1. PowerPoint® Lecture Slides prepared by Jason LaPres
C h a p t e r 23
The Lymphoid System
PowerPoint® Lecture Slides prepared by Jason LaPres
North Harris College
Houston, Texas
Copyright © 2009 Pearson Education, Inc.,
publishing as Pearson Benjamin Cummings

2. Introduction The lymphoid system
Lymphatic vessels
Lymph (fluid connective tissue)
Lymphoid tissues
Lymphoid organs
Plays central role in body’s defenses against viruses, bacteria, and other microorganisms
Lymphatic vessels originate in peripheral tissues and deliver lymph to the venous system.
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3. An Overview of the Lymphoid System
Lymph consists of:
Interstitial fluid, which resembles blood plasma, but with a lower concentration of proteins
Lymphocytes, cells responsible for the immune response
Macrophages of various types
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4. An Overview of the Lymphoid System
Primary functions of the lymphoid system:
Produce, maintain, and distribute lymphocytes
Maintain normal blood volume and eliminate local variations in the chemical composition of the interstitial fluid
Provide an alternative route for the transport of hormones, nutrients, and waste products
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5. An Overview of the Lymphoid System
Figure 23.1 Lymphoid System
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6. Structure of Lymphatic Vessels
Lymphatic capillaries
Lymphatic vessels (or lymphatics) carry lymph from peripheral tissues to the venous system.
Lymphatic capillaries (or terminal lymphatics) form a complex network within peripheral tissues.
Lymphatics contain internal valves that prevent backflow of lymph/
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7. Structure of Lymphatic Vessels
Two sets of lymphatic vessels:
Superficial lymphatic vessels travel with superficial veins
The subcutaneous layer next to the skin
The loose connective tissues of the mucous membranes
The loose connective tissues of the serous membranes
Deep lymphatic vessels are large lymphatic vessels that accompany the deep arteries and veins.
Collect lymph from skeletal muscles and other organs of the neck, limbs, and trunk, as well as visceral organs in the thoracic and abdominopelvic cavities
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8. Structure of Lymphatic Vessels
Figure 23.2a Lymphatic Capillaries: (a) Association of Blood Capillaries, Tissue, and Lymphatic Capillaries
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9. Structure of Lymphatic Vessels
Figure 23.2b Lymphatic Capillaries: (b) Sectional View
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10. Structure of Lymphatic Vessels
Figure 23.3 Lymphatic Vessels and Valves
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11. Structure of Lymphatic Vessels
Figure 23.4 Lymphatic Ducts and Lymphatic Drainage
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12. Structure of Lymphatic Vessels
Figure 23.5 Major Lymphatic Vessels of the Trunk
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13. Lymphocytes
Lymphocytes are the primary cells of the Lymphoid system, and they are responsible for specific immunity.
They respond to the presence of
Invading organisms, such as bacteria and viruses
Abnormal body cells, such as virus-infected cells or cancer cells
Foreign proteins, such as the toxins released by some bacteria
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14. Lymphocytes Three different classes of lymphocytes in the blood:
T cells (thymus dependent)
Cytotoxic T cells
Helper T cells
Suppressor T cells
Memory T cells
B cells (bone marrow derived)
Plasma cells
Memory B cells
NK cells (natural killer)
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15. Lymphocytes Figure 23.6 Lymphocytes and the Immune Response
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16. Lymphocytes Figure 23.7 Derivation and Distribution of Lymphocytes
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17. Lymphoid Tissues Any tissue containing an abundance of lymphocytes
Diffuse lymphoid tissues—loosely packed lymphocytes within connective tissue
Lymphoid nodules—densely packed lymphocytes within loose connective tissue
Tonsils
Aggregated lymphoid nodules (Peyer’s patches)
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18. Lymphoid Tissues
Figure 23.8a Histology of Lymphoid Tissues: (a) Aggregated Lymphoid Nodule (Intestinal Tract)
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19. Lymphoid Tissues
Figure 23.8b Histology of Lymphoid: (b) Pharyngeal Tonsil (Respiratory Tract)
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20. Lymphoid Organs
Lymphoid tissues that are separated from surrounding tissues by a capsule
Lymph nodes
Thymus
Spleen
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21. Lymphoid Organs Figure 23.9 Structure of a Lymph Node
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22. Lymphoid Organs Figure 23.10 Lymphatic Drainage of the Head and Neck
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23. Lymphoid Organs
Figure 23.11a Lymphatic Drainage of the Upper Limb: (a) Male, Anterior View
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24. Lymphoid Organs
Figure 23.11b Lymphatic Drainage of the Upper Limb: (b) Female, Anterior View
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25. Lymphoid Organs Figure 23.12 Lymphatic Drainage of the Lower Limb
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26. Lymphoid Organs Figure 23.13 A Pelvic Lymphangiogram
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27. Lymphoid Organs
Figure 23.14a, b Lymphatic Drainage of the Inguinal Region: (a) Dissection of the Upper Right Inguinal Region in a Male (b) Inguinal Lymph Nodes and Vessels
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28. Lymphoid Organs
Figure Lymph Nodes in the Large Intestine and Associated Mesenteries
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29. Lymphoid Organs
Figure Anatomy and Histological Organization of the Thymus
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30. Lymphoid Organs
Figure Anatomy and Histological Organization of the Spleen
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31. Lymphoid Organs Figure 23.18 Jan’s X-Ray
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32. Aging and the Lymphoid System
With advancing age, the lymphoid system becomes less effective at combating disease.
T cells become less responsive to antigens.
The number of helper T cells is reduced.
B cells are less responsive.
Antibody levels do not rise as quickly after antigen exposure.
The net result is an increased susceptibility to viral and bacterial infection, and cancer.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings