Chapter 19: The Lymphatic System

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Chapter 19The Lymphatic System

• Structure and function
• Lymphatic organs and tissues

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Components of the lymph system

• Lymphatic vessels
• Lymph organs
• Lymphatic tissuespecialized reticular connective
  tissue with lymphocytes
• Red bone marrow
• Lymph (clear fluid)
• Blood plasma?interstitial fluid?lymph

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Lymphatic system functions

• Return excess interstitial fluid and leaked
  proteins to blood
• Lacteals transport dietary lipids (chyle)
• Vitamins A, D, E and K from GI tract
• Carry out immune responses
• Cell mediated immune responsesT cells destroy
  intruders with cytotoxic substances.
• Antibody-mediated immune responses detect and
  destroy specific foreign substances.

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Lymphatic vessels

• Lymphatic capillaries resemble veins but have
  thinner walls and more valves.
• Lymph vessels in the skin follow veins.
• Lymph vessels in the viscera follow arteries.
• Lymph vessels are NOT found in avascular tissue,
  CNS, parts of spleen and red bone marrow.

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Lymphatic capillaries

• Interstitial fluid moves in but not out
• Lymph capillaries?lymph vessels ? lymph trunks ?
  thoracic and right lymphatic duct

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Flow of lymph

• Blood capillaries (blood) ? interstitial spaces ?
  lymph capillaries ? lymph vessels ? lymph trunks
  ? thoracic and right lymphatic duct ? junction of
  the internal and subclavian veins (blood).
• Smooth muscles in lymph vessels contract
  rhythmically
• Pulsations in adjacent arteries aid flow
• Skeletal muscle and respiratory pump

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Lymph flow
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Lymphoid organs
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Lymphoid cells

• Lymphocytes
• Macrophages
• Dendritic cells
• Reticular cells

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Lymphoid tissue

• Site for lymphocyte residence and proliferation
• Provides sentinel position for lymphocytes and
  macrophages
• Lymphocytes cycle among lymphoid tissue, blood
  circulation and loose connective tissue.
• Can be diffuse or densely organized

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Lymph nodes

• Filter lymph
• Activate the immune system

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Spleen

• Removes aged and defective RBCs
• Stores breakdown products of RBCs
• Erythrocyte production in fetus
• Stores blood platelets

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Spleen

• White pulpB and T cells carry out immune
  function.
• Red pulpfunctions concerning RBCs

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Thymus

• Secretes thymopoietin, thmosins to make T-cells
  immunocompetent
• Bilobed organ
• Trabeculae divide lobe into lobules.
• Thymic corpuscles

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Thymic medulla

• The medulla consists of more mature T cells,
  epithelial cells, dendritic cells and maphages.
• Thymic corpuscles.
• Atrophy of thymus.

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Tonsils
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MALT

• Mucosa-associated lymphatic tissue