Lymphatic System
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Lymphatic System
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Functions
Return fluid to general circulation
Production of WBCs
Immunity
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Lymphatic Vessels
• Open circulatory system
• Originate blindly in tissue interstices
throughout the body except CNS and
those without blood supply
• Thin walled - endothelium only
• Permeable
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Lymphatic Vessels
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Lymphatic Vessels
• Parallel venous flow
• Asymmetrical distribution
• Two major junctions with cardiovascular
system
– Thoracic duct into left subclavian vein
– Right lymphatic duct into right subclavian
vein
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Ducts
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Lymphatic
Vessels
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Lymphatic Physiology
• Movement into lymphatic capillaries
function of osmotic pressure
• Valves and muscular activity assist
return flow
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Lymphatic Organs
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Lymph nodes
Spleen
Tonsils
Thymus
Diffuse tissue
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Lymph Nodes
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Distributed along vascular pathway
Filter lymph
Encapsulated by dense CT
stroma/framework of reticular fibers,
trabeculae
• Parenchyma of cortex and medulla
• Lymphocytes/t cells
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Lymph
Nodes
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Lymph Nodes
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Macrophages
B lymphocytes/b cells
Multiple afferent lymphatics
Usually a single efferent exiting at
hilus/hilum
• Size variable 1-25 mm, change with
infection
• Secondary tumor sites via metastasis
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Spleen
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Functions
Fetal blood development
Store and release blood during stress
Recycle old blood cells
B cell maturation into plasma cells
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Spleen Structure
• 12 cm oval body in left hypochondriac
region
• Splenic artery and vein enter at hilus
• Covered with peritoneum
• Structure similar to lymph node
• Parenchyma of two types
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Spleen Structure
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Red pulp
Blood filled venous sinuses
Splenic cords/Billroth’s cords
White pulp
Lymphocyte production
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Tonsils
• Aggregated lymph nodes
• Concentrated in Waldeyer’s tonsilar ring
– Lingual
– Palatine
– Pharyngeal/adenoid
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Thymus
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In superior mediastinum
Two lobes
Surrounded by CT capsule
Cortex = reticular fibers + lymphocytes
Medulla - epithelial cells produce thymosin
stimulating maturation of T cells, form
Hassall’s corpuscles
• Maximum size 10-12 yrs old ~ 40 grams,
degenerates with age
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Diffuse Lymphatic Tissue
• Not encapsulated
• Widely distributed throughout body
• Found in lamina propria of digestive
tract, respiratory, urinary and
reproductive systems
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Pathology
• Lymphangitis
• Lymphadenopathy
• Edema
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