Lymph, also known as lymphatic fluid, is distributed throughout all organs of the body, mainly because lymph circulates in the lymphatic vessels, and the capillary lymphatic vessels are basically adjacent to the capillaries, except for the central nervous system, bone marrow, and organs without vascular structures, and are located almost throughout the body. Lymph, together with lymphatic tissue and lymphatic vessels, constitutes the lymphatic system, whose main role is to resist the invasion of viruses and bacteria and has an important role in the immune function of the body. If the lymph nodes are swollen and painful, it means that there is a virus or bacteria invasion, so you should go to the hospital in time to investigate the cause. In addition, if the normal structure of the lymph nodes is destroyed, resulting in lymphocyte hyperplasia, it should be taken seriously, as most of the diseases are caused by malignant lymphatic system diseases.