LYMPHATIC SYSTEM DR. NAWAL FOUAD It is a system which returns the lymph to the blood stream The lymph: is a clear colorless fluid which is formed at the tissue spaces. It is composed of: 1-Blood plasma which is not taken up by the venous capillaries. 2- Proteins from the tissues 3- Lymphocytes The lymphatic system is composed of A- Lymphatic tissue : Is a type of connective tissue that contains large numbers of lymphocytes. It is classified into: a- Lympatic aggregations b- Lymph nodes. a-Lympatic aggregations: It is found in the following organs or structures: Thymus. Spleen. Lymphatic nodules in close relation to epithelium of the alimentary canal e.g., tonsils, appendix, Peyer’s patches of the ileum. b-Lymph nodes: These are localised bean like collections of lymphoid tissue which interrupt the course of the lymphatics. They are present singly or in groups in specific locations in the body. Functions of lymph nodes: Production of antibodies by the lymphocytes. They pick up bacteria and antigens (by their phagocytic cells) preventing them from reaching the blood i.e., they act as filters B- Lymphatic vessels: The lymphatic vessels lie either superficial to deep fascia (superficial vessels) or deep to deep fascia (deep vessels). The latter usually follow the blood vessels. The superficial and deep lymphatic vessels always communicate. They assist the cardiovascular system in removal of tissue fluid from the tissue spaces of the body. The tissue fluid once it enters a lymphatic vessel is known as lymph. The lymphatic system is essentially a drainage system not a circulatory one. The lymph is drained from the tissues by the lymph capillaries which are larger than the blood capillaries ( to carry large protein molecules). The lymph capillaries unite to form small lymph vessels, which are collected to form large lymph vessels that possess numerous valves giving them a beaded appearance. The lymphatic vessels return the tissue fluid (lymph) to the blood after filtering it as it passes through at least one lymph node. The lymph vessels that carry lymph to a lymph node are known as afferent vessels, those that transport it away from the node are efferent vessels. The lymph reaches the blood stream at the root of the neck by large lymph vessels , in the right side, there is the right lymphatic duct. and in the left side, there is the thoracic duct. These ducts open into the veins of the root of the neck ,so all the lymph pours into the blood stream. Sites without Sites rich with lymphatics: lymphatics: • 1-The central 1-Dermis. nervous system. 2- Mucous • 2- Bone marrow. membranes. • 3- Spleen. • 4- Avascular 3- Serous structures membranes. (epidermis, articular 4- Glands. cartilages). Clinical notes: Obstruction of the lymphatics of a certain part leads to its oedema, e.g. in elephantiasis. The lymph nodes may become enlarged and painful if they receive infected lymph. Certain types of cancer prefer to send secondaries and spread via the lymphatics. As a result, the draining lymph nodes enlarge and form masses.