Lymphatic System and Immunity

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Lymphatic System and Immunity

• Chapter 16

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Functions of Lymphatic System

1. Draining interstitial fluid
2. Transporting dietary lipids
3. Protection

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Lymphatic Vessels

• Begin as closed ended lymph capillaries in tissue
  spaces between cells
• NOT A CIRCULATING FLUID
• Interstitial fluid drains into lymphatic
  capillaries, forming lymph.
• Lymph capillaries merge to form lymphatic
  vessels

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• Lymphatic vessels carry lymph into and out of
  lymph nodes
• and finally back to the vascular system.

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Lymphatic capillaries

• Made of a single layer of squamous epithelial
  cells
• Slightly larger than blood capillaries
• Cells overlap and act as one-way valves
• Opened by pressure of interstitial fluid
• Anchoring filaments attach cells to surrounding
  tissue

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Lymphatic vessels

• Resemble veins (same 3 layers)
• Found throughout body except
• Avascular tissues
• Central nervous system
• Splenic pulp
• Bone marrow

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Lymphatic vessels join to form lymphatic
trunks. Lymphatic trunks join to form Thoracic
duct (3/4 of body) Right lymphatic duct (drains
right arm, and right side of head, neck and
upper torso) These empty into subclavian veins at
junction with internal jugular vein.
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Formation of lymph Fluid leaves capillaries by
diffusion and filtration Escaped proteins If
lymph flow blocked tissue swelling or
edema Specialized lymphatic capillaries in vili
of small intestine transport lipids - they are
called lacteals, and the fluid is called chyle.
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Lymphatic Organs

• Red bone marrow Primary organs
• Thymus gland
• Lymph nodes
• Lymph nodules Secondary organs
• Spleen

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Lymph Nodes

• Lymph is filtered through lymph nodes
• Found in clusters
• Waste water treatment plants
• Vary in size
• Principal groupings in cervical, axillary and
  inguinal regions.
• Provide biological filtration
• Site of cancer growth and metastasis

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• Vessels enter node on convex side
• Lymph passes through irregular channels called
  sinuses
• Leaves node through one or two efferent vessels
  at the hilum or hilus
• Capsule, cortex and medulla
• Cortex contains lymph nodules
• Follicular dendritic cells
• Germinal centers B cells proliferate

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Lymph nodules are also found singly or in groups
throughout the mucous membranes of the
respiratory, urinary, reproductive and digestive
tracts. MALT mucosa associated lymphoid
tissue Peyers patches in ileum Tonsils Some in
appendix
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Tonsils lymphoid tissue under the mucous
membranes of the throat palatine
tonsils pharyngeal tonsil adenoid lingual
tonsils First line of defense Tonsillectomy
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Thymus gland

• in mediastinum above the heart
• largest at age 10-12 then begins to atrophy
• Pre - T cells come from bone marrow and develop
  into T cells
• T cells then go to other lymphatic tissues
• Thymus produces hormone thymosin - aids
  maturation of T cells elsewhere in body

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Spleen

• Largest lymphoid organ
• In upper left quadrant of abdomen
• Has a hilum and a capsule
• Sinuses contain blood instead of lymph

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White pulp little islands, mostly B cells Red
pulp Venous sinuses Splenic cords RBCs,
macrophages, lymphocytes, plasma cells and
granulocytes
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