Capillaries are not in direct contact with cells, so substances filter out of them into the interstitial plasma (fluid in which cells are immersed) and cells take and release substances from and into this interstitial plasma.
Liquid and nutrients are continuously going out of the blood capillaries and waste products are released into the interstitial plasma. What are we missing here? Intertitial fluid must be collected, with all that waste, and then returned to the bloodstream. This is one of the 3 roles of the lymphatic system. What are the other two?
You might need to know that it is formed by lymphatic vessels (lymphatic capillaries which join together to form lymph-collecting vessels), lymph nodes and lymph.
Lymphatic capillaries are blind-ended (closed at the end) and interstitial fluid enters by filtration (through the epithelium). This fluid travels through larger vessels, is filtered and processed by the lymph nodes, and then goes to the bloodstream via left and right subclavian veins. Can you see the internal medium circuit? blood plasma-interstitial plasma-lymph-blood plasma.
Lymph nodes are located along some lymphatic vessels (clearly noticeable in your neck, armpits and groins). They produce lymphocytes (one type of leukocyte), release them into the vessels and filter waste out from the vessels.
Lymph:
I'm sure you realized I already gave you the second function, but what about the third one? It has to do with the digestion process.
One more thing, all of us have an especially large lymph node called spleen. When did we mention it before? (hint: something is destroyed there) and, what other functions does it carry out?
Probably, you have found a few functions, all of them quite important, however, life is possible after its removal.
One final note: this system does not have a pump, so, how does the lymph circulate? I'm sure you already know this.
(From naturalscience3doctormaranon.blog)
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