Lymph Outline

Lymph Outline - Chapter 22: The Lymphatic System...

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Chapter 22: The Lymphatic System Organization of the Lymphatic System, p. 764 The lymphatic system has 4 main parts: 1. lymph : a fluid similar to plasma, but without the plasma proteins. 2. lymphatic vessels (lymphatics ): the network that carries lymph from peripheral tissues to the venous system. 3. lymphoid tissues and lymphoid organs : found throughout the body. 4. lymphocytes , phagocytes and other immune system cells. Functions of the Lymphatic System, p. 764 The main function of the lymphatic system is to produce, maintain and distribute lymphocytes . Lymphocytes are produced and stored in lymphoid tissues (such as the tonsils), and lymphoid organs (such as the spleen and thymus), and are also produced in red bone marrow. To function, the lymphocytes must detect problems and travel to the site of injury or infection. Lymphocytes circulate in the blood, enter the interstitial fluid through capillaries, and return to the blood stream through lymphatic vessels. The circulation of fluids from blood plasma to lymph and back to the venous system also transports other immune system cells (such as macrophages and microphages) as well as hormones, nutrients and waste products. Lymphatic Vessels, p. 765 The vessels that carry lymph are lymphatic vessels . The lymphatic system begins with the smallest vessels: the lymphatic capillaries (terminal lymphatics ). Lymphatic capillaries differ from blood capillaries in 4 ways: 1. They start as pockets rather than tubes. 2. They have larger diameters. 3. They have thinner walls. 4. In section, they are flat or irregular. The endothelial cells of lymphatic capillaries are not tightly bound together, but they overlap. The overlap acts as a one-way valve that allows fluids, solutes and larger materials such as viruses, bacteria and debris to enter the vessel, but prevents them from returning to the intercellular space. Special lymphatic capillaries (lacteals ) in the small intestine transport lipids from the digestive tract. From the lymphatic capillaries, lymph flows into a system of larger lymphatic vessels similar to veins, containing many one-way valves that give lymph vessels a lumpy, beaded appearance. Lymphatic vessels often travel toward the thoracic cavity in association with veins, but are generally smaller. From the lymphatic capillaries, the lymphatic system is divided into the superficial lymphatics and deep lymphatics . The superficial lymphatics are located in the skin, mucus membranes, and serous membranes lining body cavities. The deep lymphatics are larger vessels that accompany deep arteries and veins. The superficial lymphatics and deep lymphatics join to form the large lymphatic trunks that empty into 2 major collecting vessels: the thoracic duct and the right lymphatic duct . The base of the thoracic duct
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Lymph Outline - Chapter 22: The Lymphatic System...

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