Lymphatic System

The most common causes of visible lymphoid activity are infection and neoplasms. Infection is the most common cause of lumps in children’s necks. An understanding of which areas are drained by the nodes is useful in further assessment of present or past infections. Detection of enlarged nodes and an enlarged spleen can be critical to the early diagnosis and treatment of serious disorders.

The lymphoid system is a system of lymph fluid, collecting ducts, and tissues. Although the specific functions of lymphoid tissue are still not fully understood, the system is thought to play an important role in the production of lymphocytes and antibodies and in phagocytosis. The system also transports lymph fluids, microorganisms, and protein back to the cardiovascular system and absorbs fat and fat-soluble substances from the intestine.

Lymph enters open-ended ducts called capillaries. The capillaries form larger collecting ducts, which drain into tissue centers or nodes. Lymph from the nodes eventually drains into the venous system by way of even larger ducts.

Lymph nodes, the most numerous element in the lymphatic system, rarely occur singly, but usually in chains or clusters. The lymph nodes that are closer to the center of the body are usually smaller; thus cervical nodes are larger than axillary nodes. The spleen is composed of lymphoid and reticuloendothelial cells. It is found under the ribs in the upper left quadrant of the abdomen. The amount of lymphoid tissue and the size of the lymph nodes vary with age. Infants have a small amount of palpable lymphatic tissue, which gradually increases until middle childhood, when the volume of lymphatic tissue reaches its peak. By middle adolescence the volume of lymphatic tissue begins to diminish, until it reaches the adult level of 2% to 3% of total body weight. Children are more likely to develop generalized adenopathy in response to disease, and even mild infections result in swollen nodes or “swollen glands.”