Lymphatic Powerpoint

• Lymphatic system


  Consists of lymphatic vessels and lymphoid tissues/organs<|>Functions to transport escaped fluids from cardiovascular system back to blood<|>Plays essential roles in body defense and resistance to disease

  
• Lymphatic vessels

  • Form a one-way system with lymph flowing only toward the heart
  • Lymph capillaries weave between tissue cells and blood capillaries with overlapping walls to form minivalves
  • Lymphatic collecting vessels collect lymph from capillaries and return it to circulatory veins near the heart

  
• Lymph transport

  1. Aided by milking action of skeletal muscles

  2. Aided by pressure changes in thorax during breathing

  3. Aided by smooth muscle in walls of lymphatics

  
• Lymph nodes

  Filter lymph before it is returned to blood<|>Contain defense cells like macrophages and lymphocytes that destroy harmful materials in lymph

  
• Structure of lymph nodes

  • Kidney-shaped, less than 1 inch long, surrounded by capsule and divided into compartments
  • Cortex contains follicles with lymphocytes, medulla contains phagocytic macrophages
  • Lymph enters through afferent vessels, flows through sinuses, and exits through fewer efferent vessels

  
• Other lymphoid organs

  • Spleen
  • Thymus
  • Tonsils
  • Peyer's patches
  • Appendix
• Spleen

  Filters and cleans blood, provides site for lymphocyte proliferation, destroys worn-out red blood cells, stores platelets

  
• Thymus


  Functions at peak levels only during youth
• Tonsils


  Trap and remove bacteria and other foreign pathogens entering the throat
• Peyer's patches and appendix

  Contain macrophages that capture and destroy bacteria in the intestine
• Mucosa-associated lymphoid tissue (MALT)


  Acts as a sentinel to protect respiratory and digestive tracts from foreign matter
• Innate (nonspecific) defense system


  Responds immediately to protect body from all foreign materials, includes skin, mucous membranes, inflammatory response, various proteins
• Adaptive (specific) defense system


  Fights invaders that get past the innate system, requires specific resistance to each type of invader
• Innate (nonspecific) body defenses

  • Phagocytes
  • Natural killer cells
  • Inflammatory response
  • Antimicrobial chemicals (complement, interferons, acidic fluids)
  • Fever
• Surface membrane barriers


  Provide first line of defense, include skin and mucous membranes with protective secretions
• Inflammatory response

  1. Triggered by tissue injury

  2. Causes redness, heat, pain, swelling

  3. Damaged cells release inflammatory chemicals like histamine and kinin

  4. Causes blood vessel dilation, capillary leakage, and migration of phagocytes/white blood cells to the area

  5. Prevents spread of damaging agents, disposes of debris/pathogens, sets stage for repair

  
• Neutrophils migrate to the area of inflammation as part of the inflammatory response
• Inflammation


  Redness<|>Heat<|>Pain<|>Swelling (edema)
• Inflammatory response

  1. Damaged cells release inflammatory chemicals

  2. Histamine

  3. Kinin

  4. Blood vessels dilate

  5. Capillaries become leaky

  6. Phagocytes and white blood cells move into the area

  
• Functions of the inflammatory response

  • Prevents spread of damaging agents to nearby areas
  • Disposes of cell debris and pathogens
  • Sets the stage for repair
• Process of the inflammatory response

  1. Neutrophils migrate to the area of inflammation by rolling along the vessel wall

  2. Neutrophils squeeze through the capillary walls by diapedesis to sites of inflammation

  3. Neutrophils gather in the precise site of tissue injury and consume any foreign material present

  
• Phagocytes


  • Cells such as neutrophils and macrophages engulf foreign material by phagocytosis
  • The phagocytic vesicle is fused with a lysosome, and enzymes digest the cell's contents
• Antimicrobial proteins

  Enhance innate defenses by attacking microorganisms directly and hindering reproduction of microorganisms
• Complement proteins

  A group of at least 20 plasma proteins that circulate in the plasma and are activated when they encounter and attach to cells
• Activation of complement

  1. Membrane attack complexes (MACs) produce holes or pores in cells, allowing water to rush in and the cell to burst (lyse)

  2. Activated complement enhances the inflammatory response
• Interferons


  Small proteins secreted by virus-infected cells that bind to membrane receptors on healthy cell surfaces to interfere with the ability of viruses to multiply
• Fever


  Abnormally high body temperature is a systemic response to invasion by microorganisms<|>The hypothalamus thermostat can be reset higher by pyrogens (secreted by white blood cells)<|>High temperatures inhibit the release of iron and zinc (needed by bacteria) from the liver and spleen<|>Fever also increases the speed of repair processes
• Adaptive body defenses


  The body's specific defense system, or the third line of defense<|>Immune response is the immune system's response to a threat<|>Antigens are targeted and destroyed by antibodies
• Three aspects of adaptive defense

  • Antigen specific
  • Systemic
  • Memory
• Two arms of the adaptive defense system

  • Humoral immunity (antibody-mediated immunity)
  • Cellular immunity (cell-mediated immunity)
• Antigens

  Any substance capable of exciting the immune system and provoking an immune response<|>Nonself antigens are foreign intruders<|>Self-antigens do not trigger an immune response in us but can be strongly antigenic to other people<|>Haptens, or incomplete antigens, are not antigenic by themselves but can trigger an immune response when linked with our own proteins
• Cells of the adaptive defense system

  • Lymphocytes (B cells and T cells) respond to specific antigens
  • Antigen-presenting cells (APCs) help the lymphocytes but do not respond to specific antigens
• Lymphocyte differentiation and activation

  1. Lymphocytes become immunocompetent in the thymus (T cells) or bone marrow (B cells)

  2. Immunocompetent lymphocytes migrate to lymph nodes and spleen where they encounter antigens

  3. Differentiation from naïve cells into mature lymphocytes is complete when they bind with recognized antigens

  
• Humoral (antibody-mediated) immune response

  1. B lymphocytes with specific receptors bind to a specific antigen and are stimulated to undergo clonal selection

  2. Most of the B cell clone members become plasma cells that produce antibodies to destroy antigens

  3. Some B cells become long-lived memory cells that provide immunological memory
• Active immunity


  Occurs when B cells encounter antigens and produce antibodies<|>Can be naturally acquired during infections or artificially acquired from vaccines
• Passive immunity


  Occurs when antibodies are obtained from serum of an immune human or animal donor<|>Naturally acquired from a mother to her fetus or in breast milk, or artificially acquired from immune serum or gamma globulin<|>Provides short-lived protection and does not result in immunological memory
• Active immunity

  Benefits of vaccines:

  • Spare the signs and symptoms of the disease that would otherwise occur during the primary response
  • Weakened antigens still stimulate antibody production and promote immunological memory
• Passive immunity


  Occurs when antibodies are obtained from serum of an immune human or animal donor:

  • Naturally acquired from a mother to her fetus or in the breast milk
  • Artificially acquired from immune serum or gamma globulin (donated antibodies)
  • Antivenom, antitoxin
  • Immunological memory does not occur
  • Protection is short-lived (2–3 weeks)
• Monoclonal antibodies


  Antibodies prepared for clinical testing for diagnostic services:

  • Produced from descendants of a single cell line
  • Exhibit specificity for only one antigen
  • Examples of uses: cancer treatment, diagnosis of pregnancy, treatment after exposure to hepatitis and rabies
• Antibodies (immunoglobulins, Igs)

  Constitute gamma globulin part of blood proteins, soluble proteins secreted by activated B cells (plasma cells), formed in response to a huge number of different antigens