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为了维持生命,我们每天都要吃东西和喝水,同时也离不开阳光和空气。在食物里含有身体不可缺少的养分,吃下去的食物,在胃和肠子里消化以后,养分就被血液吸收,经过血液循环,分送到身体的各个组织器官里,供给它们活动的需要。血液除了输送养分以外,还把各个组织器官所产生的废物带走。空气里含有大量的氧气;肺在呼吸的时候,把空气里的氧气吸进来,经过血液循环送到各个组织;组织里产生的二氧化碳,又被血液带回肺脏,然后排出体外。从这里可以知道,血液循环是我们身体里的一个重要的运输过程。血液里含有很多水分,所以才能在血管里流动。身体各组织细胞也都含有不少水分,所以水和食物、空气同样是维持生命所不能缺少的。人们的吃喝对维持生命固然很重要,可是,身体里的废物如果排泄不出来,也难以生存下去。食物的渣滓是从直肠排出的,身体里产生的二氧化碳是从肺里呼
In order to sustain life, we eat and drink water every day, but also inseparable from the sun and the air. In the food contains the body essential nutrients, food to eat, after digestion in the stomach and intestines, the nutrients are absorbed by the blood, through the blood circulation, distributed to the various tissues and organs of the body, to provide them with the activities of the need. In addition to delivering nutrients, blood also removes wastes from various tissues and organs. The air contains a lot of oxygen; the lungs breathe in, the oxygen in the air sucked in, through the blood circulation to each organization; tissue generated in the carbon dioxide, the blood was brought back to the lungs, and then excreted. From here you can see that the blood circulation is an important transport process in our body. The blood contains a lot of water, so it can flow in the blood vessels. The body’s cells also contain a lot of water, so water and food, the air is also indispensable to maintain life. It is important for people to eat and drink to sustain their lives, but if the body’s waste can not be excreted, it will be hard to survive. The dregs of food are discharged from the rectum, and the carbon dioxide produced in the body is exhaled from the lungs