Lymphatic system

• The lymphatic system: A network of vessels that transports lymph, a clear fluid containing white blood cells, from the tissues to the blood.

  A) Cervical

  B) Thoracic duct

  C) Thymus

  D) Axillary

  E) Spleen

  F) Upper limb

  G) Inguinal

  H) Lower limb

  I) Pelvic

  J) Lumbar

  K) Cisterna chyli

  L) Mammary gland

  
• The lymphatic system is a series of vessels and nodes that collect and filter excess tissue fluid (lymph), before returning it to the venous circulation. It forms a vital part of the body’s immune defence.
• There are a number of organs that contain lymphatic tissue. They are involved in blood filtering and the maturation of lymphocytes.

  ·       Spleen –  Functions mainly as a blood filter, removing old red blood cells. It also plays a role in the immune response.

  ·       Thymus – Responsible for the development and maturation of T lymphocyte cells.

  ·       Red bone marrow – Responsible for maturation of immature lymphocytes, much like the thymus.

  ·       In addition, some lymphatic tissue is located in the tonsils, appendix, and in the walls of the gastrointestinal tract.
• Lymph nodes are exposed to the fluid as it passes through the node, and can mount an immune response if they detect the presence of a pathogen. This immune response often recruits more inflammatory cells into the node – which is why lymph nodes are palpable during infection.
• Lymph fluid enters the node through afferent lymphatic channels and leaves the node via efferent channels.
• Macrophages located within the sinuses of the lymph node act to filter foreign particles out of the fluid as it travels through.
• The right lymphatic duct is responsible for draining the lymph from the upper right quadrant of the body. This includes the right side of the head and neck, the right side of the thorax and the right upper limb. The thoracic duct is much larger and drains lymph from the rest of the body. These two ducts then empty into the venous circulation at the subclavian veins, via the right and left venous angles.

  A) Right lymphatic duct

  B) Right lymphatic duct

  C) Thoracic duct drains into subclavian vein

  D) Thoracic duct

  E) Cisterna chyli of thoracic duct

  F) Drained by thoracic duct

  
• Lymph is a transudative fluid that is transparent and yellow. It is formed when fluid leaves the capillary bed in tissues due to hydrostatic pressure. Roughly 10% of blood volume becomes lymph. The majority of the volume (around 95%) comprised of water and the remaining 5% is composed of proteins, lipids, carbohydrates (mainly glucose), various ions and some cells (mainly lymphocytes), although this can vary depending on where in the body the lymph is produced. For example, chyle (lymph that is produced in the gastrointestinal system) is particularly rich in fats.