Lymphatic and immune systems


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Lymphatic and immune systems

  1. 1. Lymphatic and Immune Systems Dragan Nikolic
  2. 2. Components of the Lymphatic and Immune Systems The lymphatic system has at least three different functions: functions – Serves to maintain the fluid balance of our internal body environment – Serves as part of our immune system – Helps regulate the absorption of lipids from digested food in the small intestines and its transport to the large systemic veins
  3. 3. Components of the Lymphatic and Immune Systems (Cont’d) The immune system serves as an internal “security force” to deal with abnormal cells – Repels and destroys microorganisms – Defends us from our own abnormal cells that can cause cancer
  4. 4. Lymphatic System Overview of the Lymphatic System – The lymphatic system solves the problem of fluid retention in tissues • Acts as a drainage system • Collects excess tissue fluid and return it to the venous blood just before it reaches the heart – Lymphatic system is a part of the circulatory system • Consists of moving fluid derived from the blood and tissue fluid, as well as a group of vessels that return the lymph to the blood
  5. 5. Lymphatic System (Cont’d) Lymphatic vessels do not form a closed system of vessels • They begin blindly in the intercellular spaces of the soft tissue of the body
  6. 6. Lymphatic System (Cont’d) Lymph and Interstitial Fluid – Lymph – clear fluid found in the lymphatic vessels – Interstitial fluid – complex fluid that fills the spaces between the cells – Both fluids closely resemble blood plasma in composition – Difference is that lymph cannot clot like blood
  7. 7. Lymphatic System (Cont’d) Lymphatic Vessels – Lymphatic vessels – microscopic blind-ended lymphatic capillaries; wall of each lymphatic capillary consists of a single layer of flattened endothelial cells • Networks of lymphatic capillaries branch and then rejoin repeatedly to form a network throughout the interstitial spaces of our bodies • Lymphatic capillaries merge to form larger and larger vessels until main lymphatic trunks are formed – right lymphatic duct and thoracic duct
  8. 8. Lymphatic System (Cont’d) Structure of lymphatic vessels • Walls of lymphatic capillaries – Have numerous openings or clefts between the cells – As lymph flows from the thin-walled capillaries into vessels with larger diameters, the walls become thicker • Eventually these larger vessels have the three layers typical of arteries and veins • One-way valves are abundant in lymphatic vessels of all sizes
  9. 9. Lymphatic System (Cont’d) Function of lymphatic vessels • Permeability of the lymphatic capillary wall permits very large molecules and even small particles to be removed from the interstitial spaces
  10. 10. Lymphatic System (Cont’d) Circulation of Lymph – About 50% of the total blood protein leaks out of the capillaries into the interstitial fluid; ultimately returns to the blood by way of the lymphatic vessels
  11. 11. Lymphatic System (Cont’d) The lymphatic pump • Lymph moves slowly and steadily along in its vessels into the general circulation at about 3 liters per day – Lymph flow is possible because of the large number of valves that permit fluid flow only in the general direction toward the heart – Breathing movements and skeletal muscle contraction aid in this motion
  12. 12. Lymphatic System (Cont’d) Lymph Nodes – Structure of lymph nodes • Oval-shaped or bean-shaped structures; widely distributed throughout the body • Lymph nodes are linked together by the lymphatic vessels • Fibrous partitions or trabeculae extend from the covering capsule toward the center of a lymph node, creating compartments called cortical nodules • Center, or medulla, of a lymph node is composed of sinuses; separate medullary cords composed of plasma cells and B cells
  13. 13. Lymphatic System (Cont’d) Locations of lymph nodes – Most lymph nodes occur in groups, or clusters – Approximately 500-600 lymph nodes are located in the body Functions of lymph nodes – Defend our bodies from invading pathogens; sites of both biological and mechanical filtration – Provide sites for the maturation of some types of lymphocytes
  14. 14. Lymphatic System (Cont’d) Structure and Function of the Tonsils – Tonsils – form a protective ring under the mucous membranes in the mouth and back of the throat • Protect against bacteria that may invade tissue in the area around the openings between the nasal and oral cavities; first line of defense from the external environment – Tonsils: – Palatine – located on each side of the throat – Pharyngeal tonsils (adenoids) – lie near the posterior opening of the nasal cavity – Lingual – lie near the posterior opening of the nasal cavity
  15. 15. Lymphatic System (Cont’d) Structure and Function of Aggregated Lymphoid Nodules – Also called Peyer patches – small, oval patches or groups of lymph nodes that form protective layer in mucous membrane of the small intestine • Provide protection in a spot that is potentially open to external environment via the mouth • Macrophages and other cells prevent most bacteria from penetrating the gut wall
