Lymphatic system

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1. Lymphatic System 2. Introduction – Components ã Lymph is the fluid ã Vessels – lymphatics ã Structures & organs – Functions ã Return tissue fluid to…
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  • 1. Lymphatic System
  • 2. Introduction – Components • Lymph is the fluid • Vessels – lymphatics • Structures & organs – Functions • Return tissue fluid to the bloodstream • Transport fats from the digestive tract to the bloodstream • Surveillance & defense
  • 3. The Lymphatic System
  • 4. Lymphatic's – Originate as lymph capillaries – Capillaries unite to form larger vessels • Resemble veins in structure • Connect to lymph nodes at various intervals – Lymphatics ultimately deliver lymph into 2 main channels • Right lymphatic duct – Drains right side of head & neck, right arm, right thorax – Empties into the right subclavian vein • Thoracic duct – Drains the rest of the body – Empties into the left subclavian vein
  • 5. How is fluid moved? Contraction of skeletal muscles against lymphatic vessels Smooth muscle contraction Valves in lymphatic vessels Breathing Obstruction of system leads to edema
  • 6. Lymph Tissue – 3 types • Diffuse lymphatic tissue – No capsule present – Found in connective tissue of almost all organs • Lymphatic nodules – No capsule present – Oval-shaped masses – Found singly or in clusters • Lymphatic organs – Capsule present – Lymph nodes, spleen, thymus gland
  • 7. Lymph Nodes – Oval structures located along lymphatics – Enclosed by a fibrous capsule – Cortex = outer portion • Germinal centers produce lymphocytes – Medulla = inner portion • Medullary cords – Lymph enters nodes through afferent lymphatics, flows through sinuses, exits through efferent lymhpatic
  • 8. Tonsils – Multiple groups of large lymphatic nodules – Location – mucous membrane of the oral and pharyngeal cavities – Palatine tonsils • Posterior-lateral walls of the oropharynx – Pharyngeal tonsil • Posterior wall of nasopharynx – Lingual tonsils • Base of tongue
  • 9. Tonsils
  • 10. Spleen – Largest lymphatic organ – Located between the stomach & diaphragm – Structure is similar to a node • Capsule present • But no afferent vessels or sinuses – Histology • Red pulp contains all the components of circulating blood • White pulp is similar to lymphatic nodules – Functions • Filters blood • Stores blood
  • 11. Spleen Filters blood, while lymph nodes filter lymph White pulp- concentration of lymphocytes (around arteries) Red pulp- red cells are filtered too Macrophages are plentiful throughout
  • 12. Spleen Functions • Phagocytosis • Storage of Blood (350 ml) • Immune Response • Erythropoesis (in Fetus and Sometimes in Adults)
  • 13. Thymus Gland – Location – behind the sternum in the mediastinum – The capsule divides it into 2 lobes – Development • Infant – conspicuous (Highly Prominent) • Puberty – maximum size • Maturity – decreases in size – Function • Differentiation and maturation of T cells
  • 14. Thymus T cell development: cells migrate from bone marrow and differentiate into T cells T helper cells Cytotoxic T cells Thymus gets progressively smaller (and less active) through life
  • 15. Thymus Gland
  • 16. Function of the Lymphatic System – Defense against harmful organisms and chemicals – 2 types of defense • Nonspecific • Specific – Specific defense = immunity • Humoral immunity involves B cells that become plasma cells which produce antibodies that bind with specific antigens. • Cell-mediated immunity involves T cells that directly destroy foreign cells
  • 17. Derivation and Distribution of Lymphocytes
  • 18. What do antibodies do? (five classes) Ig (immunoglobulin) G- active in blood against bacteria and viruses helps activate complement helps phagocytes eliminate antigens most common antibody in the blood IgM- reacts with certain antigens, usually on first exposure IgA- most common in mucosa
  • 19. IgD and IgE are rare in blood IgE is involved in allergic reactions sticks to mast cells, which release inflammatory substances IgD is usually found on B cells (not released) may be involved in B cell activation
  • 20. When the body is exposed to an antigen for the first time, antibody production is slow and at low levels. Usually IgM If exposed to the same antigen again, the antibody response is much more rapid and intense (IgG) (Most antibody in the blood stream is IgG)
  • 21. Autoimmunity Normally immune system does NOT react to “self” antigens Autoimmunity occurs when it does disease can be localized (to kidneys, joints, thyroid, etc.) or can be systemic (lupus) Treatment usually requires some form of immunosuppression
  • 22. Summary The lymphatic system helps maintain homeostasis of fluids, and also helps remove antigen from the body The immune system consists of barriers (physical and chemical) and specific and nonspecific mechanisms to eliminate antigen “Immune cells” are blood cells. Some circulate in the blood and can then migrate into tissues at site of injury. These include neutrophils and macrophages.
  • 23. All blood cells arise in the bone marrow. B lymphocytes initially develop in the bone marrow and then migrate to lymphoid tissues (esp. lymph nodes and spleen) T lymphocytes develop in the thymus. B cells produce antibodies, which interact with antigen to help eliminate it. Helper T cells regulate the immune response; cytotoxic T cells kill virus-infected cells and probably tumor cells. (They also are responsible for transplant rejection.)
  • 24. B and T cell response is antigen-specific and has “memory” (second response is faster and stronger than the first) Immune system can be overly responsive to antigens (hypersensitivity/allergy) or can mistakenly be directed against self antigen (autoimmunity) Immune deficiencies leave people vulnerable to infection
  • 25. Lymph Vessel Pathology • Tumor Fragments • Infection Lymphangitis Lymphadenitis Lymphadenopathy Spleenomegaly Lymphoedema
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