Lymphatic vessels form a tubular structure and serve to transport aqueous solutions. In the body, they run alongside veins and arteries.
What are lymphatic vessels?
Lymphatic vessels resemble the shape of blood vessels. However, they are not responsible for transporting blood, but for transporting lymph. Lymph is a light yellow fluid. It has proteins, fats and water. It also contains important immune cells, which are essential for the body’s defense. Lymph is found throughout the body tissues, which is why lymphatic vessels are found in all tissue occurrences. Exceptions are bones, cartilage and the teeth. In connection with the lymphatic vessels, the lymph nodes also play an important role. The lymph nodes are an important part of the defense system. They act as a filtering station and have the task of cleaning lymph. Together with the lymphatic vessels, the lymph nodes form the lymphatic system of the human body. The vessels begin as a small branch system and join together to form large pathways. They lie parallel to venous vessels and run throughout the body.
Anatomy and structure
Lymphatic vessels are divided into four types. Each is associated with different characteristics and tasks. However, the vessel types also share some common features. For example, all lymphatic vessels consist of three wall layers. The innermost layer is the intima. This is followed by the media and the adventitia.
- The lymphatic capillaries form the finest form of the four types of vessels. With them, the lymphatic system manages to reach into the deepest tissue layers. In the form of a branch system, lymphatic capillaries are able to absorb even small occurrences of tissue fluid. As the smallest unit of the lymphatic vascular system, capillaries have a width of 50 µm.
- The precollectors form the next stage. They collect the tissue fluid and pass it to the third type of vessel, called collectors.
- The collectors contract at regular intervals to push the lymph to the next collectors.
- Finally, the lymphatic collectors form the largest vascular form of the lymphatic system. They collect lymph from the collectors and empty into the venous circulation. Unlike blood vessels, lymphatic vessels do not form a closed system.
Function and tasks
Primarily, lymphatic vessels are responsible for the return of the remaining lymph. This is tissue fluid that has not been fully reabsorbed by the blood vascular system. Protein molecules are also involved. They are transported back into the venous bloodstream together with the tissue fluid. Furthermore, the immunobiological effect is one of the most important tasks of the lymphatic vessels. It protects the body against infections and foreign antigens. In addition, defense substances are produced that support the immune system. Another function of the lymphatic vessels is to transport fats. As part of the digestion of fats, they are absorbed with the diet. In the small intestine, they are packed into so-called chylomicrons. They then enter the blood via the lymphatic vessels. Furthermore, thanks to the lymphatic vessels, the body manages to dispose of metabolic products, foreign bodies and pathogens. This also applies to the lymph nodes. They perform a cleansing function and support the immune system in its defense. Furthermore, lymphatic vessels have the task of reliably transporting proteins back into the body. Specifically, they should succeed in preventing large accumulations of protein molecules in the interstitium. Interstitium is the term used to describe intermediate tissue such as connective, supporting and muscle tissue. If the pressure were to increase due to an accumulation of protein molecules, disturbances in the blood flow could occur. Last, lymphatic vessels perform the task of transporting chylomicrons from the gastrointestinal tract. Chylomicrons are small particles that contain cholesterol.
Diseases and ailments
Lymphangitis and lymphedema are the most common diseases of the lymphatic vessels. Lymphangitis is also known colloquially as blood poisoning. It is an inflammation of the lymphatic vessels, mainly on the skin and in the subcutaneous fatty tissue. Lymphangitis can be attributed to bacterial infection. The primary triggers are streptococci and staphylococci.In rare cases, lymphangitis is triggered by the consumption of chemotherapeutic agents or other cytostatic drugs. The symptom is a red spot on the skin above the inflamed lymphatic channels. In the advanced stage, fever and malaise are the consequence. Usually, lymphangitis can be treated well with antibiotics. In contrast, lymphedema is a palpable accumulation of fluid in the interstitial space. The edema can occur in the extremities, face, and genitals. In this case, a disturbance of the lymphatic system leads to the fact that the tissue water can no longer be removed. The accumulation of fluid is accompanied by an inflammatory clinical picture. Causes include previous infectious diseases, cardiac insufficiency, kidney disease, liver problems and thyroid disease. In the course of the disease, lymphedema can be divided into a primary and a secondary variant. Both variants share the common feature that the lymphatic loads are not managed. A distinction is made in the course analysis. Primary edema occurs in the legs and can be attributed to a hormonal change. In contrast, secondary lymphedema is the result of tissue destruction. Triggers include burns, chemical burns, and skin sloughing. Massage techniques and compression bandaging can achieve mitigation. In addition, exercise therapy can provide relief. In particularly severe cases, supermicrosurgery is performed. The aim is to restore the functionality of the affected lymphatic vessels. Small incisions succeed in reducing lymphatic water retention in the long term.