  16. 16. Lymphatic System (Cont’d) Structure and Function of the Thymus – Thymus – a primary organ of the lymphatic system • Consists of two pyramid-shaped lobes • Located in the mediastinum, extending up into the neck, close to the thyroid gland • Thymus plays a critical part in the body’s defenses against infection • Soon after birth, thymus begins secreting a group of hormones that enable lymphocytes to develop into mature T cells
  17. 17. Lymphatic System (Cont’d) Structure and Function of the Spleen – Spleen – located directly below the diaphragm, just above most of the left kidney and behind the fundus of the stomach • Roughly oval in shape • Spleen has variety of functions: – Defense – Hematopoiesis – Erythrocyte and platelet destruction – Reservoir for blood
  18. 18. Immune System Organization of the Immune System – Identification of cells and other particles: • Antigens – cells, viruses, and other particles with unique molecules on their surfaces – Self – Non-self – molecules on the surface of foreign or abnormal cells or particles that serve as recognition markers by our immune system – Self-tolerance – ability of our immune system to attack abnormal or foreign cells while sparing our own cells • Two categories of defense mechanisms: – Innate immunity (Nonspecific) – Adaptive immunity (Specific)
  19. 19. Immune System (Cont’d) Innate (Non-specific) Immunity Phagocytosis and phagocytic cells • Phagocytosis – ingestion and destruction of microorganisms and other small particles by cells called phagocytes • Phagocytosis is classified as an innate defense • The most numerous type of phagocyte is the neutrophil; other neutrophil types include macrophages and dendritic cells (DC) Chemo-tactic factors cause neutrophils and other phagocytes to adhere to the endothelial lining of capillaries servicing the affected area – After this, phagocytic cells squeeze through the wall of a blood vessel to get to the site of the injury or infection; diapedesis
  20. 20. Immune System (Cont’d) Innate (Non-specific) Immunity – Natural killer cells – provide important innate defensive functions for our bodies • Kill many types of tumor cells and cells infected by different kinds of viruses • Produced in the red bone marrow and make up about 15% of the total lymphocyte number • Recognize markers on surface membrane of invading or defective cells
  21. 21. Immune System (Cont’d) Adaptive immunity – involves mechanisms that program the body to recognize specific threatening agents; specific agents immunity • Primary types of cells involved in innate immunity: – Epithelial barrier cells – Phagocytic cells – Natural killer (NK) cells • Primary types of cells involved in adaptive immunity: – T cells – B cells
  22. 22. Immune System (Cont’d) Adaptive immunity – body’s third line of defense; provided by two different types of lymphocytes • Two major classes of lymphocytes: – B lymphocytes (B cells) – T lymphocytes (T cells) • B cells produce molecules called antibodies that attack the pathogens or direct other cells, such as phagocytes, to attack them; antibodymediated immunity
  23. 23. Immune System (Cont’d) B Cells and Antibody-Mediated Immunity – Diversity of antibodies – every normal baby is born with an enormous number of different clones of B cells – Classes of antibodies – five classes of immuno-globulin antibodies; identified by letter names as immunoglobulins M, E, G, A, and D (USE MNEMONIC: MEGA-D) MEGA-D • IgM – antibody that immature B cells synthesize and insert into their plasma membranes • IgG – most abundant circulating antibody; cross-placental barrier during pregnancy to give passive immunity to baby • IgA – major class of antibody in the mucous membranes of the body; also in saliva and tears • IgE – produce the major symptoms of allergies and kill parasites • IgD – small amount in blood; function unknown
  24. 24. Immune System (Cont’d) Types of Adaptive Immunity – Acquired immunity – classified as either natural immunity or artificial immunity • Natural immunity – results from nondeliberate exposure to antigens • Artificial immunity – results from deliberate exposure to antigens; immunizations
  25. 25. Immune System (Cont’d) Types of Adaptive Immunity – Natural and artificial immunity may be “active” or “passive • Active immunity – results when an individual’s own immune system responds to a harmful agent— regardless of how it was encountered • Passive immunity – results when immunity to a disease that has developed in another individual is transferred to an individual who was not previously immune
  26. 26. References • Hill, David J., (2012) Essentials of Anatomy and Physiology, Mosby, St. Louis. ISBN 9780323085113 • Metchnikoff, Elie; Translated by F.G. Binnie. (1905). Immunity in Infective Diseases (Full Text Version: Google Books). Cambridge University Press. ISBN 68025143