Knowledge - Students will be able to describe:
It is estimated that there are approximately 500 lymph nodes in the human body. They are ovoid or bean shaped lymphoid organs that drain specific regions of the body and are connected to the circulation through afferent and efferent lymphatics. The location of each group of lymph nodes in the human body is relatively constant. They vary in size from 2mm to 15mm. There are peripheral nodes that may be seen or easily palpable. Eg: Head and neck nodes (areas of active antigenic stimulation) or the deeper group of nodes that are not palpable, but can cause symptoms when enlarged and can be seen only on x-rays, CT scans. Eg: Mediastinal, retroperitoneal or pelvic nodes. The major function of lymph nodes are lymphopoiesis, filtration of lymph, and processing of antigens, viral, bacterial, etc. All lymph finally enters the circulation through the thoracic duct.
Lymph nodes comprise the B and T cell populations and plasma cells; each with multiple subpopulations. Each of these cell populations can be stimulated by antigens, bacteria and viruses resulting in enlarged lymph nodes that can be seen and are palpable on routine physical examination. Or, one may encounter enlarged lymph nodes in the deeper chains on x-ray, chest or CT scans. A parent, a patient, or a physician may observe an enlarged lymph node that may cause concern. This enlargement could be generalized from non-specific stimulation, or localized enlargement from an inflammatory process, or a neoplastic process in the area of drainage.
The student should take a systematic step-by-step approach and come to a clinical conclusion, by careful history, physical examination, laboratory tests, x-rays and CT scans, when necessary. The student should also learn when observation alone is prudent and when to proceed with an F.N.A. (fine needle aspiration) or biopsy of an enlarged lymph node.