As part of the immune system, the lymphatic system is distributed throughout the body. It is not a single organ, but a complex network of lymphoid organs and lymphatic vasculature.
What is the lymphatic system?
The term lymphatic system comes from Latin. Here, the word lympha means “clear water.” In this system, the lymphatic fluid is formed, which has a great importance for the fluid transport in the body. Thereby the lymphatic system represents a part of the immune system. Furthermore, it is closely connected with the blood circulation. It includes the totality of all lymphatic channels and so-called lymphatic organs. These organs are responsible either as primary lymphatic organs for the formation of the defense cells or as secondary lymphatic organs for the multiplication of these cells by cell division. The lymphatic vascular system, in turn, consists of lymphatic capillaries in which the so-called lymph nodes are integrated as filtering stations. It plays an important role in the transport and filtering of body fluids. With the help of studies of the response of the lymphatic system, many diseases, ranging from infections to autoimmune disorders and cancer, can be diagnosed.
Anatomy and structure
As mentioned earlier, the lymphatic system is distributed throughout the body. It includes the lymphoid organs and the lymphatic vascular system. There are primary and secondary lymphoid organs. Primary lymphatic organs include, for example, the thymus and bone marrow. These organs serve the formation and transformation of defense cells (lymphocytes). The secondary lymphoid organs are represented by the tonsils, spleen, lymph nodes, lymphoid follicles, Peyer’s plaques, and vermiform appendix. They are responsible for the specific immune response through the encounter of lymphocytes and antigens. They also provide for the proliferation of lymphocytes as a result of cell division. The spleen and bone marrow are also responsible for the formation, storage and breakdown of blood cells. The lymphatic vascular system is a system of lymphatic capillaries that filter and transport fluid from the organs and intercellular spaces. The so-called lymph nodes serve as filtering stations. The fluids from the blood circulation and the intercellular space are in close communication through the lymphatic vascular system. The union of the lymphatic fluid with the blood takes place in the superior vena cava. All other organs in the body each have their own lymphatic system, which is connected to the overall system.
Function and tasks
The functions of the lymphatic system include both defense against pathogens and fluid transport in the body. In the primary lymphoid organs, the thymus and bone marrow, T and B lymphocytes are differentiated from existing precursor cells. B lymphocytes are part of the white blood cells and are the only cells capable of forming antibodies. Together with T lymphocytes, they are the most important component of the immune system. The T lymphocytes are formed in the thymus. As T-killer cells they destroy diseased cells, as T-helper cells they attract additional immune cells, and as regulatory T-cells they prevent an excessive immune reaction to the body’s own cells. The secondary lymphoid organs are responsible for the immunological response to foreign invaders through the proliferation of immune cells and the encounter of antigens on immunocompetent lymphocytes. Immune cells are distributed through the bloodstream and the lymphatic vascular system. Within the lymphatic vasculature, the lymph nodes control the filtering of lymph and contribute to the immune response in infections through the proliferation of lymphocytes. This is evident by the swelling of lymph nodes. The lymphatic system is also responsible for the transport of lymphatic fluid. However, there is no lymphatic circulation. Via the lymphatic system, there is only a connection of intracellular fluid with the blood circulation. In this process, parts of the blood exit via the capillaries as intercellular tissue water. In these capillaries, the transport of fluid occurs either passively through the movement of the limbs or actively through disordered contractions of individual lymphangions. These are sections of lymphatic vessels whose smooth muscles can assume pumping functions by contraction.The lymphatic system is also responsible for transporting fats from the intestines into the bloodstream.
Diseases
Because of its central function in immune defense, the lymphatic system often provides clues to infectious disease in the body. For example, increased production of immune cells is often indicated by swelling of lymph nodes. In most cases, the swelling of the lymph nodes occurs at the source of the infection, so that the physician can obtain valuable clues for his diagnosis based on their localization. However, this is not always possible. In severe infections, there may be a generalized reaction of the lymphatic system. Sometimes there is chronic swelling of the lymph nodes, which can have various causes. Since the immune system fights not only bacteria, viruses or fungi, but also pathological endogenous cells or cancer cells, it often requires intensive diagnostic examinations by the physician. Therefore, in addition to infections, tumors or autoimmune diseases also lead to lymph node swelling. The lymphatic system itself is also susceptible to diseases. For example, a lymphoma (cancer of the lymph glands) can develop as a result of an undifferentiated proliferation of lymphocytes. Typical symptoms of this disease are chronic but painless swelling of the lymph glands, fatigue, fever and weight loss. However, with a combination of chemotherapy and radiation therapy, lymphoma has a good prognosis. Another disease popularly known as sepsis is lymphangitis, an inflammation of the lymphatic system. Furthermore, the drainage of lymph may be disturbed. Lymphedema develops, with swelling of the affected area of the body. It should also be mentioned in this context that the individual organs of the lymphatic system can also develop individual diseases.
Typical and common diseases
- Hodgkin’s disease
- Blood poisoning
- Lymphedema
