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  3. How Are Our Bodies Made? The human body is like a complicated machine made of many interconnected parts. At the smallest sca

How Are Our Bodies Made? The human body is like a complicated machine made of many interconnected parts. At the smallest sca

admin2015-01-13  85
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答案 How Are Our Bodies Made? The human body is like a complicated machine made of many interconnected parts. At the smallest scale, the body is composed of about 100 trillion tiny living cells. There are different kinds of cells, each with its own task to do. For example, nerve cells carry messages of sensations and pain to the brain. Groups of similar cells are organized together to make tissues, such as skin and muscle. In turn, various types of tissues combine to form organs. Among the body’s major organs are heart, brain, stomach, and kidneys. Finally, groups of organs and other body parts work together as organ systems. The immune system, for example, is a complicated mass of organs and chemicals whose job is to combat infection and diseases. The heart and veins make up circulatory blood system, which keeps blood flowing around the body.
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