• Consists of extensive network of lymph vessels and nodes through which lymph circulates
  • Defends the body against harmful external agents like bacteria, virus, etc.
  • A drainage system (coarse) accessory to venous system (fine)
  • The tissue fluid formed at arterial end of capillaries is absorbed back into the blood, the remaining is absorbed by lymph capillaries
  • Functions- drain excess tissue fluid to the venous system, absorb fat from intestine and transport to blood, immunological defence


  • Lymph
  • Lymph capillaries
  • Lymph vessels
  • Lymphoid organs
  • Epithelio lymphoid system
  • Bone marrow

  • Lymph capillaries- numerous in skin, glands, mucous and serous membranes…… absent at epidermis, hair, nail, cornea, articular cartilage, bone marrow
  • Lymph vessels- superficial & deep
  • Lymph ducts- thoracic duct and right lymphatic duct

Lymphoid organs

  • Lymphatic tissue is Made up of framework of reticular fibres , lymphocytes and related plasma cells & macrophages
  • Circumscribed concentration of lymphatic tissue is c/a lymph nodule
  • Has germinal centers
  • Two types- primary , involved in production of lymphocytes & secondary, involved in activation of lympho and initiation of immune response

  • Lymph node
  • Spleen
  • Thymus

Epithelio lymphoid system

  • Mucosa associated lymphatic tissue(MALT)
  • Tonsil
  • Payer’s patches
  • Abdominal tonsil

Reticulo endothelial system

  • Concerned with phagocytosis
  • Imp for general and local defense
  • Macophages
  • Monocytes
  • Pericytes
  • Dust cells
  • Reticular cells
  • Kupffer cells
  • Microglia

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