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Unformatted text preview: Anatomy The Lymphatic System (Fig 23-1) Continuation of the cardiovascular system Composed of vessels Have same layers as arteries and veins Tunica interma Tunica media Tunica externa Delivers lymph Lymph: excess tissue fluid, interstitial fluid • Similar to plasma but lacks cells and proteins, only the fluid • Plasma forms tissue fluid which forms lymph returns fluid to the blood vascular system no pressure system 2 cell types 1. Lymph Cells/Lymphocytes • Most important • One of the white blood cells • Produced by lymphatic system • Some produced in bone marrow 2. Macrophages • Large phagocytic cells Structures Categorized into 1. Lymphatic tissue 2. Lymphatic organs Monitor, alter, and filter lymph • Filtration probably most important Specific stem cells are present which help to produce the lymphocytes Lymphoid tissues Tonsils Galt Lymphoid Organs Thymus Spleen Lymph nodes Three major functions 1. To maintain blood volume • Adds fluid back into plasma to keep the volume of plasma at a certain level 2. Homeostasis • Maintenance of chemical levels within the body 3. Production and distribution of lymphocytes • Play a role in our immunological system Vessels start out with capillaries: lymphatic capillaries or terminal lymphatics Capillary beds associated with these Lymphatic capillaries differ from blood capillaries (Fig 23-2) Blind ended, not connected to anything • Not a circulatory system Larger diameter than other capillaries Thinner walled • No basement membrane • Cells connected to one another very loosely Usually look collapsed • b/c no pressure to keep them open still endothelium like blood capillaries overlap and can open quite wide to act like a one way valve • fluid outside the capillary passes through valves into the lymphatic capillaries • bacteria and viruses can get into the lymphatic capillary ♦ macrophages help to get rid of the bad things that get into capillary very permeable, more so than blood capillaries • allow fluid to pass very readily COP: colloid osmotic pressure • Can’t draw all fluid in, only gets ~90%, 10% needs to be picked up and carried back to the blood vascular system by lymphatic system 72% of blood plasma is filtered out into tissue spaces per day (3.6 liters approx.) • At any point in time there is always ½ a liter of tissue fluid in your body As new fluid is pushing out, it washes the old fluid away, always a turnover • Allows for exchange between cells If tissue fluid isn’t pulled out, we get swelling....
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