LYMPHATIC SYSTEM

This system is responsible for the transport and returning of materials from the tissues of the body to the blood.

        The system comprises lymph capillaries, lymph vessels, lymphoid masses, lymph nodes, and lymph-the fluid which flows in the system.

  

  

    Lymph capillaries end blindly in the body tissues, where pressure from the accumulation of interstitial fluid or extracellular fluid forces the fluid into the lymph capillaries. When this fluid enters the lymph capillaries, it is called lymph. The lymph vessels empty in veins; so lymph is a fluid in transit between interstitial fluid and the blood.

        The intercellular spaces in the walls of the lymph vessels are larger than those of the capillaries of blood vascular system. So larger molecules, from the interstitial fluid can also enter the lymph capillaries.

        Lymph capillaries join to form larger and larger lymph vessels; and ultimately form thoracic lymph duct, which opens into subclavian vein. The flow of lymph is always toward the thoracic duct.

        In the intestine, the branches of lymph capillaries, within villi, are called lacteals.

        The flow of lymph is maintained by ;

        Activity of skeletal muscles, movement of viscera, breathing movements and the valves, which prevent back flow of lymph.

        Along the pathway, the lymph vessels have, at certain points, masses of connective tissues where lymphocytes are present; these are lymph nodes. Several afferent lymph vessels enter a lymph node, which drained by a single, efferent lymph vessels.

       Lymph nodes are present in the neck region, axilla and groin of humans.

        In addition, several lymphoid masses are present in the walls of digestive tract, in the mucosa and submucosa. The larger masses spleen and thymus, tonsils and adenoids are all lymphoid masses. These produce lymphocytes.

        There are the several functions performed by lymphatic system.

I)                   In an average person, about three litres more fluid leaves the blood capillaries than is reabsorbed by them each day. It returns this excess fluid and its dissolved proteins and other substances to the blood.

II)                 The lacteals of villi absorb large fat globules, which are released by interstitial cells after the products of digestion of fats are absorbed. After a fatty meal these fat globules may lake up 1% of the lymph.

III)              The lymphatic system helps defend the body against foreign invaders. Lymph nodes have lymphocytes and macrophages that destroy bacteria and viruses. The painful swelling of lymph nodes in certain diseases (mumps is an extreme example) is largely a result of the accumulation of dead lymphocytes and macrophages.

IV)              Just as the lymph nodes filter lymph, the spleen filters blood, exposing it to macrophages and lymphocytes that destroy foreign particles and aged red blood cells.