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人体在生命活动过程中,需要大量的氧气和营养物质。这些物质通过心血管系统来运送,供给人体的各个器官和组织。心血管系统是一个闭锁的、连续性的管道系统,它包括有心脏、动脉、静脉和毛细血管,血液在血管内沿一定方向流动,形成血液循环。心脏是血液循环的动力器官,起着“抽水机”或“唧筒”样的作用,舒张时吸回血液,收缩时则推送血液从心脏进入动脉,又经过小动脉到达毛细血管。在毛细血管,血液与组织间进行物质交换(包括氧与二氧化碳,营养
The human body needs a lot of oxygen and nutrients during the life activities. These substances are transported through the cardiovascular system and supplied to various organs and tissues of the body. Cardiovascular system is a closed, continuous pipeline system, which includes the heart, arteries, veins and capillaries, blood flow in the blood vessels in a certain direction, the formation of blood circulation. The heart is the blood circulation of the dynamic organs, plays a “pump” or “pump” -like role, diastolic blood back to the contraction when the blood is pushed from the heart into the artery, and then through the arterioles to the capillaries. In the capillaries, blood and tissue exchange of substances (including oxygen and carbon dioxide, nutrition