Lymph nodes

Synonyms for lymph nodes

Lymph gland Medical = Nodus lymphaticus, Nodus lymphoideus English = lymph node

Definition

Lymph nodes are filter stations of the lymphatic system in the body, which transports fluid released from the blood vessels into the tissue back into the bloodstream. The lymph nodes purify this fluid, the lymph, and also play a role in the defense against germs. They are a part of the lymphatic system.

Anatomy of the lymph nodes

Lymph nodes are kidney-shaped organs of 2 mm to 2 cm in size that are found throughout the body, for example in the neck, groin, armpits or neck. The lymph node is surrounded by a capsule of connective tissue through which several feeding lymph vessels (vasa afferentia) enter. At the so-called hilus, a lymph vessel (vas efferens) leaves the organ and the blood vessels (arteries and veins) enter or leave.

A distinction is made between regional and collective lymph nodes. Regional lymph nodes collect the lymph of a body area (e.g. the neck). Collective lymph nodes are located downstream and filter the already purified lymph from several regional lymph nodes.

The microscopic structure of a lymph node is three-layered and is divided into the outer cortex, the paracortical area and the inner medulla. The whole is surrounded by the connective tissue capsule, from which runners (trabecula) extend into the interior of the lymph node. The layers of the lymph node are penetrated by the lymph sinus.

These are spaces in which the lymph makes its way into the lymph node until it leaves the lymph node at the hilus. Depending on the location, a distinction is made between the marginal sinus, which is located directly under the capsule, the intermediate sinus, which runs through the cortex and paracortex, and the medullary sinus, which is located in the medulla. The supplying lymphatic vessels lead into the marginal sinus and the vas efferens emerges from the medullary sinus.

Furthermore, depending on the layer, different cells are found in the lymph node tissue. In the cortex there are roundish accumulations (follicles) of B-lymphocytes, a certain form of white blood cells. Another form of white blood cells, the T-lymphocytes, are found in the paracortical zone.

Finally, activated B-lymphocytes and macrophages are found in the medulla. The lymph nodes fulfill several functions. Firstly, they serve to activate, multiply and store defense cells, the B and T lymphocytes.

In addition, after activation by germs contained in the lymph, the contained cells produce antibodies, which are subsequently released into the bloodstream to fight the pathogens. Furthermore, the lymph nodes act as filters of the lymph fluid, i.e. they free it from:

  • Pathogens
  • Foreign bodies (e.g. soot particles) or
  • Tumor cells.
  • What are B lymphocytes?
  • Lymph Vascular System