Anatomy & Physiology

 2 Main Parts  Lymphatic vessels  Lymphoid tissues/organs  FUNCTIONS:  Drain excess fluid (edema) and returns it to blood  Plays essential roles in body defense and resistance to disease

 Lymph—excess tissue fluid  Properties of lymphatic vessels  One way system toward the heart  No pump  Lymph moves toward the heart Transported through milking action of skeletal muscle Rhythmic contraction of smooth muscle in vessel walls helps pump the lymph through the system

 Lymph capillaries  Walls overlap to form flap-like minivalves to allow entrance for lymph Fluid leaks into lymph capillaries  Lymph Capillaries are anchored to connective tissue by filaments  Higher pressure on the inside of the capillary closes minivalves Fluid is forced along the vessel for examination Examined by cells of immune system for any potential threats

 Lymphatic collecting vessels  Collect lymph from lymph capillaries  Carry lymph to and away from lymph nodes  Return fluid to circulatory veins near the heart Right lymphatic duct Drains lymph to right arm/head/thorax Thoracic duct Drains rest of body that R.Lymph duct doesn’t

 Harmful materials that enter lymph vessels  Bacteria  Viruses  Cancer cells  Cell debris

 Filter lymph before it is returned to the blood  Areas of high concentration?  Inguinal, axillary, and cervical regions  Defense cells within lymph nodes  Macrophages—engulf and destroy foreign substances  Lymphocytes—provide immune response to antigens  Nodes swell when fighting infection because nodes have engulfed the foreign substance to prevent it from spreading

 Most are kidney- shaped and less than 1 inch long  Cortex  Outer part  Contains follicles— collections of lymphocytes  Medulla  Inner part  Contains phagocytic macrophages

 Several other organs contribute to lymphatic function  Spleen  Thymus  Tonsils  Peyer’s patches

 Blood filled organ which filters blood  Location: Left side of abdomen above diaphragm  Functions:  Filters/cleanses blood of foreign substances  Destroy worn-out blood cells  Recycles components of worn out blood cells (i.e. hemoglobin)  Stores platelets  Protect body during hemorrhage

 Lymphoid mass found in throat  Function: Programs lymphocytes with the help of thymosin (hormone)

 Small, lymphoid tissue in back of throat  Function: Capture and remove any foreign pathogens(substan ces)  Reason they become swollen during colds/viruses

 Location: Wall of small intestine  Function: Capture and destroy bacteria  Prevent foreign pathogens from penetrating intestinal wall

 The body is constantly in contact with bacteria, fungi, and viruses  The body has two defense systems for foreign materials  Innate (nonspecific) defense system Attacks ANY foreign pathogen  Adaptive (specific) defense system Attacks SPECIFIC substances  Immunity—specific resistance to disease  -Immun=free

 AKA “non-specific defense system”  Innate body defenses are mechanical barriers to pathogens such as  Body surface coverings Intact skin Mucous membranes Line all body cavities that are exposed (i.e. digestive, respiratory, urinary, and reproductive tracts)  Specialized human cells  Chemicals produced by the body

 Skin and mucous membranes  Physical barrier to foreign materials  Also provide protective secretions pH of the skin is acidic to inhibit bacterial growth Sebum is toxic to bacteria Stomach releases hydrochloric acid to kill pathogens Saliva and lacrimal fluid contain lysozymes which kill bacteria Mucus traps microorganisms and prevent them from entering the digestive or respiratory tract

 Phagocytes  I.e. macrophage or neutrophil  Swallows foreign pathogen  Natural killer cells  Kill cancer and virus cells  Fight off these pathogens by detecting sugar molecules on pathogen’s surface

 Inflammatory response  Happens when tissue is injured  4 signs: Redness, heat, inflammation, swelling pain  Histamine & Kinins causes: Vessels to dilate causing inflammation Activate pain receptors to alert body of problem Attract WBCs and phagocytes to clean cellular debris from tissue damage

 Antimicrobial proteins  Help fight pathogens by attacking them or inhibiting their progress through the use of? Complement proteins Bind to sugar receptors on pathogen’s cell and causes holes which allow water to enter the cell and cause it to burst Interferon: Bind to viruses’ cells and cause proliferation of interferon molecules which hinder the viruses’ cell replication

 Fever  Effects of fever include: Prohibiting iron or zinc availability which bacteria require to multiply Increases metabolic rate which in turn increases the repair process HIGH fevers can denature proteins and enzymes causing breakdowns within the body

 Immune response is the immune system’s response to a threat  Provides protection by the use of antigens through specificity  Immunology is the study of immunity  Antibodies are proteins that protect from pathogens

 When the body is exposed to a pathogen it builds “antibodies”  Less likely the body will acquire that same pathogen again  Immune response becomes stronger when faced with this invading pathogen in the future  3 steps involved in immune response:  1. Antigen specific: It attacks particular pathogens/foreign substances  2. Systemic: Immunity is not confined to only the “initial infection site.” Can work through the circulatory system  3. Memory: Has stronger attacks against previously fought pathogens

