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| | Hemoglobin - MSN Encarta |
 | | Hemoglobin controls the expansion and contraction of blood vessels, and thus blood pressure, by regulating the amount of nitric oxide to which the vessels are exposed. |
 | | Hemoglobin is contained entirely in the red blood cells, amounting to perhaps 35 percent of their weight. |
 | | After a life of perhaps 120 days, red blood cells are destroyed in the spleen, or in the course of circulation, their hemoglobin is broken into its constituents, including iron, which enters new blood cells formed in the bone marrow. |
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