The lymphatic system contains a fluid called lymph. The system has multiple functions:
- Draining excess interstitial fluid from the interstitium into the blood
- Carrying proteins and other large proteins, which are too large to be absorbed into the capillaries.
- Absorbing fats from the GI tract
- Transport of lymphocytes, antibodies and pathogens
All tissues have lymphatic vessels, which eventually drain into the thoracic duct and later the left internal jugular vein.
Because one of the major functions of lymph is to drain proteins from interstitial tissue, the lymph has a high concentration of protein.
Movement of lymph:
Lymphatic vessels have one-way valves which prevents lymph from flowing back into the interstitium. Lymph is pumped through the vessels by both internal and external mechanisms.
The lymphatic vessels themselves are muscular. They contract in synchronized waves which push the lymph forward.
Skeletal muscle contraction is the most important external mechanism with which the lymph is pumped. When surrounding skeletal muscles contract, like when walking, lymph is pumped through the lymphatic vessels.
25. Circulation through the capillaries
27. Circulation in the vein. Effect of gravity on circulation