 Humoral Immunity/Antibody-mediated immunity  Antibodies fight off infection in the blood stream (humors/fluids)  Cellular Immunity/Cell-mediated immunity  Fights off viral cells, cancer cells, and foreign graft cells either directly or indirectly

 Antigen:  Any substance responsible for initiating an immune response  Examples of common antigens Foreign proteins (strongest) Nucleic acids Large carbohydrates Some lipids Pollen grains Microorganisms

 Self-antigens  Human cells have many surface proteins  Our immune cells do not attack our own proteins because they are recognizable in our bodies  Our cells in another person’s body can trigger an immune response because they are foreign Restricts donors for transplants Unless…medications are taken to suppress immune system  Hapten/Incomplete Antigen:  A small molecule antigen that cannot initiate the creation of antibodies  Instead, it binds with our proteins  The body doesn’t not recognize combination and attacks it  Examples:  Poison ivy, detergents, hair dyes, etc

 B lymphocytes/B-cells  Create antibodies and direct humoral immunity  T lymphocytes/T-cells  These cells do not produce antibodies  Mature T-cells are the most effective in fighting off foreign antigens

 Immunocompetent—cell becomes capable of responding to a specific antigen by binding to it  Cells of the adaptive defense system  Lymphocytes Originate from hemocytoblasts in the red bone marrow B lymphocytes become immunocompetent in the bone marrow (remember B for B one marrow) T lymphocytes become immunocompetent in the thymus (remember T for T hymus)

 Cells of the adaptive defense system (continued)  Macrophages Arise from monocytes found in bone marrow Become widely distributed in lymphoid organs Secrete cytokines (proteins important in the immune response) Tend to remain fixed in the lymphoid organs Unlike lymphocytes that circulate

 B lymphocytes with specific receptors bind to a specific antigen  The binding event activates the lymphocyte to undergo clonal selection  Lymphocyte grows and multiplies  Most B cells turn into plasma cells  The remaining B cells are stored as memory cells for future encounters with that antigen

 Secondary humoral responses  Memory cells are long-lived  A second exposure causes a rapid response  The secondary response is stronger and longer lasting

 Occurs when B cells encounter antigens and produce antibodies  Active immunity can be  Naturally acquired during bacterial and viral infections  Artificially acquired from vaccines

 Occurs when antibodies are obtained from someone else  Acquired naturally from a mother to her fetus (naturally acquired) when passing through placenta  Conferred artificially from immune serum or gamma globulin (artificially acquired) Shots given after exposure to certain pathogens  Immunological memory does not occur  Protection provided by “borrowed antibodies”  Lasts 2-3 weeks

 Secreted by activated B cells  Respond to a specific antigen

 Antibody classes  Antibodies of each class have slightly different roles  Five major immunoglobulin classes (MADGE) IgM—can fix complement IgA—found mainly in mucus IgD—important in activation of B cell IgG—can cross the placental barrier and fix complement IgE—involved in allergies

 Antibody function  Antibodies inactivate antigens in a number of ways Complement fixation Causes lysis of the cell Neutralization Bind to bacterial cells to block the release of that cell’s toxic chemicals Agglutination Clumping of foreign cells Precipitation When antigen-antibodies combine forming large complexes that settle out a solution that was agglutinated

 Antigens must be presented by macrophages to an immunocompetent T cell  T cells must recognize nonself and self (double recognition)  After antigen binding, clones form as with B cells, but different classes of cells are produced  Cytotoxic (killer T cells): Attack virus infected, cancer, or foreign graft cells  Helper T cells: Directors of immune system Recruit other cells to fight pathogens  Regulatory T cells: Stop the immune response once antigen is destroyed

 Major types of grafts  Autografts—tissue transplanted from one site to another on the same person  Isografts—tissue grafts from an identical person (identical twin)  Allografts—tissue taken from an unrelated person  Xenografts—tissue taken from a different animal species

 Autografts and isografts are ideal donors  Xenografts are never successful  Allografts are more successful with a closer tissue match

 Abnormal, vigorous immune responses  Types of allergies  Immediate hypersensitivity Triggered by release of histamine from IgE binding to mast cells Causes dilation of small blood vessels Leads to: itchy, watery, runny nose/eyes Reactions begin within seconds of contact with allergen Anaphylactic shock—dangerous, systemic response Throat closes in response to allergy, blocking airway

 Production or function of immune cells or complement is abnormal  May be congenital or acquired  Includes AIDS (Acquired Immune Deficiency Syndrome)  Kills of Helper T-cells  Includes Severe Combined Immunodeficiency Disease (SCID)  Congenital condition  The immune system does not distinguish between self and nonself  The body produces antibodies and sensitized T lymphocytes that attack its own tissues