Lymphatic System and Immunity Courtney Shelton CST, BA ST 120

Objectives Day 1 Discuss the structure and function of the lymphatic system Discuss and locate the thymus gland, spleen, and tonsils Identify diseases and disorders of the lymphatic system

Immune System The “safety net” that protects us from potentially harmful toxins, disease-causing bacteria, viruses, and cells in our body that have turned cancerous.

The Lymphatic System We know that the circulatory system brings many needed substances to cells and then removes the waste products. Some substances cannot enter or return through the capillary walls, including excess fluid and protein molecules.

Lymph and Lymphatic Vessels This excess fluid and protein molecules are returned to the blood as lymph. Lymph is a specialized fluid formed in the tissue spaces that is transported by way of specialized lymphatic vessels to eventually reenter the circulatory system.

How does lymph form? Blood plasma filters out of the capillaries into the spaces between tissue cells because of the pressure generated by the heart. There the fluid is called interstitial fluid Most interstitial fluid goes back into the capillaries. The remainder of the interstitial fluid enters the lymphatic system before it returns to the blood.

Lymph The lymph then enters the lymphatic capillaries which permits excess tissue fluid and protein molecules to leave the tissue space. What would happen if this fluid was NOT permitted to leave the tissue space?

Lymphatic Capillaries vs. Blood Capillaries Similar to one another Microscopic Single sheet of simple squamous epithelium called endothelium Different from one another The “fit” between the endothelial cells in lymphatic vessels is larger to allow larger substances to pass Movement of lymph is one way. Blood moves in a circular route.

Lymph Lymph flows into successively larger and larger vessels called lymphatic venules and veins Eventually empties into two terminal vessels Right lymphatic duct Thoracic duct

Thoracic duct Largest duct The thoracic duct in the abdomen has a pouchlike structure used for storing lymph called the cisterna chyli

Lymph Nodes Lymph is filtered by moving through these nodes as it moves from its origin in the tissue spaces to the thoracic or right lymphatic ducts and then into the venous blood. Nodes are located in clusters Function of nodes is defense and white blood cell formation

Biological Filtration A process in which cells alter the contents of the filtered fluid to prevent local infections from spreading. Lymph enters the node through 4 afferent lymph vessels Lymph flows through lymph spaces called sinuses that surround nodules found in the outer and inner areas of the node

Filtration, cont’d In passing through the node, lymph is filtered so that particles such as bacteria and cancer cells are removed and prevented from entering the blood. Lymph exits through a single efferent lymph vessel.

Axillary nodes Surgeons remove lymph nodes in the armpit to ensure the removal of any cancer cells that may have been filtered out of the lymph drained from the breast.

Thymus Small lymphoid tissue organ located in the mediastinum, extending upward into the neck Largest at puberty Plays a critical role in the body’s vital immunity mechanism

Thymus It is a source of lymphocytes before birth and is then especially important in the development of T cells Completes most of its work in early childhood and is then replaced with fat and connective tissue in a process called involution.

Tonsils Located in a protective ring under the mucous membranes in the mouth and back of the throat Help protect against bacteria that may invade tissues in the area around the openings between the nasal and oral cavities

Tonsils Palatine tonsils are on each side of the throat Pharyngeal tonsils a.k.a adenoids are near the posterior opening of the nasal cavity Lingual tonsils are near the base of the tongue

Spleen Largest lymphoid organ in the body Located high in the upper left quadrant of the abdomen lateral to the stomach Blood enters the spleen then flows through dense, pulplike accumulation of lymphocytes

Function of the Spleen As blood flows through the pulp, the spleen removes by filtration and phagocytosis many bacteria and other foreign substances, destroys worn out RBC’s and salvages the iron found in hemoglobin for future use, and serves as a reservoir for blood that can be returned to the circulatory system when needed.

Questions????