chapter 21.docx

Chapter 21 Lymphatic system Plays a vital role supporting both cardiovascular Immune systems If maintains homeostasis by returning most of the fluid that has been diverted back to the blood. If this doesn’t happen, things like your ankles swell up like balloons, your lungs could fill up with fluid a...

Chapter 21 Lymphatic system Plays a vital role supporting both cardiovascular Immune systems If maintains homeostasis by returning most of the fluid that has been diverted back to the blood. If this doesn’t happen, things like your ankles swell up like balloons, your lungs could fill up with fluid and your blood volume and pressure would drop to the point that you would eventually die. The system is made up of 3 main parts Lymph a watery fluid that flows through the system Starts out as blood plasma that gets forced out of capillaries. The capillaries reabsorb some of the fluid but a lot gets left behind. About 15% of that fluid enters the L system So as this system picks up that fluid and takes it where it needs to go, it is also checked along the way by passing through lymph nodes where some immune cells are checking for foreign matter. If something is found, an immunes response is initiated. Lymph vessels Transports the lymph and lymph nodes 600 to 700 nodes that basically monitor and filter the fluid Lymphoid organs Spleen, thymus, adenoids, and tonsils Starting at the capillary beds, out of 20 liters that circulate through only 17L is taken back up. The other 3L becomes lymph that is picked up by lymphatic capillaries that are located among the blood capillaries Lymphatic capillaries Like arteries and veins have 3 tunicas. They also have 1 way flap that opens to let fluid in when the pressure in the interstitial space is greater than the pressure inside the vessel. L. capillaries merge with collecting vessels which conveye to form larger lymphatic trucks, which drain into 2 major ducts: The right lymphatic duct Drains all the lymph collected from the upper right area of torso, the right arm and the right side of head and thorax. Dumps it all into the internal jugular vein. The larger thoracic duct Takes lymph from the rest of the body and dumps it into the subclavian vein. Lymph nodes This is where the lymph is filtered and inspected by lymphocytes of the immune system. Lymphocytes can recruit other immune cells or activate the immune system depending on what foreign material they encounter. Cells of immune system - associated with lymphatic system Neutrophils – antibacterial cells most common kills 1 and dies. Creates pus. Collected in certain areas. Detects rogue cells - cancer Natural killer cells – lymphocytes that attack and destroy infected host cells and cancerous cells T lymphocytes (T Cells) - mature in the thymus. Infection has already occurred Takes signals from macrophages to make helper t-cells Cytotoxic – t-cells – kill the infected cells. B lymphocytes (B cells) - produce antibodies Macrophages – phagocytic cells and are antigen presenting cells Dendritic cells – another type of phagocytic cell found in skin and mucous membranes. Lymph tissue – scattered throughout the body. More prevalent in areas exposed (open) to outside environments. Respiratory system, digestive, reproductive, urinary. Leukocytes – have all over access except the brain. Inflammation – mast cells. They release histamines that bring leukocytes WBC. Lymphatic organs Spleen – filters blood, RBC graveyard Red bone marrow – hemopoietic function – creates red blood Thymus – nursery for t – cells Secrete hormones – thymosin, thymopoietin, thymulin Lymphadenitis – swollen glands – in response to foreign antigen Lymphadenopathy – disease of any of the lymph nodes. Lymph nodes and metastic cancer – cancer cells break off a go to closest lymph nodes. Create new tumors. This destroys the lymph node and on to the next. Immunity Innate immunity – born with this one. Non-specific Usually the first immune response Since non-specific has no memory 3 mechanisms 1st line of defense – skin and mucus membrane Protective barrier (physical barrier) 2nd line of defense – cellular components Leukocytes, macrophages, killer cells 3rd line of defense – adaptive immunity – acquired immunity Cells do have memory This is in response to specific antigens Cells start innate response by a T-cell. They form memories that present to the other cells. B-cell – memory cell, hemoresponse. B-cells make b-helper. Foreign substance – pathogen or antigen Normal flora – out competes for space and food. Bacteria cannot take up space. Lymph tissue Scattered throughout the body Prevalent in parts of body that open to the exterior Respiratory digestive urinary and reproductive tracts Mucosa – associated lymphoid tissue – MALT Lymphoid organs Primary organs included Red bone marrow and thymus Red bone marrow ---> Hematopoiesis Thymus – nursery for T-cells Secretes hormones: Thymosin Thymopoietin Thymulin Involved in T-Cell development Tonsils Guard against ingested or inhaled pathogens Spleen Makes lymphocytes, filters the blood, stores blood cells, and destroys old blood cells. Responses Lymphadenitis Swollen glands in response to foreign antigen Lymphadenopathy Refers to all diseases of lymph nodes Lymph nodes and Metastatic cancer Cancerous cells break free from original tumor Travel to other sites and form new tumors Tend to lodge in the first lymph node they encounter Multiply and eventually destroy the lymph node They tend to spread to the next node down stream Cancer nodes (and some tumors) usually swollen, firm, and painless. Innate immunity Immunity you are born with and last your entire life It is the first response to a foreign substance Non-specific and has no memory 3 defense mechanisms of innate immunity Physical barriers (1st line of defense) Skin, mucous membranes Cellular components (2nd line