Lymph nodes are small glandular structures located in the course of lymph vessels. The lymph nodes are also called lymph glands or lymphatic nodes.
STRUCTUTRE OF LYMPH NODES
Each lymph node constitutes masses of lymphatic tissue, covered by a dense connective tissue capsule. The structures are arranged in three layers namely cortex, paracortex and medulla.
Cortex of lymph node consists of primary and secondary lymphoid follicles. Primary follicle develops first. When some antigens enter the body and reach the lymph nodes, the cells of primary follicle proliferate. The active proliferation of the cells occurs in a particular area of the follicle called the germinal center. After proliferation of cells, the primary follicles become the secondary follicle. Cortex also contains some B lymphocytes, which are usually aggregated into the primary follicles. Macrophages are also found in the cortex.
Paracortex is in between the cortex and medulla. Paracortex contains T lymphocytes.
Medulla contains B and T lymphocytes and macrophages. Blood vessels of lymph node pass through medulla.
FUNCTIONS OF LYMPH NODES
Lymph nodes serve as filters which filter bacteria and toxic substances from the lymph. The Functions of the lymph nodes are:
- When lymph passes through the lymph nodes, it is filtered, i.e. the water and electrolytes are removed. But, the proteins and lipids are retained in the lymph.
- Bacteria and other toxic substances are destroyed by macrophages of lymph nodes. Because of this, lymph nodes are called defense barriers.
APPLIED PHYSIOLOGY –
1) SWELLING OF LYMPH NODES:
During infection or any other processes in a particular region of the body, activities of the lymph nodes in that region increase. This causes swelling of the lymph nodes. Sometimes, the swollen lymph nodes cause pain. Most common cause of swollen lymph nodes is infection. Lymph nodes situated near an infected area swell immediately. When the body recovers from infection, the lymph nodes restore their original size gradually, in one or two weeks.
Causes for Lymph Node Swelling
- Skin infection of arm causes swelling of lymph nodes in armpit.
- Tonsillitis or throat infection causes swelling of lymph nodes in neck.
- Infection of genital organs or leg results in swelling of lymph nodes in groin.
- Viral infections such as glandular fever which affect the whole body cause swelling of lymph nodes in various parts of the body.
- Cancer in a particular region may spread into the nearby lymph nodes causing the swelling. Examples:
- Throat cancer may spread into lymph nodes in neck.
- Lung cancer may spread into lymph nodes in chest.
- Breast cancer may spread into lymph nodes in armpit.
- Intestinal cancer may spread into lymph nodes in abdomen.
- Lymphomas (cancer of lymphatic system) and leukaemia cause swelling of lymph nodes in many parts of the body.