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Human Body
THE LYMPHATIC SYSTEM
The lymphatic system communicates with the blood circulatory system and is closely associated with it. It has several functions which complement the function of the blood circulatory system.
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Though technically the blood circulatory system is a closed system, there is a continuous leakage of fluid and proteins out of the capillaries into the tissues. To prevent the blood from thickening, the fluid must be returned to the system. This service is provided for by the 'lymphatic system'. Almost all tissues have lymphatic channels, which drain excess fluid into this system. It can be regarded as a part of the circulatory system. Besides returning bodyfluid to the blood, it transports substances such as fats, hormones and enzymes from their manufacturing sites to the blood-stream.
Lymph-the fluid which has passed into the lymphatic vessels is a watery plasma-like fluid. Wherever there are blood-vessels, there are also lymph-vessels. Lymphatic system resembles blood-system. Lymph capillaries unite to form large vessels which unite, in turn, to form larger vessels. Finally, they converge into two main ducts which empty into the various portions of the blood-system.
Lymph-capillaries are very thin-walled tubes which are even more permeable than blood-capillaries, but it is a one way permeability. Once, fluid, protein and other particles have entered, they stay inside and cannot leak into the tissue.
Lymphatic system is also the head quarters for the important line of defence against diseases. It provides the body with lymphocytes and other anti-body-producing cells for defending it against disease-germs and other foreign invaders.
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