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Chapter 13 The Lymphatic System and Immunity

THE LYMPHATIC SYSTEM (FIGURE 13-1) Lymph—fluid in the tissue spaces that carries protein molecules and other substances back to the blood Lymphatic vessels—permit only one-way movement of lymph Lymphatic capillaries—tiny blind-ended tubes distributed in tissue spaces (Figure 13-2) Microscopic in size Sheets consisting of one cell layer of simple squamous epithelium Poor “fit” between adjacent cells results in porous walls Called lacteals in the intestinal wall (fat transportation from food to bloodstream) Right lymphatic duct (Figure 13-3) Drains lymph from the right upper extremity and right side of head, neck, and upper torso Thoracic duct Largest lymphatic vessel Has an enlarged pouch along its course, called cisterna chyli Drains lymph from about three-fourths of the body (Figure 13-3)

THE LYMPHATIC SYSTEM Lymph nodes Filter lymph (Figure 13-4) Located in clusters along the pathway of lymphatic vessels (Figures 13-1, 13-5, and 13-6) Functions include defense and WBC formation Flow of lymph: to node via several afferent lymph vessels and drained from node by a single efferent lymph vessel