The Circulatory System

The Circulatory System - The Circulatory System...

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The Circulatory System Introduction The circulatory system consists of blood, a heart, and blood vessels. Functions of the Circulatory System The circulatory system functions with other body systems to provide the following: Transport of materials: Gasses transported: Oxygen is transported from the lungs to the cells. CO 2 (a waste) is transported from the cells to the lungs. Transport other nutrients to cells - For example, glucose, a simple sugar used to produce ATP, is transported throughout the body by the circulatory system. Immediately after digestion, glucose is transported to the liver. The liver maintains a constant level of glucose in the blood. Transport other wastes from cells - For example, ammonia is produced as a result of protein digestion. It is transported to the liver where it is converted to less toxic urea. Urea is then transported to the kidneys for excretion in the urine. Transport hormones - Numerous hormones that help maintain constant internal conditions are transported by the circulatory system. Contains cells that fight infection Helps stabilize the pH and ionic concentration of the body fluids. It helps maintain body temperature by transporting heat. This is particularly important in homeothermic animals such as birds and mammals. Blood Vessels heart arteries arterioles capillaries venules veins heart
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Arteries Arteries carry blood away from heart. Arteries have a thick, elastic layer to allow stretching and absorb pressure. The wall stretches and recoils in response to pumping, thus peaks in pressure are absorbed. The arteries maintain pressure in the circulatory system much like a balloon maintains pressure on the air within it. The arteries therefore act as pressure reservoirs by maintaining (storing) pressure. The elastic layer is surrounded by circular muscle to control the diameter and thus the rate of blood flow. An outer layer of connective tissue provides strength. Arterioles Smooth muscle surrounding the arteries and arterioles controls the distribution of blood. For example, blood vessels dilate when O 2 levels decrease or wastes accumulate. This allows more blood into an area to bring oxygen and nutrients or remove wastes. Capillaries The smallest blood vessels are capillaries. They are typically less than 1 mm long. The diameter is so small that red blood cells travel single file. The total length of capillaries on one person is over 50,000 miles. This would go around the earth twice. Not all of the capillary beds are open at one time because all of them would hold 1.4 times the total blood volume of the all the blood in the body. Vasodilation and vasoconstriction refer to the dilation and constriction of blood vessels. The diameter is controlled by neural and endocrine controls. Sphincter muscles control the flow of blood to the capillaries.
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This note was uploaded on 07/20/2011 for the course BIO 101 taught by Professor Krm during the Summer '11 term at LSU.

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The Circulatory System - The Circulatory System...

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