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The Lymphatic System Lymphatic system functions

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Presentation on theme: "The Lymphatic System Lymphatic system functions"— Presentation transcript:

1 The Lymphatic System Lymphatic system functions
Transport fluids from body tissues back to bloodstream Play essential roles in body defense and resistance to disease Consists of two semi-independent parts: Lymphatic vessels Lymphoid tissues and organs

2 Lymphatic Characteristics
Lymph – excess tissue fluid carried by lymphatic vessels Pale white fluid, similar composition to blood plasma, but with more leukocytes, lymphocytes, and triglycerides

3 Lymphatic Vessels Lymphatic vessels
Carry lymph towards the heart, never away No pump, moved by “milking” action of muscles

4 Lymphatic Vessels Lymphatic vessels
Fluid leaks into lymphatic capillaries from body tissue Lymphatic collecting vessels collect it from lymph capillaries Carries lymph to and away from lymph nodes Figure 12.1

5 Lymphatic Vessels Figure 12.2

6 Lymphatic Vessels Lymphatic collecting vessels (continued)
Returns fluid to circulatory veins near the heart Figure 12.1

7 Lymph As lymph seeps into lymph capillaries, harmful materials are carried with it: Bacteria Viruses Cancer cells Cell debris

8 Lymph Nodes Lymph nodes filter lymph before it is returned to the blood

9 Lymph Nodes Leukocyte defense cells within lymph nodes:
Macrophages – engulf and destroy foreign substances Lymphocytes – provide immune response to antigens

10 Other Lymphoid Organs Several other organs contribute to lymphatic function Spleen Thymus Tonsils Peyer’s patches Figure 12.5

11 The Spleen Spleen: Filters out and destroys worn out blood cells
Acts as a blood reservoir Synthesizes antibodies, filters antibody-coated cells from blood

12 The Thymus Thymus: Produces hormones (like thymosin) to program (“educate”) certain lymphocytes

13 Tonsils Tonsils: Small masses of lymphoid tissue around the pharynx
Trap and remove bacteria and other foreign materials

14 Peyer’s Patches Peyer’s Patches:
Found in the wall of the small intestine Capture and destroy bacteria in the intestine

15 Body Defenses The body is constantly in contact with bacteria, fungi, and viruses The body has two defense systems for foreign materials: nonspecific and specific

16 Body Defenses Nonspecific defense system
Mechanisms protect against a variety of invaders Responds immediately to protect body from foreign materials Specific defense system Specific defense is required for each type of invader Also known as the immune system

17 Body Defenses Figure 12.6

18 Nonspecific Body Defenses
First Line of Defense: Body surface coverings and their secretions Intact skin - physical barrier, acidic pH Mucous membranes - mucus, protein-digesting enzymes, HCl (in stomach)

19 Nonspecific Body Defenses
Second Line of Defense: Non-specific defense cells Phagocytes (like macrophages) - engulf & digest foreign matter Natural killer (NK) cells - lyse & destroy cancerous or virus-infected cells Antimicrobial chemicals The inflammatory response Fever

20 Antimicrobial Chemicals
Two kinds: Complement, Interferon Complement Plasma proteins Lyse microorganism, enhance phagocytosis Figure 12.10

21 Antimicrobial Chemicals
Interferon Secreted proteins of virus-infected cells Bind to healthy cell surfaces to inhibit viruses binding

22 Inflammatory Response
Inflammation: an increase in blood flow, tissue fluid, and clotting proteins in a specific area Prevents spread of foreign agents to neighboring tissues, disposes of pathogens & debris, promotes tissue repair, releases chemicals that attract immune cells Triggered when body tissues are injured Signs: redness, heat, swelling, pain

23 Steps in the Inflammatory Response
Figure 12.8

24 Fever Abnormally high body temperature
Hinders pathogens with temperature preferences Increases mobility of leukocytes, rate of phagocytosis, production rate of certain lymphocytes

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