MEDS12003 Lecture Notes - Lecture 6: Lymphatic Vessel, Thoracic Duct, Extracellular Fluid
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Week 6 – lymph nodes
Lymphoid system
• Includes cells, tissues and organs for defending the body
against pathogens.
• Lymphocytes-functional unit
• Over 300 LN in neck
• Flat, bean shaped structures
• Very superficial 2-3cm below the skin
• Outer capsule, peripheral cortex, central medulla, indentation (hilum)
Cortex medulla of lymph node
CORTEX
• Composed densely packed lymphocytes
• Forming lymphoid follicles
• Low vascularity, hypoechoic
MEDULLA
• Composed of lymphatic sinuses, blood vessels, and connective tissue
• Hyperechoic, vascular
Structure of lymph node
Blood vessels of lymph nodes
• Main artery and vein enter and leave at hilum
• Arterioles branch through medulla, cortex to form capilliary lymphoid
follicles
• Parallel pathway of artery and vein
• Venules form lymphoid follicles –converge to form small veins
• Realtively avascular cortex is fed from central medullary vessels.
Lymph
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• Afferent lymph vessel (valves open TOWARD centre of node)
• Subcapsular sinus
• Trabecular sinuses
• Medullary sinuses
• Efferent lymph valves open AWAY from node.
Lymphatic circulation
Body circulation of lymph
• Rt lymphocytic duct in the Rt SCL vein
• Thoracic duct into Lt SCL vein
Crossing pressure gradients
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3 main functions
1. Drainage of excess interstitial fluid
2. Transportation of dietary lipids
3. Initiation of the immune response.
What is the function of lymph nodes
• They act as a filter to trap foreign substances so macrophages can
phagocytose
• Lymphocytes can mount immune response
• May be involved with metastases, lymphoma and infection
• Normal response to antigenic stimulus –increase size and vascularity.
Embryology of the neck
• Revise from Thyroid week
• Thyrogossal Duct Cyst
• Branchial Cleft cyst
Why is it important to scan nodes?
• Presence of nodes changes the management of
disease
• Characteristics of nodes helps to differentiate disease.
Normal lymph node
• Oblong or oval
• Hyperechoic central hilum
• Hypoechoic cortex
• Surrounding cortex is of mostly uniform thickness.
• Indiscrete (not sharp) border
• Size is not indicative….
Normal lymph nodes
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