Most lymph nodes are located in the head, neck, armpits and groin area, explains Mayo Clinic. There are hundreds of these nodes in the body located in other regions such as the joints, elbows and knees and around the lungs and bowels, states the American Cancer Society.
Lymph nodes are located throughout the body and connected by vessels to make up the lymphatic system, an important aspect of the immune system, says the American Cancer Society. Lymph flows through the lymphatic system and is a fluid rich in oxygen and nutrients. It is also the network through which waste products are removed from the body. Part of the lymph fluid are white blood cells that fight infections. The nodes act as filters that remove waste such as infectious cells that are carried in the fluid.
Sometimes these nodes swell, becoming tender and painful, according to Mayo Clinic. Usually, this is a sign of some sort of infection. Often swollen nodes are self-resolving, returning back to their normal size once the white blood cells successfully fight the infection. In some cases, however, lymph nodes remain swollen for several weeks, take on a hard or rubbery texture and are accompanied by illnesses. These are possible signs of a more serious problem, such as lymphoma or leukemia, lupus, tuberculosis or the HIV virus.