Lymphatic System and Immunity

Lymphatic System and Immunity

After studying this chapter, the reader should be able to

1. Define immunity and explain its relationship to the lymphatic system.

2. Identify the major components of the lymphatic system.

3. Describe the structure of lymphoid tissues, vessels, and organs.

4. Describe the major functions of the lymphatic system.

5. Describe a lymph node and its functions.

6. Explain the difference between nonspecific and specific defenses.

7. Explain the role of lymphocytes in the immune response.

8. Explain the roles of the thymus and spleen.

9. Identify the body’s three lines of defense against pathogens.

10. Distinguish between humoral and cellular immunity.

Overview

Similarly to the cardiovascular system, the lymphaticsystem transports fluids through a network of vessels. The primary functions of the lymphatic system are the production, maintenance, and distribution of lymphocytes. Another major function is to trans-port excess fluid out of interstitial spaces in tissues and return it to the bloodstream (FIGURE 20-1), which may be up to 3 liters of fluid per day. Without the lymphatic system, fluid would accumulate in tis-sue spaces. The production of lymphocytes is called lymphopoiesis.

The biochemicals and cells of the lymphatic sys-tem attack “foreign” particles in the body, allowing the destruction of infectious microorganisms and viruses, toxins, and cancer cells. Many organs and body systems work together to maintain life and proper health. The lymphatic system is vital in this capacity, ­responsible for defending the body against environmental hazards,­ such as various pathogens, and ­internal threats, such as cancer cells. The lymphatic system is the structural basis of our immune system. Lymphoid organs and tissues contain lymphocytes and phagocytic cells. Together, these play essential roles in how the body defends itself and resists disease.