During its active phase, the thymus is approximately 6 cm long and 2 - 3 cm wide.
The T-lymphocytes, which make up 75% of the blood lymphocytes, are formed in the thymus. The T-lymphocytes are the carriers of the cellular immune system, example, the body's defense against mutated cells (tumors) exogenous cells (transplants) and virus and mycosis infections.
The blood transports the T-lymphocytes to the secondary lymphatic organs (spleen, tonsils, lymph nodes), where they perform their tasks in the immune system. Most of the T-lymphocytes (90%) produced in the thymus are decomposed again in the cortex of the thymus, for reasons that are not known. .
The lymph nodes.
The lymph nodes are located along the lymph tracts. Several small lymphatic vessels enter the lymph nodes, but only one larger vessel leaves them again. They occur in groups at certain parts of the body, such as axillae or neck. The task of the lymph nodes is to control the lymph passing through them. They function as filters, restraining or destroying any bacteria arriving with the lymph.
There are regional lymph nodes, which receive lymph initially from an organ, and subsequent lymph nodes, which receive lymph from various regional lymph nodes. These are referred to as collective lymph nodes.
Each lymph node has a bean-like shape and is only a few millimeters in diameter. It consists of lymphatic tissue enclosed in strong connective tissue. Walls (trabeculae) penetrate into the node from the connective tissue and divide it into several chambers. Whereas numerous lymphatic vessels transport lymph into the node on the one side (vasa afferentia), the lymph only leaves the node through a few outgoing vessels (vasa efferentia).
Inside the lymphatic tissue, there are not only lymphocates, but also the large phagocytes (macrophagocytes). When lymph passes through the lymphatic vessels into the lymph nodes and lymphatic tissue, any foreign bodies such as bacteria or undissolved substances in the lymph are destroyed by the phagocytes.
