The Lymphatic System

The lymphatic system is very similar, and works with and directly at the side of the cardiovascular system. The lymphatic system has a network of vessels like the circulatory system which pump a plasma-like fluid called lymph around it’s own lymph vessels, and are found in most other tissues of the body, except the central nervous system.

Lymph is the name given to the fluid of plasma proteins that escape the circulatory system at the sites of the capillary network and diffuse into the cells around the capillaries. To enable the body to maintain a homeostatic fluid level and pressure, the lymph must be returned to the circulatory system. The way this happens is for the the network of lymph vessels to pick up the fluid which has escaped, and been absorbed by the cells at open ends of the lymph vessels, and carry it to a point where it can be put back into the circulatory system. Two points in the shoulders called the left and right subclavian ducts are where the lymph is reintroduced to the cardiovascular system.

Within the lymph vessels, the lymph is screened and checked for pathogenic organisms, bacteria and dead cells at sites along the vessel network called lymph nodes. There are many lymph nodes within the vessel network of varying sizes that have numerous vessel entry points, but only one exit vessel point per node. There are 4-5 nodes per vessel and after the lymph has been screened by the first node, it travels onto the second, third etc., and can pass through as many as 8 before it reaches the subclavian ducts. This allows the nodes to analyse the lymph and act accordingly. If the node detects a pathogen, it releases antibodies called lymphocytes (white blood cells) to attack the foreign body and destroy it. The node also ...

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... bones, into T-lymphocytes in the thymus. T-lymphocytes are programmed to fight specific antigens entering the body and distinguish between body cells and tissues, and foreign matter within the body. This foreign matter is isolated by the T-lymphocytes and triggers the immune system to react to the alien matter thus destroying it. Because the T-lymphocytes are programmed to only react to specific antigens, they would have no effect on other antigens and therefore would need programming to react to these. The T-lymphocytes enter the bloodstream; some enter the lymphatic system and the others circulate around the cardiovascular system. The Thymus gland grows from birth until adolescence where it reaches its peak. Beyond this, the thymus reduces in size and effective ability to produce the T-lymphocytes and by middle age, is roughly the same size as it was at birth.