of defense) Leukocytes, macrophages, anti-microbial proteins, natural killer cells, fever, inflammation Anti-microbial proteins – Interferons are a type of signaling protein. Made in response to the presence of pathogen like a virus, bacteria, parasite or tumor cell. Adaptive immunity (3rd line of defense) Acquired immune system Immunological memory after an initial response to specific pathogen This leads to a stronger response if exposed to it again. Adaptive Immunity Two forms: 1. Cellular (cell-mediated) immunity 2. Humoral (antibody-mediated) immunity 1. Cellular immunity Lymphocytes directly attack and destroy foreign cells or diseased host cells Intracellular Ridding the body of pathogens inside human cells where antibodies cant reach them. T-cell Also acts against parasitic worms, cancer cells and transplanted cells Humoral immunity B-cells Mediated by antibodies that do not directly destroy a pathogen but tag it for destruction. Effective against extracellular viruses, bacteria, yeasts, protozoans and non-cellular disease agents such as toxins, venoms, and allergens Other forms of Adaptive Immunity include: Active and Passive Active immunity Natural active Production of antibodies as a result of infection Passive immunity Natural passive Antibodies produced by another person Antibodies transferred to baby through breast milk or through the placenta Artificial Active Production of antibodies after exposure to pathogen through artificial means Vaccination Artificial passive Artificial passive Antibodies produced – in another person or animal and you receive it either through blood plasma or serum Anti-serum for snake bites, rabies, botulism, tetanus for example Antibodies or Immunoglobulins Structure All four chains have a variable region that makes the antibody unique. The V region of each hearing and light chains pair combine to form Antigen-binding site. The C region determines the mechanism of the antibodies action. Doesn’t bind complement proteins There are 5 class of antibodies named for the structure of their C regions Ig A – Alpha Found in secretions such as tears, saliva, breast milk Provides protection against mucosal infections Ig D – Delta Found on surface of B cells, involved in B cell activation Ig E – Epsilon Involved in allergic responses, triggers release of histamine and other inflammatory molecules Stimulates eosinophils actions against parasites Ig G – Gamma Most abundant provides long term protection against viruses and bacteria, crosses the placenta to protect the fetus Ig M – Mie First antibody produced in response to infection, found in blood and lymphatic fluid Predominant antibody in primary response Human immune system capable of as many as 1 Trillion different antibodies But there are only at 20,000 genes in the human genome. So the variety of proteins must be accomplished by: Somatic recombination DNA segments shuffled and form new combinations of base sequences to produce antibody genes Somatic hypermutation B cells in lymphoid nodules rapidly mutate creating new sequences Lymphocytes Natural killer cells – innate immunity T-cells -----> B-cells -----> Both adaptive immunity T-cells Developmental stages “Born” in bone marrow “trained” in thymus T-cells are tested by being presented with self-antigens. If they react to self-antigen – they fail, they are eliminated Anergy = self-reactive T-cells remain alive but are unresponsive Sent out to body to carry out ----> immune functions B-cells Develop entirely in bone marrow Those that react to self-antigens also undergo anergy Self-tolerant B cells make antigen surface receptors, divide quickly and produce immunocompetent clones. They leave bond marrow and move to other lymphoid tissues Cellular immunity T-cells directly attack and destroy diseased or foreign cells General stages of response: recognition, attack, memory Recognition Antigen presenting cell. Migrate to nearest lymph node and displaces it to the T-cells Attack T cell “docks” with diseased or foreign cells and delivers a lethal dose of chemicals to destroy it. Memory T cells can become memory cells Next time the response to antigens is much faster Humoral immunity More indirect method. Does not attach enemy cells but instead B cells produce antibodies that bind to antigens and tag them for destruction by other means. Hypersensitivity Immune response Refers to an excessive immune reaction against antigens that most people tolerate Four types: based on whether it involves antibodies or T-cells and how they attack the antigen Type 1 (Acute) Hypersensitivity Includes most common allergens Ig E mediated reaction that begins within seconds of exposure Usually subsides within 30 minutes Clinical symptoms: edema congestion, watery eyes, runny nose, hives and sometimes cramps, diarrhea and vomiting Asthma – most common chronic illness in kids Anaphylaxis – severe and immediate reaction CAN BE FATAL Type 2 Antibody – dependent cytotoxic hypersensitivity Ig G or Ig M attacks antigen Macrophages, phagocytize and destroys platelets, RBCs or other cells Blood transfusion reaction and some drug reactions Type 3 – immune complex immunity Occurs when Ig G or Ig M forms antigen-antibody complex Ex – autoimmune disease – acute glomerulonephritis and systemic lupus erythematosus Type 4 – delayed hypersensitivity Cell-mediated reaction 12-72 hours after exposure Is a result of innate and other immune responses Reactions to cosmetics, soaps, poison ivy, graft rejection, TB skin test, and beta cell destruction that causes type 1 diabetes Autoimmune disease This occurs primarily because the immune system does not distinguish between self and foreign antigens. This could be due to: Cross-reactivity --> Antibodies react to very similar self-antigens Rheumatic fever Changes in structure and self-antigens ---> Viruses and drugs may change structure.