in Lymphatic System and Immune System by

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The lymphatic system consists of lymph, lymphatic capillaries, lymphatic vessels, lymph nodes and lymphatic organs.

1. Lymph:

  1. It is the interstitial fluid (tissue fluid) present between the cells of a tissue.
  2. It is colourless or yellowish fluid present in the lymph vessels.
  3. It is composed of 94% water and 6% solids.
  4. Lymph=Blood – [RBCs + Plasma proteins + platelets]

2. Lymphatic capillaries:

  1. Small, thin walled vessels lined by endothelium resting on a basement membrane.
  2. They are present throughout the body except spinal cord, brain, internal ear, bone marrow, eye ball.

3. Lymphatic vessels or ducts:

  1. Formed by joining of lymphatic capillaries.
  2. Numerous, present in various part of the body.
  3. Made up of three layer – Tunica externa, tunica media and tunica interna.
  4. Two main types of lymphatic ducts:

a. Right lymphatic duct:

  • Smallest lymphatic duct. (length approximately 1.25 cm)
  • Collects lymph from upper right side of the body.
  • Carries lymph to the right sub-clavian vein.

b. Thoracic duct (Left lymphatic duct):

  • Longest lymphatic duct (length approximately 38-45 cm).
  • Carries lymph to the left sub-clavian vein.
  • Collects lymph from the left part of head, neck, thoracic cavity and left arms.

4. Lymph nodes (Lymph Glands):

  1. Masses of lymphatic tissue and connective tissue.
  2. Small, oval bean-like structures.
  3. Present in the neck axilla, thorax, abdomen and groin region.

5. Lymphatic organs:

  1. Primary lymphatic organs → Red bone marrow and Thymus
  2. Secondary lymphatic organs → Spleen (Largest component of lymphatic system) and Tonsils.