The Lymphatic System

What is the lymphatic system? An extensive drainage network that helps keep bodily fluid levels in balance and defends the body against infections. Together with lymphoid organs and tissues, provide the structural basis of the immune system

Lymphatic characteristics One way system to the heart Carries clean fluids back to the blood Drains excess fluid from tissues Lymph is a clear, watery fluid that contains protein molecules, salts, glucose, urea, and other substances — throughout the body. Removes antigens from the body and exposes antigens to the immune system Lymph may contain macrophages, viruses, bacteria, cellular debris and even traveling cancer cells. Exercise. Exercise helps to restore flexibility and strength, and improves drainage. Specific exercises will be recommended by your doctor and/or physical therapist. Bandage. Wearing a customized compression sleeve or elastic bandage may help to prevent an accumulation of fluid. Arm pump. Applying an arm pump often helps to increase the fluid flow in the lymphatic vessels and keeps the fluid from collecting in the arm. Diet. Eating a well-balanced diet and controlling body weight is an important part of treatment. Keep the arm raised. Keeping the arm raised above the level of the heart, whenever possible, allows gravity to help drain the accumulated fluid. Prevent infection. It is important to follow preventive measures, such as good skin care, to protect the affected arm from infection and skin breakdown.

What type of vessels make up the lymphatic system? Vessels are called lymphatics Thin walled and analogous to veins 2 large ducts Right lymphatic duct Thoracic duct Both empty into the right and left subclavian veins Drained by the right lymphatic duct Drained by thoracic duct

Lymphatic Organs Lymph nodes Spleen Thymus Tonsils Peyer’s patches

Lymph nodes Principal lymphoid organs of the body Most are bean shaped organs along lymphatic collecting vessels Up to 1 inch in size Grouped together at various parts of the body Clusters of both superficial LNs deep

Lymph nodes Superficial Deep Cervical Axillary Inguinal Tracheobronchial Aortic Iliac

Circulation in the lymph nodes Enters via afferent lymphatic vessels Travels through large subcapsular sinus and smaller sinuses Exits the node at the hilus via efferent vessels Afferent vessels Efferent vessels

Critical Thinking Question Why are there more afferent lymphatic vessels carrying lymph to the lymph nodes than there are efferent lymphatic vessels? Answer: Fewer efferent vessels, causing flow of lymph to stagnate, allowing lymphocytes and macrophages time to carry out functions

What function do lymph nodes have? Filter lymph macrophages destroy microorganisms and debris Immune system—lymphocytes are activated and mount an attack against antigens

Lymphangiogram

Spleen Largest lymphoid organ Filters blood (lymph nodes filter lymph) Filters blood of bacteria, viruses, and other debris (blood-borne antigens “white pulp” Removes and destroys worn out red blood cells (RBCs) Stores platelets Site of lymphocyte production and immune surveillance and response In fetus only: RBC are made in the spleen Susceptible to injury; splenectomy increases risk of bacterial infection some of the breakdown products of RBCs to the liver ..for example Fe, so that more RBCs can be made .The unusable portion of worn-out blood is excreted in bile. Platelets- Platelets are not cells cytoplasmic fragments of very large cells called megakaryocytes Function in the process of hemostasis or stoppage of bleeding Platelets have granules containing chemicals that act in the clotting process

Spleen

Thymus Differs from other lymphoid organs in important ways It functions strictly in T lymphocyte maturation T cells become Immunocompetent It does not directly fight antigens Size with age In infants, it is found in the inferior neck and extends into the mediastinum, where it partially overlies the heart Increases in size and is most active during childhood Stops growing during adolescence and then gradually atrophies

Critical Thinking Question Why does the thymus increases in size and is MOST active during childhood, stops growing during adolescence and then starts getting smaller? Answer: The thymus produces a large amount of T cells so by the time a person reaches puberty, the body has a lot of lymphocytes. The thymus also produces a variety of hormones and plays an important role in the development of immunologic competence in fetus and child.

Tonsils Simplest lymphoid organs Form a ring of lymphatic tissue around the pharynx Crypts trap and destroy bacteria and particulate matter

Mucosa-associated lymphoid tissue (MALT) Mucosal surfaces within the body are protected by the mucosal immune system consisting of the mucosa-associated lymphoid tissue or MALT An extensive diffuse system of small concentrations of lymphoid tissue found in various sites of the body such as the gastrointestinal tract, thyroid, breast, lung, salivary glands, eye, and skin to protect from foreign matter.

MALT Examples: GALT (gut-associated lymphoid tissue, such as the Peyer's patches in the lining of the small intestines, as well as the adenoids, tonsils, and appendix) BALT (bronchial-associated lymphoid tissue in the bronchi)