Lymphatic system notes

• Lymphatic System


  Network of lymphatic pathways that transport lymph
• Lymph


  • Aids in immune function
  • Flows only toward the heart
• Lymph nodes


  • Dense lymphoid tissue
  • Contain phagocytic cells and lymphocytes
• Lymphoid organs


  • Produce and store lymphocytes
• Lymphatic capillaries


  1. Blind-ended vessels

  2. Lie between cells and blood capillaries

  3. Allow uptake of larger particles

  4. Route for pathogens or cancer cells

  5. Increased permeability
• Lymphatic capillaries


  • One-way microvalves of overlapping endothelial cells
• Lacteals


  • Specialized lymph capillaries in intestinal villi
  • Absorb digested fat
  • Deliver fatty lymph (chyle) to blood
• Collecting lymphatic vessels


  • Larger lymphatic vessels
  • Structured with tunics like veins
  • Thinner walls
  • More internal valves
  • Anastomose more frequently
• Lymph drainage


  1. Lymph capillaries drain to collecting lymphatic vessels

  2. Collecting vessels in skin travel with superficial veins

  3. Deep lymphatic vessels travel with arteries
• Lymphatic trunks


  Larger lymphatic vessels
• Bone marrow


  The spongy tissue inside bones where all blood cells, including lymphocytes, are produced.
• Thymus


  A small organ in the chest where T cells develop and mature.
• Spleen


  A large organ located in the abdomen that filters the blood, removes waste products, and stores lymphocytes.
• Lymph nodes


  Small, bean-shaped glands found throughout the body that filter lymph fluid, trap pathogens, and produce and store lymphocytes.
• Tonsils


  Two masses of lymphoid tissue located at the back of the throat that help to filter out bacteria and viruses that enter the body through the mouth and nose.
• Peyer's patches


  Clusters of lymphoid tissue found in the walls of the small intestine that help to protect the body against infections that enter through the digestive tract.
• Lymphocytes


  A type of white blood cell produced in the bone marrow that plays a crucial role in the body's defense against infection and disease.
• B cells


  A type of lymphocyte produced in the bone marrow that is responsible for producing antibodies, which help to neutralize or destroy pathogens such as viruses and bacteria.
• T cells


  A type of lymphocyte produced in the bone marrow that is involved in cell-mediated immunity, which means they directly attack and destroy infected cells in the body.
• Blind-ended vessels


  Lymphatic capillaries are tiny vessels that are blind-ended, meaning they do not have a distinct beginning or end. They are formed by a simple squamous epithelium, also known as endothelium, which is a thin layer of cells that lines the inside of the capillary.
• Interstitial fluid


  Lymphatic capillaries are responsible for collecting excess interstitial fluid, which contains proteins, waste products, and other substances that cannot be reabsorbed by the blood capillaries.
• Primary valves


  Lymphatic capillaries have openings, or "primary valves," that are larger than the size of blood capillary pores, which allow for the uptake of larger particles, such as proteins and cellular debris.
• Pathogens or cancer cells

  Lymphatic capillaries serve as a route for pathogens, such as bacteria and viruses, and cancer cells to enter the lymphatic system. Once inside the lymphatic system, these cells can be transported to the lymph nodes, where they may be filtered out and destroyed by the immune system.
• Flap valves


  Lymphatic capillaries have increased permeability compared to blood capillaries, which allows for the efficient uptake of interstitial fluid and other substances. This increased permeability is due to the presence of "flap valves" that allow for the one-way flow of fluid into the lymphatic capillary.
• Larger lymphatic vessels


  Main conduits for lymphatic fluid; structurally similar to veins with three tunics in their walls; thinner walls and more internal valves than veins
• Smaller lymphatic vessels

  Smaller, more numerous vessels that collect lymphatic fluid from the tissues; thinner walls than larger lymphatic vessels; fewer internal valves than larger lymphatic vessels
• Largest lymphoid organ
• Muc-Red Lymphoid The MALD
• 36 Mucosa-Associated Lymphoid Tissue (MALT)
• Peyer's patche
• Lymphatic System


  • Network of lymphatic vessels (lymphatics)
  • Lymph: fluid in vessels
  • Lymph nodes: cleanse lymph
• Lymphatic System


  • Returns interstitial fluid to blood
  • Lymphoid organs and tissues are the structural basis of immune system
  • House phagocytic cells and lymphocytes
• Lymphatic Vessels


  1. Lymph flows only toward heart

  2. Lymphatic capillaries

  3. Larger lymphatic vessels: collecting vessels, lymphatic trunks, lymphatic ducts
• Lymphatic Capillaries


  • Blind-ended vessels
  • Weave between tissue cells and blood capillaries
  • Absent from bones, teeth, and bone marrow
  • More permeable than blood capillaries
  • Can take up larger particles
  • Route for pathogens or cancer cells to travel throughout body
  • Increased permeability due to one-way minivalves of overlapping endothelial cells and increases in ECF volume
• Lacteals


  • Specialized lymph capillaries present in intestinal mucosa
  • Absorb digested fat
  • Deliver fatty lymph (chyle) to blood
• Collecting Vessels


  • Larger lymphatic vessels structured with tunics like veins
  • Have thinner walls
  • More internal valves
  • Anastomose more frequently
  • Lymph capillaries drain to collecting lymphatic vessels
  • Collecting vessels in skin travel with superficial veins
  • Deep lymphatic vessels travel with arteries
• Lymphatic Trunks


  • Union of largest collecting vessels
  • Drain large areas of body
• Lymphatic Ducts


  • Right lymphatic duct drains right upper arm and right side of head and thorax
  • Thoracic duct drains rest of body
  • Empty lymph into venous circulation at junction of internal jugular and subclavian veins
• Lymph Transport


  • Low-pressure system like venous system
  • Lymph is propelled by mechanisms similar to veins: milking action of skeletal muscle, pressure changes in thorax during breathing, valves to prevent backflow, pulsations of nearby arteries, contractions of smooth muscle in walls of lymphatics
• Lymphedema


  Severe localized edema caused by anything that prevents normal return of lymph to blood