The lymphatic system comprises a network of lymphatic vessels, lymph nodes, and several other organs, distributed throughout the body as a network. These structures collect fluid called lymph from the body and return it to the blood stream, thus maintaining the body’s fluid balance. Besides being part of the circulatory system, this system also maintains the immune system by repelling foreign substances.
The basic function of lymph vessels is to carry lymph (a clear fluid drained by the lymphatic system, containing large proteins as well as plasma proteins of blood) from peripheral tissues to the veins of the cardiovascular system. The lymph nodes, on the other hand, monitor the consumption of lymph, engulf pathogens, and carry out immune responses in the human body. Besides lymph vessels and lymph nodes, the spleen and thymus are also associated with this system. The lymphatic system returns blood to the heart by means of two main vessels, called thoracic duct and right lymphatic duct.
Image courtesy: thejoyofreflexology.com
The immune system provides long term immunity to the body against certain diseases, and protects it against viral and bacterial invasions. The immune system does not have specific organs to carry out its functions. It is composed of a series of cells and agents that are located in the lymphatic system, mainly through the lymph nodes, tonsils and spleen. During the fetal stage of human development, the stem cells of bone marrow also develop into the organs of the immune system.
Image courtesy: healthy-proteins.blogspot.com