Lymphatic System

• Lymph


  A transparent, usually slightly yellow, often opalescent liquid found within the lymphatic vessels, and collected from tissues in all parts of the body and returned to the blood via the lymphatic system
• Components of lymph


  • Lymph-fluid resembling plasma
  • Lymphatic vessels
  • Lymphoid organs

  
• Functions of the lymphatic system

  • Production, maintenance and distribution of lymphocytes
  • The return of fluid and solutes from the peripheral tissues to the blood
  • The distribution of hormones, nutrients and waste products from their tissues of origin to general circulation

  
• Components of the lymphatic system

  • A network of vessels, cells, organs, and glands that produce and transport body fluids
  • Lymphatic vessels collect and carry away excess fluid from interstitial spaces
  • The organs of the lymphatic system help defend against disease
  • Lymphatic capillaries originate as lymph capillaries-are tiny, closed-ended tubes that extend into interstitial spaces
  • Lymph is the fluid that is received through the thin walls of lymphatic capillaries
  • The walls of lymphatic vessels are like veins but with thinner walls
  • Larger lymphatic vessels pass through lymph nodes and merge to form lymphatic trunks

  
• Main channels of the lymphatic system

  • Right lymphatic duct
  • Thoracic duct

  
• Lymphatic trunks and collecting ducts

  • Drain lymph from the body and are named for the regions they drain
  • These trunks join one of two collecting ducts - either the thoracic duct or right lymphatic duct
  • The fluid is eventually returned to the subclavian vein

  
• Types of lymphatic tissue

  • Diffuse lymphatic tissue
  • Discrete-Lymphatic nodules
  • Lymphatic organs

  
• Diffuse lymphatic tissue


  No capsule present, found in connective tissue of almost all organs
• Discrete-Lymphatic nodules


  No capsule present, oval-shaped masses of lymphatic cells, found singly or in clusters in lamina propria of mucous membranes, example peyers patch and tonsils
• Lymphatic organs


  Capsule present, examples are lymph nodes, spleen, thymus gland

  
• Bone marrow


  • Immature T cells (pre-T cells) migrate from red bone marrow to the cortex of the thymus, where they proliferate and begin to mature
  • Pluripotent stem cells in red bone marrow give rise to mature, immunocompetent B cells and to pre-T cells
• Spleen


  • Largest lymphatic organ 5 inches long, 160 grams
  • Located between the stomach & diaphragm
  • Lies along the curving lateral border of the stomach between the 9th & 11th ribs
  • Structure is similar to a node but no afferent vessels or sinuses
  • Red pulp contains all the components of circulating blood
  • White pulp is similar to lymphatic nodules
  • Functions are to filter blood, store blood, and initiate immune response

  
• Thymus gland


  • Location - posterior to the sternum in the mediastinum
  • Soft, bi-lobed organ
  • The capsule divides it into 2 lobes
  • Infant - conspicuous, Puberty - maximum size, Maturity - decreases in size (involution)
  • Function is differentiation and maturation of T cells

  
• Mucosa-associated lymphoid tissue (MALT)


  A diffuse system of small concentrations of lymphoid tissue found in various submucosal membrane sites of the body, such as the gastrointestinal tract, oral passage, nasopharyngeal tract, thyroid, breast, lung, salivary glands, eye, and skin

  
• Types of MALT


  • Tonsils
  • Appendix
  • Small Intestinal area

  
• Functions of the lymphatic system


  • Drains excess interstitial fluid
  • Transports dietary lipids
  • Carries out immune responses
• Immunity


  The quality or state of being able to resist a particular disease especially through preventing development of a pathogenic microorganism or by counteracting the effects of its products
• Types of immunity


  • Natural active immunity
  • Artificial active immunity
  • Natural passive immunity
  • Artificial passive immunity
• Natural active immunity


  Production of one's own antibodies or T cells as a result of infection or natural exposure to antigen
• Artificial active immunity


  Production of one's own antibodies or T cells as a result of vaccination
• Natural passive immunity


  Temporary, fetus acquires antibodies from mother through the placenta before birth and through milk after birth
• Artificial passive immunity


  Temporary, injection of immune serum (antibodies or lymphocytes)
• Immune response


  • The reaction of the cells and fluids of the body to the presence of a substance which is not recognized as a constituent of the body itself
• Steps of immune response

  1. Helper T cells are activated when phagocytes display antigens on their surface

  2. Activated Helper T cells divide and activate other cells (killer T cells and B cells)

  3. Killer T cells attack infected body cells and kill them

  4. B cells produce antibodies that mark pathogens for destruction
• Cells of the immune system

  • T cells
  • B cells
  • Plasma cells
  • Lymphocytes
  • Antibodies
• Immune Response

  The reaction of the cells and fluids of the body to the presence of a substance which is not recognized as a constituent of the body itself
• Immune Response Steps

  1. Helper T cells display antigens on their surface

  2. Helper T cells that recognize the specific antigen are activated

  3. Activated Helper T cells divide and activate other cells (killer T cells and B cells)
• Killer T cells

  • They attack infected body cells and kill them
• Killer T cells

  • They release enzymes directly into pathogens causing them to lyse and die
• 1. cells


  Lymphocytes that produce antibodies
• Plasma Cells


  Cells that produce antibodies
• Lymphocyte

  A type of white blood cell that plays a central role in cell-mediated immunity
• Antibodies


  Proteins produced by B cells that bind to and neutralize pathogens, making them easier to attack and engulf
• T cell


  A type of lymphocyte that plays a central role in cell-mediated immunity
• T cells


  • They have a T-cell receptor on the cell surface
• T cell formation

  1. Precursors of T cells are formed in the bone marrow

  2. They migrate to the thymus where they mature
• Helper T cells


  They activate B cells and killer T cells
• Effector T cells


  • They actively respond to a stimulus, such as co-stimulation
• T helper cells

  They assist other white blood cells in immunologic processes, including maturation of B cells and activation of cytotoxic T cells and macrophages
• T helper cells


  • They express the CD4 glycoprotein on their surfaces