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The Lymphatic System

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  1. The Lymphatic System

  2. The Lymphatic System • Two parts • Lymphatic vessels • Transport fluids that have escaped from the blood vascular system back to the blood • Lymphoid tissues and organs • House phagocytic cells and lymphocytes, which help in body defense and resistance to disease

  3. The Lymphatic System • Lymph Fluid • Fluid (plasma) gets pushed out of blood stream at the capillaries • This extra fluid remains in the tissue spaces, but must be returned to blood stream • Before it does so, it passes through lymph tissues & organs

  4. The Lymphatic System • Lymph Flow • Lymph flows only toward the heart • Means that lymphatic vessels are a one-way system

  5. The Lymphatic System • Lymphatic Capillaries • Form a “spiderweb” between the tissue cells and the blood capillaries in the loose connective tissues of the body • Very Permeable • Have “minivalves” that open one-way to let in fluid if pressure is high • Capillaries join to form collecting vessels, which make their way to the collecting ducts

  6. The Lymphatic System • Collecting Ducts • Right Lymphatic Duct • Drains lymph from right arm and right side of head and thorax • Thoracic Duct • Drains lymph from rest of body • Both ducts empty the lymph into the subclavian veins, so fluid can return to the blood vessels

  7. The Lymphatic System • Lymph Nodes • Filter lymph before it is returned to the blood – contains macrophages and lymphocytes to help! • Materials returned to the blood… • Water • White Blood cells • Proteins

  8. The Lymphatic System • Harmful materials that lymph nodes remove… • Bacteria • Viruses • Cancer (tumor) cells • Cell debris

  9. The Lymphatic System • Pathogens: harmful or disease-causing microorganisms • A general term for anything foreign that enters our body

  10. The Lymphatic System • Clusters of Lymph Nodes found at… • Inguinal Region (Groin) • Axillary Region (Armpit) • Cervical Region (Neck) • Note: approx. 500 to 1500 nodes in the body

  11. The Lymphatic System • Macrophages • Engulf and destroy foreign pathogens such as bacteria and viruses • Lymphocytes • Provide immune response to foreign substances • Two types: B cells and T cells

  12. The Lymphatic System • Swollen lymph nodes are due to the trapping of foreign substances in the nodes • Lymph travels through several lymph nodes before it returns to the blood • Only the lymph nodes filter lymph!

  13. The Lymphatic System • Several other organs contribute to lymphatic function • Spleen • Thymus • Tonsils • Peyer’s patches

  14. The Lymphatic System • Spleen • Located on the left side of the abdomen • Filters blood of bacteria, viruses, and debris • Destroys worn out blood cells • Acts as a blood reservoir

  15. SP – spleen, ST – stomach, LLL – left lobe of liver, FL – falciform ligament, DP – diaphragm, PCL – phrenicocolic ligament, DC – descending colon

  16. The Lymphatic System • Thymus • Located low in the throat, overlying the heart • Functions at peak levels only during childhood • Produces hormones (like thymosin) to program lymphocytes

  17. The Lymphatic System • Tonsils • Small masses of lymphoid tissue around the pharynx • Trap and remove bacteria and other foreign materials during breathing & eating

  18. The Lymphatic System • Peyer’s Patches • Found in the wall of the small intestine • Capture and destroy bacteria in digesting food

  19. The Lymphatic System • The body is constantly in contact with bacteria, fungi, and viruses (all considered pathogens) • The body has two defense systems for foreign materials

  20. Types of Defense • Non-Specific Defense • First & Second Line of Defense • Doesn’t care what the pathogen is – your body will be defended!

