Chapter 14: Lymphatic System and Immunity

• Functions of the Lymphatic System

  Fluid balance

  Fat Absorption

  Defense
• Components of the Lymphatic System

  Lymph

  Lymphocytes

  Lymphatic vessels

  Lymph nodes

  Tonsils

  Spleen

  Thymus Gland
• Lymphatic Capillaries


  Carries fluid in one direction from tissues to circulatory system; Fluid moves from blood capillaries into tissue spaces

  tiny, closed-ended vessels

  fluid moves easily into capillaries

  in most tissues

  join to form lymphatic vessels
• Lymphatic vessels


  resemble small veins; where lymphatic capillaries join; One-way valves
• Right lymphatic duct


  where lymphatic vessels from right upper limb and right head, neck, chest empty; empties into right subclavian vein
• Thoracic duct


  collects lymph from the from remaining lymphatic vessels which do not enter the right lymphatic duct.; empties into left subclavian vein
• Lymph


  fluid that enters lymphatic capillaries composed of water and some solutes
• Tonsils


  form a protective ring of lymphatic tissue around nasal and oral cavities
• palatine tonsils on each side of oral cavity
• pharyngeal tonsils near internal opening of nasal cavity
• lingual tonsils posterior surface of tongue
• Lymph Nodes


  rounded structures that vary in size

  located near lymphatic vessels

  groin, armpit, neck

  lymph passes through lymph nodes before entering blood
• Lymph


  moves through and immune system

  Is activated (lymphocytes produced) if foreign substances are detected

  Removes microbes by macrophages
• Spleen


  size of clenched fist

  located in abdomen

  filters blood

  detects and responds to foreign substances

  destroys old red blood cells

  serves as a blood reservoir
• white pulp


  lymphatic tissue surrounding arteries
• red pulp


  contains macrophages and red blood cells that connect to veins
• Thymus Gland


  bilobed gland

  located in mediastinum behind the sternum

  stops growing at age 1

  at age 60 decreases in size

  produces and matures lymphocytes
• Immunity


  is the ability to resist damage from foreign substances.

  Immunity can protect against microbes, toxins, and cancer cells.
• Innate Immunity


  present at birth

  defense against any pathogen

  accomplished by physical barriers, chemical mediators, cells, inflammatory response
• Physical Barriers


  First line of defense

  Skin and mucous membranes act as barriers to pathogens and toxins

  Tears, saliva, urine wash away pathogens and toxins
• Chemical Mediators


  are chemicals that can kill microbes and prevent their entry into cells
• Lysozyme


  found in tears and saliva to kill bacteria
• Mucous membranes


  prevent entry of microbes
• Histamine


  promote inflammation by causing vasodilation
• Interferons


  proteins that protect against viral infections by stimulating surrounding cells to produce antiviral proteins
• White blood cells


  produced in red bone marrow and lymphatic tissues fight foreign substances
• Phagocytic cells


  ingest and destroy foreign substances

  Example—neutrophils and macrophages
• Neutrophils


  first to respond to infection but die quickly
• Eosinophils


  produced in red bone marrow

  release chemicals to reduce inflammation
• Basophils


  made in red bone marrow

  leave blood and enter infected tissues

  can release histamine
• Macrophages


  initially were monocytes

  leave blood and enter tissues

  can ingest more than neutrophils

  protect lymph in lymph nodes and blood in spleen and liver

  given specific names for certain areas of body (Kupffer cells in liver)
• Mast cells


  made in red bone marrow

  found in skin, lungs, gastrointestinal tract, urogenital tract

  can release leukotrienes
• Natural Killer Cells


  type of lymphocyte

  produce in red bone marrow

  recognize classes of cells such as tumor cells or virus infected cells

  release chemicals which lyse cells
• Inflammatory Response


  involves chemicals and cells produced due to injury

  signaled by presence of foreign substance

  stimulates release of chemical mediators
• Adaptive Immunity


  defense that involves specific recognition to a specific antigen

  acquired after birth

  reacts when innate defenses don’t work

  slower than innate immunity

  has memory

  uses lymphocytes (B and T cells)

  2 types antibody-mediated and cell-mediated
• Antigen


  substance that stimulates an immune response

  Example—bacteria, virus, pollen, food, drugs
• Self-antigen


  molecule produced by the person’s body that stimulates an immune system response
• Antibody


  proteins the body produces in response to an antigen
• Stem cells


  Live in red bone marrow

  give rise to all blood cells

  give rise to some pre-T cells and pre-B cells
• Lymphocytes


  type of white blood cell

  involved in adaptive immunity

  develop from stem cells

  differentiate into specific lymphocytes such as B or T cells