Lymph nodes are small glandular structures located in the course of lymph vessels. The lymph nodes are also called lymph glands or lymphatic 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.

1) Cortex:

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.

2) Paracortex:

Paracortex is in between the cortex and medulla. Paracortex contains T lymphocytes.

3) Medulla:

Medulla contains B and T lymphocytes and macrophages. Blood vessels of lymph node pass through medulla.


Lymph nodes serve as filters which filter bacteria and toxic substances from the lymph. The Functions of the lymph nodes are:

  1. 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.
  2. Bacteria and other toxic substances are destroyed by macrophages of lymph nodes. Because of this, lymph nodes are called defense barriers.



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

  1. Skin  infection  of  arm  causes  swelling  of  lymph  nodes in armpit.
  2. Tonsillitis  or throat infection causes swelling  of lymph nodes in neck.
  3. Infection  of  genital  organs  or  leg  results  in  swelling of lymph nodes in groin.
  4. Viral  infections  such  as  glandular fever  which  affect the whole  body cause swelling  of lymph nodes in various parts of the body.
  5. 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.

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