. The heart pumps blood throughout the body in a network of blood vessels. Together, these three components—blood, heart, and vessels—make up the cardiovascular system. This chapter focuses on the medium of transport: blood.

A single drop of blood contains millions of red blood cells, white blood cells, and platelets. One of each type is shown in Figure 1, isolated from a scanning electron micrograph.