The lymphatic system is very similar and works with and directly alongside the cardiovascular system. The lymphatic system has a network of vessels like the circulatory system that pump a plasma-like fluid called lymph around its own lymphatic vessels and is found in most other tissues in the body except the central nervous system. Lymph is the name given to the fluid of plasma proteins that escape from the circulatory system at sites of the capillary network and diffuse into the cells around the capillaries. To allow the body to maintain a homeostatic fluid level and pressure, lymph must be returned to the circulatory system. The way this happens is that the network of lymphatic vessels captures fluid that has escaped and been absorbed by cells at the open ends of the lymphatic vessels, and transports it to a point where it can be reintroduced into the circulatory system. system. Two points in the shoulders, called the left and right subclavian canals, are where lymph is reintroduced into the cardiovascular system. In the lymphatic vessels, the lymph is examined and checked for disease-causing organisms, bacteria, and dead cells in sites along the vascular network called lymph. nodes. There are numerous lymph nodes within the vascular network, varying in size, with many vascular entry points, but only one vascular exit point per node. There are 4-5 nodes per vessel and once the lymph has been filtered through the first node, it moves to the second, third, etc., and can pass through up to 8 before reaching the ducts subclavians. This allows the lymph nodes to analyze the lymph and act accordingly. If the lymph node detects a pathogen, it releases antibodies called lymphocytes (white blood cells) to attack and destroy the foreign body. The node also...... middle of paper ...... bone, in T lymphocytes in the thymus. T cells are programmed to fight specific antigens entering the body and distinguish between body cells and tissues and foreign bodies in the body. This foreign material is isolated by the T lymphocytes and triggers the immune system to react against the foreign material, thereby destroying it. Since T cells are programmed to respond only to specific antigens, they would have no effect on other antigens and would therefore need programming to respond to these. T cells enter the bloodstream; some enter the lymphatic system and the others circulate in the cardiovascular system. The thymus develops from birth until adolescence when it reaches its peak. Beyond this, the size of the thymus and its effective capacity to produce T cells decreases, and by middle age it is approximately the same size as at birth..