The Cardiac/Circulatory System
Introduction
The main function of the cardiovascular system is to deliver oxygen to all other organs and systems of the body and to remove waste gases, such as carbon dioxide, which is produces when the oxygen is used up.
The cardiac/circulatory system consists of:
Blood and blood elements
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Blood is one of the connective tissues of the body. It is a sticky, opaque fluid with both solid and liquid components. Living blood cells, the formed elements, are suspended in a nonliving fluid called plasma. Plasma is more than 90 percent water.
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There are three formed elements in the blood: red blood cells, platelets, and white blood cells.
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The oxygen-carrying elements of blood are the red blood cells (RBC's), which are formed in the bone marrow. They pick up oxygen in the lungs and release it in the capillaries (see below) to tissues and cells. RBCs are also called erythrocytes.
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RBCs can't reproduce themselves. They have a fairly short useful life.
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RBCs circulate for about 120 days until defective and are then removed from the blood by the spleen.
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Platelets, another formed element in the blood, are cell fragments that aid in blood clotting. They are also called thrombocytes.
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White blood cells are the third formed element in the blood. They are important in the immune system. Another name for them is leukocytes.