Lymph glands are part of the lymphatic system and are classified as secondary lymphoid organs. As such, they are part of the immune system and perform an important function in defending against infection from bacterial and viral germs. They filter or cleanse the lymph released from the bloodstream and return it, and the provision and activation of B and T lymphocytes and macrophages play a major role in this process.
What are the lymph glands?
Lymph glands are also referred to synonymously as lymph nodes because they are not glands in the original sense, but as part of the lymphatic system they perform an important function of the body’s immune system by providing and controlling the activation and proliferation of specific white blood cells such as B and T lymphocytes. Lymph glands virtually filter the lymph (tissue fluid) released from the bloodstream into the tissues, examine it for infectious viruses or bacteria and for degenerate own body cells. The lymph then returns to the bloodstream. The lymph glands normally reach a size of 5 to 10 mm, but can reach almost twice that size in the neck and groin. The frequency distribution of lymph glands, each of which “attends” to and monitors a particular region of the body, is uneven. Important regions for accumulations of lymph glands include the head, neck, and axilla, as well as the abdomen and chest. Many lymph glands can be palpated externally as small, inconspicuous thickenings of tissue. If the lymph glands have detected infectious germs in the lymph, they may become active and swell significantly.
Anatomy and structure
Lymph glands usually have an elongated oval kidney-like shape and are surrounded by a firm connective tissue capsule from which septa (trabeculae) extend into the interior of the lymph gland. The interior of the lymph glands consists of very fine lymphreticular tissue composed of reticulum cells and of free lymphocytes. The tissue is divided into three layers, the cortex, the middle paracortical zone, and the inner medulla. The lymph glands are traversed by cavities, the lymph sinuses, in which the lymph virtually moves from one station to the next. The so-called primary lymph from the surrounding tissues is collected in lymphatic vessels, which enter the lymph glands as vas afferentia. After processing the lymph inside the lymph glands, the lymph leaves the lymph gland via the centrally located vas efferens through the hilus and is either directed to a collecting lymph gland or back into the bloodstream. Various lymphocytes such as B and T lymphocytes are found in the individual layers of the lymph gland, while macrophages are found in the medulla. The lymphocytes can be activated very quickly and, depending on the nature of a threat, can differentiate and intervene as part of the immune response.
Function and tasks
The main task and function of the lymph glands is to absorb tissue fluid and check for any pathogenic viruses, bacteria or degenerate own body cells or other harmful substances. The rather smaller regional lymph nodes take up the so-called primary lymph of the surrounding tissue and, after a certain processing, pass it on to so-called larger collecting lymph glands, which process the lymph of several to many regional lymph glands and return it to the bloodstream. In the case of recognized danger of infection by harmful viruses or bacteria, the lymphocytes in the lymph glands react with the means of the immune system. By phagocytosis, harmful particles are first trapped (eaten) in the phagocytes and, if possible, later broken down into harmless pieces by enzymatic means and excreted. Another method of combat is direct attack via antigens. In addition, T cells, for example, are able to summon help from other parts of the body if necessary. Cytotoxic T cells, which can identify infected endogenous cells and degenerated cancer cells in particular, have the ability to produce certain cytokines (messenger substances) that trigger apoptosis, pre-programmed cell death, in the endogenous cells recognized as infected or degenerated. Immune responses can also consist of stimulating the body to run a fever, because many viruses are very sensitive to temperature and biochemical processes in the body are significantly accelerated at elevated temperatures, so that two effects are achieved simultaneously.
Diseases
As a component of the immune system, the lymph glands or their lymphocytes are often involved with immune responses, which is usually accompanied by palpable and sometimes painful swelling of the affected lymph glands. When all lymph glands have swelling, it indicates a systemic problem affecting the entire body metabolism. The systemic reaction of the lymph glands can be caused, for example, by a viral disease such as rubella or Pfeiffer’s glandular fever, or by a bacterial disease. Similar symptoms also appear some time after an AIDS infection. Local infections and inflammations usually affect only certain lymph glands that are “responsible” for the infected tissue. Respiratory infections offer an example, in which mainly cervical lymph glands show symptoms and may swell painfully. It is very rare that the lymph glands themselves become diseased and therefore develop corresponding symptoms, however, cancers originating from the lymphatic system are more common. These are so-called lymphomas, which can be less to very aggressive. A distinction is made between Hodgkin’s lymphoma and non-Hodgkin’s lymphoma. Both forms initially manifest themselves in systemic painless swellings of the lymph glands. Another variant of a less malignant lymphoma is chronic lymphocytic leukemia. Despite the often aggressive development of lymphoma, these cancers are now treatable with good prognosis with chemotherapy and radiation therapy. In other cancers that tend to metastasize, the degenerate cancer cells may end up in the lymphatic system and metastasize there.
Typical and common lymph node diseases
- Pfeiffer’s glandular fever
- Lymph node swelling
- Burkitt’s lymphoma
- Lymphadenitis
- Lymphangitis
