200103.vtt
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WEBVTT
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The body is mostly composed of fluids.
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All its cells contain and are surrounded by fluids.
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In addition, four to five liters of blood circulate
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through the cardiovascular system at any given time.
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Some of that blood escapes from the system as it passes through
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tiny blood vessels called capillaries in the body tissues.
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Fortunately, there is a "secondary circulatory system"
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that reabsorbs escaped fluid and returns it to the veins.
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That system is the lymphatic system.
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It runs parallel to the veins and empties into them.
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Lymph forms at the microscopic level.
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Small arteries, or arterioles, lead to capillaries,
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which in turn lead to small veins, or venules.
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Lymph capillaries lie close to the blood capillaries,
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but they are not actually connected.
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The arterioles deliver blood to the capillaries from the heart,
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and the venules take blood away from the capillaries.
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As blood flows through the capillaries it is under pressure.
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This is called hydrostatic pressure.
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This pressure forces some of the fluid in the blood
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out of the capillary into surrounding tissue.
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Oxygen from the red blood cells,
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and nutrients in the fluid then diffuse into the tissue.
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Carbon dioxide and cellular waste products in the tissue
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diffuse back into the bloodstream.
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The capillaries reabsorb most of the fluid.
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The lymph capillaries absorb what fluid is left.
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Edema, or swelling, occurs when fluid in or
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between the cells leaks into the body tissues.
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It is caused by events that increase the flow of fluid
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out of the bloodstream or prevent its return.
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Persistent edema may be a sign of serious health problems
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and should be checked by a health care professional.
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The lymphatic system can play a very worrisome role in the spread of breast cancer.
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Lymph nodes filter the lymph as it passes through the system.
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They are located at specific points throughout the body
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such as in the armpits and high in the throat.
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Lymphatic circulation in breast tissue helps regulate the
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local fluid balance as well as filter out harmful substances.
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But the breast's lymphatic system can also spread diseases
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such as cancer through the body.
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Lymphatic vessels provide a highway along
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which invasive cancerous cells move to other parts of the body.
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The process is called metastasis.
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It can lead to the formation of a secondary cancer mass in another part of the body.
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This mammogram shows a tumor and the lymph vessel network it has invaded.
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No woman is too young to know that regular breast self-examinations can
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help to catch tumors earlier in their growth, hopefully before they spread or metastasize.