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KamleshKrGupta
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The defining characteristic of the human heart is its tireless beating, a constant rhythmic contraction to life that serves the all-important purpose of circulating blood through our bodies. Each heartbeat pushes blood along a one-way path, through increasingly narrow arteries leading away from the heart, across the intricate networks of capillary beds in tissues, and into increasingly wide veins that eventually return the blood to the heart. In the average adult at rest, blood completes a full circuit around the body-from the heart and back again-in just one minute. During that time, oxygen and nutrients are delivered to tissues, in exchange for waste products such as carbon dioxide, which are picked up for removal from the body. This exchange process is constant, with freshly oxygenated blood coursing continuously into tissues, deoxygenated blood being pushed away, nutrients being absorbed from the digestive tract, and waste products being filtered out by the renal and hepatic circulation.