Composition of the Lymphatic System

Lymphatic Circulatory System

The lymphatic system is part of the circulatory system, comprising a network of inter-connected tubes known as lymphatic vessels that carry a clear fluid called lymph towards the heart.

The lymphatic organs play an important part in the immune system. The lymphatic system transports the white blood cells which are important in the immune response against pathogens.

Composition of the Lymphatic System

The lymphatic system is composed of lymph vessels, lymph ducts, lymph nodes and organs. The organs associated with the lymphatic system are the spleen and thymus. The spleen is the boundary between the blood and the lymphatic system. Knots of lymphatic tissue in the spleen add lymphocytes to the blood. The spleen also acts as a filter for the blood, and helps to destroy worn out red-blood cells. In the event of damage to the spleen, it can be removed and its functions will be carried out by the liver, the bone marrow and the lymph nodes.

Diagram of human lymphatic system.

Lymph vessels are located as a network throughout all tissues in the body. Lymph vessels assist the circulatory system and all the cells of the body by removing wastes, germs and excess water from the tissue fluid. Lymph vessels carry lymph fluid from the bottom of the body up towards the heart and also drains from the head and shoulders as well as the arms.

Muscle contractions help push the lymph fluid upwards, and valves prevent the lymph fluid from flowing backwards. Many lymph vessels eventually merge into two large lymphatic vessels, called lymphatic ducts which empty into veins in the neck. The thoracic duct collects from the left side of the body and the lower right side of the body and empties into the left subclavian vein. The right thoracic duct collects from the right arm, thorax, neck and head, and drains into the right subclavian vein.

Most of the disease-fighting function of the adult mammal is carried out by the lymph nodes which occur along the lymph ducts. Lymph nodes are small, irregularly-shaped masses through which lymph vessels flow. Clusters of nodes occur in the armpits, groin, and neck. Cells of the immune system line channels through the nodes and attack bacteria and viruses travelling in the lymph, so they basically act as tiny filters.

Interaction between lymphatic and cardiovascular circulatory systems.