CH 20 Lymph Node Anatomy

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CH 20Lymph Node Anatomy
James F. Thompson, Ph.D.
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The Lymph Nodes

• Anatomy
• oval, bean shaped structures scattered throughout
  body along lymph vessels
• may be deep or superficial
• concentrated along the respiratory tree and GI
  tract, in the mammary glands, axillae, and groin
• filter lymph fluid to trap foreign organisms,
  cell debris, and tumor cells

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Lymphatic Organs Lymph Nodes

• Covered by a fibrous connective tissue capsule
• Trabeculae extend from cortex to medulla
• Stroma the internal supportive connective
  tissue network of reticular fibers

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Structure of a Lymph Node

• outer cortex - filled with lymph follicles
• outer edge of follicle contains more T cells
• inner germinal center is the site of B-cell
  proliferation
• inner medulla - medullary cords of lymphocytes,
  macrophages, plasma cells (activated B cells)

Cortex
Medulla
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Structure of a Lymph Node

• Medullary cords extend from the cortex and
  contain B cells, T cells, and plasma cells
• Throughout the node are lymph sinuses
  crisscrossed by reticular fibers
• Macrophages reside on these fibers where they
  phagocytize foreign matter

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Histology of Lymph Nodes
follicles with germinal centers
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Circulation in the Lymph Nodes

• Lymph enters via a number of afferent lymphatic
  vessels
• It then enters a large subcapsular sinus and
  travels into a number of smaller sinuses
• It meanders through these sinuses and exits the
  node at the hilus via efferent vessels
• The node acts as a settling tank, because there
  are fewer efferent vessels, lymph stagnates
  somewhat in the node
• This allows lymphocytes and macrophages time to
  carry out their protective functions

Only lymph nodes filter lymph!
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Lymph Flow Through Lymph Nodes

• fluid enters cortex through afferent vessels
• filter and trap damaged cells, microorganisms,
  foreign substances, tumor cells by reticular
  fibers
• macrophages phagocytize some, lymphocytes destroy
  some by immune defenses
• exits medulla by efferent vessels at hilus

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Blood Flow Through Lymph Nodes

• blood vessels enter and exit at the hilus
• this blood circulation provides nutrition for the
  nodes tissues and a route for leukocytes to
  enter into or exit from the lymphatic tissue of
  the node

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End CH 20 Lymph Node Anatomy