The Lymphatic System is part of the circulatory system. What it actually does is drain the protein-containing proteins from the blood capillaries. The escaped fluid becomes the lymph once absorbed by the lymph capillaries. Lymphatic capillaries are located in the interstitial spaces between the cells where fluids accumulate. These capillaries are slightly larger and more permeable than the blood capillaries. The lymph capillaries converge into larger lymph vessels, the lymphatics, which resemble veins but have thinner walls and more valves. The lymphatics just under the skin usually run parallel to veins, while those in the viscera generally follow arteries. .
Besides returning fluids back to the bloodstream, the lymphatic system is also an important part in the absorption of fat from the intestines. On the other hand, blood seems to be much better at absorbing sugars and amino acids from the intestines. .
Located along the major lymph vessels is a series of nodes known as lymph nodes, or lymph glands. These are made of a matrix of connective tissue harboring phagocytotic cells that filter out and clean the lymph by ingesting bacteria, cell fragments, and entire cells. The lymph glands then return these wastes to the blood where they are carried to the lungs, kidneys, and sweat glands that eliminate them from the body. Also, these wastes are detoxified when they pass through the liver. When the body is fighting infection, the lymph nodes become swollen and more sensitive.
In addition to filtering and processing lymph, the lymph nodes, along with other lymphoid tissues such as the spleen, thymus, and tonsils, are the sites where certain white blood cells, known as lymphocytes, are formed.
The lymph is moved by a process similar to that which moves blood through the veins. A series of one-way valves work in conjunction with the pressure applied by the contraction of nearby skeletal muscles that constantly squeeze the lymph forward in a one-way direction.