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Lymphatic System

What is the Lymphatic System?
The lymphatic system is a network of lymphatic vessels, lymph nodes and lymphatic tissue. The cells of the body continuously exude a fluid called as lymph. This fluid is collected by the lymphatic system. This maintains the fluid balance of the body. The lymph collected by the lymphatic system is then returned to the blood whenever required.

How can we describe the lymphatic system?The lymphatic system can be divided into three major parts. These are the lymph nodes, lymph vessels and lymphatic tissue. Let us describe each in detail:

  • The lymph nodes : These are sac-like structures present throughout the network of the lymphatic system. The lymph node is packed with cells called as lymphocytes. These are white blood cells in the body which protect us from infection. These cells are produced in the thymus, bone marrow and spleen. The major lymph nodes of importance in the body are the lymph nodes in the neck (cervical lymph nodes) and the lymph nodes in the groin (inguinal lymph nodes).
    Structure of a lymph node : The lymph node is covered by a capsule of fibrous tissue. Inside it, a lymph node contains macrophages. Macrophages are specialized white blood cells that engulf foreign and dead material. The germinal center lies at the core of the lymph node. Here there is presence of white blood cells called as the lymphocytes. The lymph node contains spaces called as sinuses. The flow of lymph occurs through these spaces. During times of infection there is collection of foreign and dead matter by the lymph vessels. Therefore there is accumulation of this matter in the lymph node. This causes swelling of the node. Hence swollen lymph nodes are often taken as signs of infection.
  • The lymph vessels : These vessels have a thin wall that allows fluid from the surroundings (lymph) to enter inside. This flow of fluid into the thin vessel wall is in a single direction. Fluid cannot come out once it has entered the vessel. There is the presence of valves throughout the lymphatic system, which prevents the lymph from back-flowing. The lymph is moved throughout the lymphatics by means of muscular contractions.
  • Lymphatic tissue : This tissue is present in all the lymph nodes. It is also present in the small intestines where it is called as Peyer’s patch. The lymphatic tissue consists of a fine network of fibrous lymphatic tissue. In the mesh that is present, white blood cells are entangled. The lymphatic tissue is responsible protecting the body against infection.
  • Spleen :
    This is the largest lymphatic organ in the body and it manufactures certain types of white blood cells are monitored. It is a huge organ lying on the left of the abdominal cavity and is not prominent in normal people. The spleen is prominently felt in cases where there are increased blood lymphocytes level. E.g. malaria.