Lymph nodes

A lymph node is a small gland involved in the body's lymphatic system, the disease-fighting network spread throughout your body. The lymphatic system also includes the lymphatic vessels, tonsils, adenoids, spleen, thymus and bone marrow.

Size and location

In its normal state a lymph node is the size and shape of a small bean but much softer.   They are all over the body but the greatest concentration is in the head and neck area. There are approximately 150 lymph nodes on each side of the neck with most associated with the internal jugular vein on each side.

Function

Lymph nodes function as the immune system's immigration control and forts. They are there to detect and destroy alien invaders.

Lymph is watery straw-coloured fluid that escapes from blood vessels into the body tissues. You could think of it as an overflow of fluid from the blood vessels and it contains small white blood cells called lymphocytes amongst other things. Lymph also picks up loose material including bacteria and viruses from the tissues.

The lymphoctes act like policemen or immigration officers patrolling an area. They detect unhealthy and foreign cells. The lymph is then drained from the tissues much like rainwater is drained away by a guttering system called lymph vessels or the lymphatics. The lymphatic vessels join up into larger and larger vessels and ultimately empty lymph back into the blood via the internal jugular vein. Along the way, the lymphatics pass through small filtering stations... the lymph nodes. To enter a lymph node is a bit like entering passport control at an airport. Every cell is checked to determine whether it has the credentials to exist in the body. A foreign cell like a bacterium will be detected and cause the lymphocytes in the local lymph node to multiply and to return to the site of infection to fight the invaders much like a unit of immigration officials is mobilised. Lymphocytes also release chemical signals that increase blood flow into the area which increases the number of lymphocytes and chemicals arriving to destroy the foreign cells. This is associated with redness, swelling, and tenderness at the site of invasion and also in the local lymph node. This state is known as inflammation and persists until the targeted cells are destroyed.

Lymphocytes exist either as B cells or T cells. B cells fight infection indirectly by producing plasma cells, which in turn produce antibodies that neutralize foreign invaders. It is as if they " put out a contract " and facilitate the kill. T cells are "enforcers" or "hitmen" and kill foreign invaders directly.

home...