  21. Non-Specific Defense • Non-Specific Defense Mechanisms Include… • Skin: mechanical barrier, acidic skin secretions can also defend • Mucous Membranes: Mucus and nasal hairs trap microorganisms; Cilia move mucus out of body; Gastric juice, saliva, and tears have enzymes that destroy microorganisms • Skin and Mucous Membranes are the first line of defense against pathogens • Cellular & Chemical Defense: Second line of defense; includes…

  22. Non-Specific Defense • Phagocytes: • Cell that engulfs a foreign particle, enclosing it in a vacuole; destroyed with enzymatic contents of lysosomes

  23. Non-Specific Defense • Examples of phagocytes include macrophages (in body tissues, developed from monocyte WBC), and neutrophils (WBC)

  24. Macrophage engulfing E-Coli

  25. Non-Specific Defense • Natural Killer Cells: • Defensive cells that can kill cancer cells and virus-infected body cells • Release chemicals to destroy invader’s cell membrane and nucleus

  26. Non-Specific Defense • Inflammatory Response: • Non-specific response triggered whenever body tissues are injured

  27. Non-Specific Defense • Benefits of inflammatory response include: • Preventing the spread of damaging agents to nearby tissues • Disposes of cell debris and pathogens • Sets the stage for repair

  28. Non-Specific Defense • 4 Signs of Inflammatory Response: • Redness – due to dilation of blood vessels in area, bringing more clotting proteins/ oxygen/nutrients to the area • Heat – due to dilation of blood vessels in area, helps increase metabolic rate of cells • Swelling – due to plasma (lymph) leaking from blood stream into tissue spaces • Pain – pain receptors activated by plasma leaking

  29. Non-Specific Defense • All of the above symptoms are due to the inflammatory chemicals (including histamine and kinins) that are released when cells are damaged

  30. Non-Specific Defense • Fever: response to invading pathogens • Hypothalamus will reset internal temperature based on presence of pyrogens (chemicals secreted by WBC exposed to foreign substances) • Fever inhibits the release of iron and zinc from liver and spleen needed by bacteria • Fever also increases the speed of tissue repair, but if fever gets too high, it can screw up enzymes and proteins

  31. Specific Defense • Specific Defense • Third line of defense • AKA immune system • Plans defense based on specific type of pathogen/antigen (The antigen is a marker on the pathogen!) • Must first have an initial exposure before it can protect the body against the pathogen • Involves the Lymph Vessels/Nodes and Lymphoid Organs (Tonsils, Thymus, Spleen, and Peyer’s Patches)

  32. Specific Defense • 2 Types of Response: Humoral and Cell-Mediated

  33. Specific Defense • 3 important aspects of immune response: • Antigen specific – recognizes and acts against particular foreign substances • Systemic – not restricted to the initial infection site • Has memory – recognizes and mounts a stronger attack on previously encountered pathogens

  34. Specific Defense • Antigens: any substance capable of exciting our immune system and provoking an immune response • A foreign signal on the outside of a pathogen! • Examples of common pathogens/antigens • Foreign proteins (ex: blood typing) • Pollen grains • Microorganisms (bacteria, fungi, virus) • Side Note: Our immune cells do not attack our own proteins, but our cells in another person’s body can trigger an immune response because they are foreign (think: organ transplants, blood donation)

  35. Immune System Review • Types of cells involved • Lymphocytes (WBC): two types… • B Cells: help with humoral defense, produce antibodies • T Cells: help with cell-mediated defense, do not produce antibodies

  36. Specific Defense • Both types of lymphocytes originate from red bone marrow • What determines if it will be a B or T cell is where in the body it becomes immunocompetent (capable of responding to a specific antigen) • T Cells: lymphocytes migrating to thymus • B Cells: lymphocytes develop in bone marrow

  37. Specific Defense • Our genes determine what specific foreign substances our immune system will be able to recognize and resist – they only become “activated” once exposed to the antigen

  38. FYI: Because of the structure of human DNA (deoxyribonucleic acid; the genetic material determining the makeup of all cells), humans are not subject to certain diseases that dogs and other animals are, and vice-versa. For example, humans cannot contract distemper; however, dogs and cats can. Conversely, humans can suffer from measles; dogs and cats cannot. The genetic makeup of human cells (and of animal and plant cells, also) makes it impossible for certain pathogens to infect and reproduce in those cells.

  39. Specific Defense • After becoming immunocompetent, both T and B cells migrate to the lymph nodes and spleen, but can be found throughout lymphatic vessels

  40. Specific Defenses • Macrophages: • Arise from monocytes (WBC) formed in the bone marrow • Job is to engulf foreign particles (part of non-specific defense) and present fragments of these antigens on their surface (so T Cells can recognize them and become activated, helping out specific defense!)