血液四级英语作文

血液四级英语作文

Blood

What is blood? It is the red liquid which comes out of your finger when you cut it because of not being careful.There are about 13 pints (品脱) of blood in a man＇s body. He can give a pfnt of blood at a time to a blood bank for the use o other man who may need it. A healthy body makes up the pint of blood quickly.

What does our blood do for us? It takes food to all parts of our bodies and takes waste away from them. All the parts of our bodies are made up of cells, these cells, which are very small, all need food all the time. The blood is like a stream.The cells take what they need out of the blood stream, as plants and fishes take their food out of water.The blood stream carries food and the oxygen which it has taken up in our lungs to all the cells in the body.

What makes the blood go on moving round the body in a stream? The heart sends it round. The heart keeps a stream of blood going all around the body and back again to itself. Everywhere the blood stream does two things: supplies the cells with food and oxygen and takes away waste. It is as if the blood kept the little fires in cells burning and took away the ashes.

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这篇说明文向我们描述了血液是什么，血液的作用以及是什么促使血液循环于我们全身。读者可将此文作为背景知识来学习。

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血液

什么是血?血就是当不小心割破了手指时，从中流出的红色的液体。人体内大约有13品脱血液。他可以一次献给血库1品脱血。而这些血对于一个身体健康的人来说，很快就可以补充上。

血是做什么用的?它将食物送到我们身体的各个部分，然后又将其中的废物排出。我们体内的各个系统都是由细胞组成的。这些微小的细胞总是需要食物。血液就像一条小溪。这些细胞，就象植物和鱼从水中提取食物一样，从血液中提取它所需要的.食物。血液将这些食物以及从肺中提取的氧转送到体内各个器官的细胞中。

是什么使得血液在体内四处活动?是心脏。是心脏使血液在体内循环。每到一处，血液要做两件事：供给食物和氧，排出废物。好像是血液使得体内的小火一直燃烧着，然后又将烧过的灰排出。