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人类在生产和生活的过程中,创造了无数完美的机械.然而,可能令你意想不到的是,世界上最完美的机械却是人体本身! 首先,人体有一套极其完美的液体传输系统.人体里有着大大小小的“河流”--血管,心脏好像一台永不停息的泵,推动着血液从左心室射出,经过动脉、毛细血管、静脉回到右心房. 血管有粗有细,毛细血管虽细, 分支却很多,它的总横截面积约为315 cm2,远远大于手主动脉的横截
In the process of production and living, humans have created countless perfect machines. However, what may surprise you is that the most perfect machinery in the world is the human body itself! First of all, the human body has an extremely perfect liquid transmission system. There are large and small “river” - blood vessels, the heart is like a never-ending pump, pushing the blood from the left ventricle, through the arteries, capillaries, veins back to the right atrium. Blood vessels are thick and thin Although the capillaries are fine and have many branches, the total cross-sectional area is about 315 cm2, which is far greater than the transverse diameter of the hand aorta.