The lymphatic system functions as the body's chief protection against infection. It is the cleaner of the body consisting of four organs: the lymph nodes, tonsils, thymus and spleen. Although dispersed throughout the entire body, the heaviest concentration of lymph nodes are in the cervical spine, the armpit or axillary area and the groin or inguinal region. There are also a great number of lymph nodes in the abdominal and pelvic areas, with most of these embedded in fatty tissue.
Lymph nodes are located along the lymphatic network of vessels throughout the body. The primary purpose of the lymph nodes is to clean the lymphatic fluid as it passes through the body. This fluid continually flows out of your blood capillaries and into tissue. The fluid contains fats, foreign cells, chemicals and toxins. The lymph nodes' job is to alert the immune system to a foreign substance (antigen) in order that the proper protector cells (white blood cells) can be produced. If the antigen’s challenge is too great for the lymph node, it may become swollen and painful. One of the reasons doctors press on your stomach, armpit and groin areas during their exams is because they are looking for signs of swelling in the lymph nodes. As the lymph flows from one lymph node to another, it becomes thoroughly cleansed of most of its impurities. It then filters back into the bloodstream.
Lymph nodes are elongated or kidney-shaped, and are usually less than 3 cm long. Lymphocytes are specialized white blood cells in the lymph nodes that help fight infection. The two principal types are T-cells, so named because they develop in the thymus and B-cells, which over time develop into plasma cells as they produce antibodies. When lymphocytes become enlarged as they encounter antigens (germs or bacteria), they are called immunoblasts.
The tonsils are first line of defense in the lymphatic immune system. Because of their location at the entrance to the pharynx (back of the throat), they guard against toxins that would seek to enter the body through the mouth and nasal cavities. Although at one time a tonsillectomy was a common procedure in children when tonsils became chronically swollen, it is done less often today as development of more powerful antibiotics have occurred. The thymus, an organ in both the lymphatic and endocrine systems, is located between the sternum and the aortic arch. In early childhood, the thymus is at its most active, secreting hormones and providing a storage space for developing lymphocytes. As we age, the thymus is gradually replaced by fatty tissue. The spleen, the largest of the lymphatic organs, is located just under the top of the diaphragm and next to the stomach. In the fetus, the spleen produces blood cells and it may resume this function if an adult becomes extremely anemic. The spleen's primary function, however, is monitoring of the blood for foreign substances. Old red blood cells as well as blood-born bacteria are filtered through to the spleen and are consumed and eliminated. In the case of severe injury to the spleen, it can be removed, but through its removal a person may become more susceptible to infection.
Disorders of the lymphatic system can wreck havoc with the body's immune system. Lymphadenopathy is the most common and generally manifests as a swollen lymph node. Many times a simple massage to help the lymph fluid unclog and flow or a simple course of antibiotics is required. Many times an infection near the lymph node, such as a sore throat, can cause the lymph node to swell. Lymphadenitis is an infection of the lymph node itself, and requires intervention from a medical professional. Usually the infection is not serious, but it can be painful as the lymph node swells, becomes tender and is frequently red and warm to the touch. Lymphoma is cancer of the lymph nodes, most commonly in the axillary region (armpit) which is in close proximity to the breasts.
Like, the circulatory system, the lymphatic system is a network of vessels. Unlike the circulatory system, the lymphatic system has no "pump" located within the lymph vessels and must reply on bodily movement as well as nearby pulses from other vessels and organs in the body to facilitate the flow of the lymph fluid. In other words, if you do not move, the lymph does not move well. Very sedentary individuals are frequently sicker than their thinner counterparts for this very reason. Active people move more, their lymphatic fluid moves more and the lymph nodes are able to cleanse their bodies of infection at a much faster rate.