The lymphatic system consists of a widely branched network of lymph capillaries, which originate in the tissue fissures. These then form lymphatic vessels, which run parallel to the veins, transporting lymph in collective vessels. The lymph consists of some blood and other body fluids and is a cloudy, milky liquid. The main lymph duct is the thoracic duct. It flows into the superior vena cava.
There are numerous lymph nodes throughout the lymphatic system; these act as filters. They retain any infiltrated bacteria. Lymph nodes, which have a round or bean-shaped appearance, not only filter the lymph but they also form the lymphocytes. Lymph nodes are found in the neck, groin and hollow of the knee. Various organs, which have an anatomical and functional link with the system, are integrated into the lymphatic system.
They are divided into primary and secondary lymphatic organs, depending on their function. The primary organs include most importantly, the thymus and the bone marrow, because they are responsible for the formation, development and maturing process of the immune cells. The secondary organs refer to those organs into which the immune cells migrate. Together with the lymph nodes and lymphatic tissue of the mucous membranes such as the tonsils, intestine, and the spleen.
Thymus.
The thymus is a central lymphatic organ. It is a two-lobed organ in the upper part of the mediastinum behind the breastbone and extends down to the pericardium. The rear of the thymus touches the superior vena cava and the aorta arch .
The thymus is well developed in the newborn and growing adolescents. Here individual lobes can be detected, all located on one joint vessel section. Under the microscope, it is possible to detect a cortex and a marrow zone in the lobes, which branch again. In the cortex in particular there are numerous lymphocytes, but the marrow area has blood vessels and ultra-fine capillaries. The thymus is active up to the end of puberty, after which it recedes and degenerates.
