The lymphatic system
The role of the lymphatic system
While nearly everyone knows about the circulatory system and its basic function, only a few people know there is another vascular system in our bodies: the lymphatic system. Arising from tissue between the blood vessels and cells, the "intercellular space" or "soft connective tissue", these lymphatic vessels run throughout the human body like a network of fine branches. The lymphatic system is responsible for most of the fluid uptake from the intercellular space and collects, transports and filters the substances dissolved in this tissue fluid, which is called lymph.
Das können z. B. Bluteiweisse, Stoffwechsel- oder Entzündungsprodukte, Giftstoffe, aber auch Bakterien und Viren sein. Like a "hazardous waste service", the lymphatic system transports up to 10 litres of fluid from the tissues per day and thus has an important role in the body's immune system and fluid regulation, as well as blood cleaning and filtering.
Structure of the lymphatic system
Starting from the finest lymphatic vessels in the tissues, the lymph is transported into ever larger vessels until it reaches the lymphnodes. The number of lymphnodes present in the human body is estimated at between 500 to 700; however, this differs from person to person. They play an enormously important role for the immune system: pathogens and even cancer cells are filtered out here and special immune cells are formed (lymphocytes).
After the lymphnodes, the lymphatic vessels come together to form lymph collecting ducts; these empty into the circulatory system in the large veins near the heart, thus transferring the lymphatic fluid into the venous system.
Lymph transport mechanisms
Transport in the lymphatic vessels occurs both passively and actively. During active transport, the lymph is moved by small muscular contractions of the vessel walls. In passive transport, tension in the skeletal muscles presses the lymphatic vessels together, propelling the lymph fluid forward. Owing to the fine valves in the lymphatic vessels, the lymph can only flow in one direction, namely towards the heart.
The intact lymphatic system
Blood circulating in the body tissues secretes waste products like proteins and fluids into the intercellular space when it passes through the fine capillaries. If the lymphatic system is intact, the excess fluid transfers into the lymphatic system via open-ended lymphatic capillaries.
The lymph initially collects in the lymph capillaries, which then combine to form larger lymphatic vessels with valves. There are lymphnodes at certain positions in the larger lymphatic pathways; these filter the lymph and contribute to immune defence.
The damaged lymphatic system
Lymphedema can develop when the flow of lymph is interrupted or disrupted, or when the secretion of fluid into the intercellular space exceeds the ability of the lymphatic system to take it up. Excess fluid collects in the tissues and can no longer be sufficiently drained. The tissue can swell as a consequence, leading to lymphedema in the affected area. Inflammatory reactions can develop if there is a longer-lasting congestion of the lymph in the tissue; these can lead to further damage to the lymphatic vessels and scarring of the surrounding tissue.