Lymphatic System
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Lymphatic System
Lymphatic System
- Lymph is a liquid formed by
- interstitial fluid leaked from capillaries
- Any fluid not reabsorbed by capillaries will be drained into lymphatic vessels
- Transport of proteins and large particles (e.g. waste products) that are too large to directly enter the capillaries
- Fats from intestines
- Absorbed lipids from food packaged into large droplets, called chylomicrons
- Droplets are too large to directly cross over into blood; transported through the lymphatic system to indirectly enter circulation
- interstitial fluid leaked from capillaries
- Structure
- Lymphatic vessels
- Function: collection and transport of lymph
- Contain one-way valves to ensure unidirectional movement
- Overlapping endothelial cells form walls of lymphatic vessels to prevent leakage
- Smooth muscle around vessels contracts to push fluid along
- Adjacent skeletal muscle can also pushes fluid forward
- Lymph flow is greater in an active person than an individual at rest
- Lacteals are lymphatic vessels in the small intestine
- Function: absorb fat as chylomicrons
- Order of flow
- Lymph capillaries → lymph vessels → lymph duct → veins
- Dumped into veins via lymphatic ducts, which include the thoracic duct and right lymphatic duct
- Lymph capillaries → lymph vessels → lymph duct → veins
- Function: collection and transport of lymph
- Lymph nodes
- Small clusters of cells along lymphatic vessels
- Function: filters lymph as it flows through
- Monitoring by resident lymphocytes
- Scan for foreign antigens in lymph, launching immune responses if necessary
- Macrophages also destroy pathogens via phagocytosis
- Monitoring by resident lymphocytes
- Spleen
- Largest organ in the lymphatic system
- Function: filters blood
- WBCs in spleen recognize and bind foreign antigens in blood
- Can launch immune responses if necessary
- Splenic macrophages destroys old and damaged RBCs
- Stores extra blood components (e.g. platelets, RBCs)
- WBCs in spleen recognize and bind foreign antigens in blood
- Lymphatic vessels