the lymphatic and immune system

• definitions

  • Antibody – specialized protein that destroys specific antigen
  • Antigen - foreign substance in the body
  • Inflammation – body’s response to tissue damage
  • Lymphocyte – type of WBC involved in immunity e.g, B cells and T cells
  • Macrophage - scavenger cells that engulfs and destroys microbes
  • Metastasis – spread of cancer form its site of origin
  • Microbe – microorganisms e.g., bacteria, fungus, virus, protozoa
  • Pathogen - disease-causing microorganism
  • Phagocyte – a cell that engulfs or digest microbes which includes macrophages and some types of WBC
• function of the lymphatic system

  • It transports clear, straw-coloured fluid from interstitial spaces surrounding cells to the blood
  • Includes drainage of interstitial fluid, transportation of dietary lipids and protection against invasion.
• What does the term "lymph" refer to?


  Clear water derived from interstitial fluid containing proteins, lipids, foreign particles, and cell debris
• What components are found in lymph?


  Proteins, lipids, foreign particles, cell debris, and lymphocytes
• What are lymphatic capillaries?


  Close-ended vessels with a larger diameter than blood vessels
• Where are lymphatic capillaries found in the body?


  Throughout the body except in the central nervous system, splenic pulp, and bone marrow
• What is the function of lymphatic vessels, trunks, and ducts?


  To carry lymph from lymphatic capillaries through lymph nodes to larger vessels
• What is the role of lymph nodes?


  To filter lymph before it returns to the bloodstream and produce lymphocytes
• Where is the thymus gland located?


  In the mediastinum behind the sternum and between the lungs
• What hormone does the thymus gland produce?


  Thymosin hormone for the development of T cells
• What is the largest single mass of lymphatic tissue in the body?


  The spleen
• What are the functions of the spleen?


  Filters and stores platelets and blood, and produces lymphocytes
• What are lymphatic nodules?


  Mucosa-associated lymphoid tissue positioned to protect the body from pathogens
• Where are lymphatic nodules found?


  In the GI tract, respiratory airways, urinary tract, reproductive tract, tonsils, Peyer’s patches, and appendix
• What are the key components of the lymphatic system?


  • Lymph
  • Lymphatic capillaries
  • Lymphatic vessels, trunks, and ducts
  • Lymph nodes
  • Lymphatic organs (thymus and spleen)
  • Lymphatic nodules
• mechanical barriers to disease

  • The skin
  • mucous membranes – traps microbes and moves it away from vital areas
  • Lacrimal apparatus – produces tears to wash away microbes and dirt
  • Saliva
  • Urination, defecation and vomiting
• chemical barriers to disease

  • Sebum
  • Perspiration
  • Gastric juices e.g., hydrochloric acid
  • Vaginal secretions
  • Natural killer cells (NK cells) – type of lymphocytes that can kill variety of microbes as well as tumour cells; found in spleen, red bone marrows, lymph nodes and blood.
  • Phagocytes – type of lymphocytes that ingest or eat microbes. 2 main types of phagocytes: 1. Neutrophils – type of WBC, 2. Macrophages – scavenging cells found in the skin, liver, lungs, nervous system, spleen, lymph nodes, and red bone marrow
• inflammation


  is the body’s response to all types of injuries, and it serves to prevent the spread of further damage. Key signs are swelling, heat, redness, pain and loss of function of affected area
• fever


   abnormally high body temperature and body’s normal way of dealing with infection caused by toxins released by microbes. Increase in temperature intensifies the effects of body’s own antimicrobial substances, inhibits microbial growth and increases the growth of tissue repair
• Immune response or immunity


  main difference between immunity and nonspecific resistance to disease:

  1. Immunity involves very focused recognition and response to foreign molecules called ‘antigen’ (e.g., microbes, bacteria, viruses, fungus, pollen, egg white, transplanted tissues and organs.
  2. Immunity involves ‘memory’
• lymphocytes


  also called 'immunocompetent cells' which responds directly to antigens

  2 types of lymphocytes:

  1. B cells - matures in red bone marrow, develop into plasma cells and secretes antibodies
  2. T cells - develop in red bone marrow and migrate to thymus glands to mature, T cells develop antigen receptors. There are 2 types of T cells:
  3. CD4+ cells
  4. CD8+ cells
• 2 types of immune response

  1. Cell-mediated (cellular) immune response or CMI –’cells attack cells’ e.g., CD8+ T cells reproduce into killer cells which leave lymphatic tissues to seek out and destroy antigens (fungi, parasites, viruses and some cancer cells)
  2. Antibody-mediated (humoral) immune response or AMI – antibodies bind to antigens and inactivate them e.g.; B cells develop into plasma cells which secrete antibodies which binds onto antigen and destroy it. Common response to body fluids and pathogens such as bacteria that have multiplied in body fluids
• common pathologies of the lymphatic and immune system

  • Red flags:
  • Chronic fever of unknown origin
  • Recurring fever with night sweats and weight loss
  • Anaphylaxis - severe allergic reactions
  • Allergy - hypersensitivity or overreaction to substances (allergen) normally harmless to common people
  • Lymphadenitis
  • Lymphedema
  • Cancer of the lymphatic system - leukemia, lymphomas (Hodgkin’s and Non-Hodgkin’s lymphoma)
  • Metastasis
  • Infectious diseases - AIDS, glandular fever (infectious mononucleosis), tonsillitis
  • Autoimmune disease and disorders - SLE or systemic lupus erythematosus