routes. They are especially prevalent in areas around the armpits (axillary nodes), groin (inguinal node), neck (cervical nodes), and knees (popliteal nodes). The nodes contain lymphocytes, which enter the bloodstream via specialized vessels called the high endothelial venules.
T cells congregate in the inner cortex (paracortex), and B cells are organized in germinal centers in the outer cortex. Lymph, along with antigens, drains into the node through afferent (incoming) lymphatic vessels and percolates through the lymph node, where it comes in contact with and activates lymphocytes.
Activated lymphocytes, carried in the lymph, exit the node through the efferent (outgoing) vessels and eventually enter the bloodstream throughout the body.
When there is an infection, these nodes swell up due to a buildup of lymph fluid, bacteria or other organisms, and immune system cells.
The lymphoid system includes several types of cells—for example, reticular cells and white blood cells such as macrophages and lymphocytes. Reticular cells provide structural support since they produce and maintain the thin networks of fibers that are a framework for most lymphoid organs. Macrophages help eliminate invaders by engulfing foreign materials and initiating the immune response. These cells may be embedded in one place, such as lymph nodes, or wander in the loose connective-tissue spaces. Lymphoid tissue has a central role in metastasis, the process by which cancer cells spread to tissues distant from the site of tumor origin. This is because of the proximity of lymph vessels to tumor masses in organs or other tissues.
The most common cell type in the lymphoid tissue is the lymphocyte. Like macrophages, lymphocytes are formed from stem cells in the bone marrow and then transported in the blood to the lymphoid tissue. T lymphocytes mature in the thymus before proceeding to the other lymphoid organs, such as the spleen. B lymphocytes mature in the bone marrow, then go directly to the lymphoid organs. Both T and B lymphocytes play a key role in immune responses to infectious microorganisms.
Swollen lymph nodes can be a symptom of numerous conditions:
• Glandular fever: Also known as infectious mononucleosis, or mono, is common among teenagers, college students, and young people. It can cause long-lasting swelling, a sore throat, and fatigue. Malnourishment, a poor diet, and the Epstein-Barr virus (EBV), a highly contagious herpes virus, contribute to this illness.
• Tonsillitis: This is more common in children on a junk food diet than in adults. It occurs when the lymph nodes at the back of the mouth fight bacterial or viral infections. Sugar breeds bacteria. The body produces viruses to assist in the removal of bacteria and other toxins. A sugar-free diet is the best prevention for this illness.
• Pharyngitis: Some people refer to this infection as “strep throat.” It results from a streptococcus bacterial infection and can cause lymph nodes to swell. Again, avoiding refined sugar and sugar products can prevent this illness.
• Cancer: Lymph nodes capture cancer cells. Thus, lymph nodes may become sites of secondary tumor formation. Cancer that starts in the lymphatic system is known as lymphoma. It is the most dangerous lymphatic disease.
Hodgkin lymphoma most commonly affects lymph nodes in the upper part of the body, such as the neck, chest, and arms.
Hodgkin lymphoma affects B lymphocytes,