· Lymph composition
· Anatomy
· Physiology
· Water
· Electrolytes
· Protein (almost from liver due to permeable sinusoids - total 20g/L, hepatic 50g/L)
· Fat (almost all from gut via cisterna chyli)
· Carbohydrate
· Immune cells (antigen-presenting cells including dendritic cells, macrophages)
· All coagulation factors (but low level of fibrinogen)
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Lymphatics |
· Located in all tissues except bone, cartilage, brain · Three layers: intima, media, adventitia · Anti-reflux valves · Superficial lymphatics travel with veins · Deep lymphatics travel with arteries |
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Ducts |
· Right lymphatic duct: drains RUL, R H&N, R hemithorax · Thoracic duct: drains everything else (N.B. Virchow’s node in supraclav fossa) |
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Lymph nodes |
· Large groups in axilla, inguinal, cervical regions (for UL, LL, H&N respectively), abdomen · Cisterna chyli: dilated sac at the lower end of the thoracic duct (for GIT) |
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Circulation |
· Extrinsic pump: compression by skeletal muscle or arterial pulsation · Intrinsic pump: smooth muscle · Valves ensure unidirectional flow · Production: 8-12L/day (↑if exercise, capillary leak e.g. sepsis, anaphylaxis) · Reabsorption: 4-8L/day via LNs; 4L/day via ducts (↓ if lymphoedema, radiation, obstruction) |
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Role in health |
· Return extravasated fluid and protein to circulation, minimise oedema · Transport ingested fat to circulation (bypass liver -> prevent fatty liver) · Transport antigen-presenting cells to lymph nodes · Formation of concentrated urine: removal of protein-rich ISF from medulla, allows water to enter vasa recta, preserves osmotic gradient |
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Role in disease |
· Lymphoedema o Destruction e.g. surgery, radiation o Obstruction e.g. tumour |